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Nature vs. nurture debate: 50-year twin study proves it takes two to determine human traits.

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A culmination of more than half a century of research collected on 14.5 million pairs of twins has finally concluded that the nature versus nurture debate is a draw. According to the plethora of data, both have nearly identical influences on a person’s behavior, which suggests we need to stop looking at ourselves as a result of nature versus nurture, and instead realize we are a combination of both.

The recent study , published in the journal Nature Genetics , is the result of the collaboration between Dr. Beben Benyamin from the Queensland Brain Institute and researchers at the VU University of Amsterdam. They reviewed nearly every twin study ever done in the past 50 years. The impressive global twin review revealed that, on average, the variation for human traits and diseases is split almost equally.

“When visiting the nature versus nurture debate, there is overwhelming evidence that both genetic and environmental factors can influence traits and diseases,” Benyamin said in the press release . “What is comforting is that, on average, about 50 percent of individual differences are genetic and 50 percent are environmental.

The finding did not ring true for every case, however, as certain conditions leaned way more than others. For example, in the case of bipolar disorder, this was found to be around 70 percent genetic and only 30 percent due to environmental factors.

Although the finding may be unsatisfying for those hoping that one side of the spectrum held more weight than the other, according to Benyamin, the findings have “implications for choosing the best strategy to find genes affecting disease.” The data may also change the way that scientists approach the study of genetics. In about 69 percent of the cases, the twins' individual traits ended up being the cumulative effect of genetic differences.

“This means that there are good reasons to study the biology of human traits, and that the combined effect of many genes on a trait is simply the sum of the effect of each individual gene,” Benyamin explained.

Twin studies have been an integral part of science because of the unique genetic similarities between twin siblings. Identical twins develop from a single fertilized egg and they have the same genome. This means that any differences between the twins are due to their environment, not their genetics . For nearly a century scientists have used twin studies to better understand the extent to which certain traits are inherited.

Source: Polderman TJC, Benyamin B, de Leeuw CA, van Bochoven A, Visscher PM, Posthuma D. Meta-Analysis of the Heritability of Human Traits based on Fifty Years of Twin Studies. Nature Genetics. 2015.

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Nature vs. Nurture Debate In Psychology

Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

On This Page:

The nature vs. nurture debate in psychology concerns the relative importance of an individual’s innate qualities (nature) versus personal experiences (nurture) in determining or causing individual differences in physical and behavioral traits. While early theories favored one factor over the other, contemporary views recognize a complex interplay between genes and environment in shaping behavior and development.

Key Takeaways

• Nature is what we think of as pre-wiring and is influenced by genetic inheritance and other biological factors.
• Nurture is generally taken as the influence of external factors after conception, e.g., the product of exposure, life experiences, and learning on an individual.
• Behavioral genetics has enabled psychology to quantify the relative contribution of nature and nurture concerning specific psychological traits.
• Instead of defending extreme nativist or nurturist views, most psychological researchers are now interested in investigating how nature and nurture interact in a host of qualitatively different ways.
• For example, epigenetics is an emerging area of research that shows how environmental influences affect the expression of genes.

The nature-nurture debate is concerned with the relative contribution that both influences make to human behavior, such as personality, cognitive traits, temperament and psychopathology.

Examples of Nature vs. Nurture

Nature vs. nurture in child development.

In child development, the nature vs. nurture debate is evident in the study of language acquisition . Researchers like Chomsky (1957) argue that humans are born with an innate capacity for language (nature), known as universal grammar, suggesting that genetics play a significant role in language development.

Conversely, the behaviorist perspective, exemplified by Skinner (1957), emphasizes the role of environmental reinforcement and learning (nurture) in language acquisition.

Twin studies have provided valuable insights into this debate, demonstrating that identical twins raised apart may share linguistic similarities despite different environments, suggesting a strong genetic influence (Bouchard, 1979)

However, environmental factors, such as exposure to language-rich environments, also play a crucial role in language development, highlighting the intricate interplay between nature and nurture in child development.

Nature vs. Nurture in Personality Development

The nature vs. nurture debate in personality psychology centers on the origins of personality traits. Twin studies have shown that identical twins reared apart tend to have more similar personalities than fraternal twins, indicating a genetic component to personality (Bouchard, 1994).

However, environmental factors, such as parenting styles, cultural influences, and life experiences, also shape personality.

For example, research by Caspi et al. (2003) demonstrated that a particular gene (MAOA) can interact with childhood maltreatment to increase the risk of aggressive behavior in adulthood.

This highlights that genetic predispositions and environmental factors contribute to personality development, and their interaction is complex and multifaceted.

Nature vs. Nurture in Mental Illness Development

The nature vs. nurture debate in mental health explores the etiology of depression. Genetic studies have identified specific genes associated with an increased vulnerability to depression, indicating a genetic component (Sullivan et al., 2000).

However, environmental factors, such as adverse life events and chronic stress during childhood, also play a significant role in the development of depressive disorders (Dube et al.., 2002; Keller et al., 2007)

The diathesis-stress model posits that individuals inherit a genetic predisposition (diathesis) to a disorder, which is then activated or exacerbated by environmental stressors (Monroe & Simons, 1991).

This model illustrates how nature and nurture interact to influence mental health outcomes.

Nature vs. Nurture of Intelligence

The nature vs. nurture debate in intelligence examines the relative contributions of genetic and environmental factors to cognitive abilities.

Intelligence is highly heritable, with about 50% of variance in IQ attributed to genetic factors, based on studies of twins, adoptees, and families (Plomin & Spinath, 2004).

Heritability of intelligence increases with age, from about 20% in infancy to as high as 80% in adulthood, suggesting amplifying effects of genes over time.

However, environmental influences, such as access to quality education and stimulating environments, also significantly impact intelligence.

Shared environmental influences like family background are more influential in childhood, whereas non-shared experiences are more important later in life.

Research by Flynn (1987) showed that average IQ scores have increased over generations, suggesting that environmental improvements, known as the Flynn effect , can lead to substantial gains in cognitive abilities.

Molecular genetics provides tools to identify specific genes and understand their pathways and interactions. However, progress has been slow for complex traits like intelligence. Identified genes have small effect sizes (Plomin & Spinath, 2004).

Overall, intelligence results from complex interplay between genes and environment over development. Molecular genetics offers promise to clarify these mechanisms. The nature vs nurture debate is outdated – both play key roles.

Nativism (Extreme Nature Position)

It has long been known that certain physical characteristics are biologically determined by genetic inheritance.

Color of eyes, straight or curly hair, pigmentation of the skin, and certain diseases (such as Huntingdon’s chorea) are all a function of the genes we inherit.

These facts have led many to speculate as to whether psychological characteristics such as behavioral tendencies, personality attributes, and mental abilities are also “wired in” before we are even born.

Those who adopt an extreme hereditary position are known as nativists.  Their basic assumption is that the characteristics of the human species as a whole are a product of evolution and that individual differences are due to each person’s unique genetic code.

In general, the earlier a particular ability appears, the more likely it is to be under the influence of genetic factors. Estimates of genetic influence are called heritability.

Examples of extreme nature positions in psychology include Chomsky (1965), who proposed language is gained through the use of an innate language acquisition device. Another example of nature is Freud’s theory of aggression as being an innate drive (called Thanatos).

Characteristics and differences that are not observable at birth, but which emerge later in life, are regarded as the product of maturation. That is to say, we all have an inner “biological clock” which switches on (or off) types of behavior in a pre-programmed way.

The classic example of the way this affects our physical development are the bodily changes that occur in early adolescence at puberty.

However, nativists also argue that maturation governs the emergence of attachment in infancy , language acquisition , and even cognitive development .

Empiricism (Extreme Nurture Position)

At the other end of the spectrum are the environmentalists – also known as empiricists (not to be confused with the other empirical/scientific  approach ).

Their basic assumption is that at birth, the human mind is a tabula rasa (a blank slate) and that this is gradually “filled” as a result of experience (e.g., behaviorism ).

From this point of view, psychological characteristics and behavioral differences that emerge through infancy and childhood are the results of learning.  It is how you are brought up (nurture) that governs the psychologically significant aspects of child development and the concept of maturation applies only to the biological.

For example, Bandura’s (1977) social learning theory states that aggression is learned from the environment through observation and imitation. This is seen in his famous bobo doll experiment (Bandura, 1961).

Also, Skinner (1957) believed that language is learned from other people via behavior-shaping techniques.

Evidence for Nature

• Biological Approach
• Biology of Gender
• Medical Model

Freud (1905) stated that events in our childhood have a great influence on our adult lives, shaping our personality.

He thought that parenting is of primary importance to a child’s development , and the family as the most important feature of nurture was a common theme throughout twentieth-century psychology (which was dominated by environmentalists’ theories).

Behavioral Genetics

Researchers in the field of behavioral genetics study variation in behavior as it is affected by genes, which are the units of heredity passed down from parents to offspring.

“We now know that DNA differences are the major systematic source of psychological differences between us. Environmental effects are important but what we have learned in recent years is that they are mostly random – unsystematic and unstable – which means that we cannot do much about them.” Plomin (2018, xii)

Behavioral genetics has enabled psychology to quantify the relative contribution of nature and nurture with regard to specific psychological traits. One way to do this is to study relatives who share the same genes (nature) but a different environment (nurture). Adoption acts as a natural experiment which allows researchers to do this.

Empirical studies have consistently shown that adoptive children show greater resemblance to their biological parents, rather than their adoptive, or environmental parents (Plomin & DeFries, 1983; 1985).

Another way of studying heredity is by comparing the behavior of twins, who can either be identical (sharing the same genes) or non-identical (sharing 50% of genes). Like adoption studies, twin studies support the first rule of behavior genetics; that psychological traits are extremely heritable, about 50% on average.

The Twins in Early Development Study (TEDS) revealed correlations between twins on a range of behavioral traits, such as personality (empathy and hyperactivity) and components of reading such as phonetics (Haworth, Davis, Plomin, 2013; Oliver & Plomin, 2007; Trouton, Spinath, & Plomin, 2002).

Implications

Jenson (1969) found that the average I.Q. scores of black Americans were significantly lower than whites he went on to argue that genetic factors were mainly responsible – even going so far as to suggest that intelligence is 80% inherited.

The storm of controversy that developed around Jenson’s claims was not mainly due to logical and empirical weaknesses in his argument. It was more to do with the social and political implications that are often drawn from research that claims to demonstrate natural inequalities between social groups.

For many environmentalists, there is a barely disguised right-wing agenda behind the work of the behavioral geneticists.  In their view, part of the difference in the I.Q. scores of different ethnic groups are due to inbuilt biases in the methods of testing.

More fundamentally, they believe that differences in intellectual ability are a product of social inequalities in access to material resources and opportunities.  To put it simply children brought up in the ghetto tend to score lower on tests because they are denied the same life chances as more privileged members of society.

Now we can see why the nature-nurture debate has become such a hotly contested issue.  What begins as an attempt to understand the causes of behavioral differences often develops into a politically motivated dispute about distributive justice and power in society.

What’s more, this doesn’t only apply to the debate over I.Q.  It is equally relevant to the psychology of sex and gender , where the question of how much of the (alleged) differences in male and female behavior is due to biology and how much to culture is just as controversial.

Polygenic Inheritance

Rather than the presence or absence of single genes being the determining factor that accounts for psychological traits, behavioral genetics has demonstrated that multiple genes – often thousands, collectively contribute to specific behaviors.

Thus, psychological traits follow a polygenic mode of inheritance (as opposed to being determined by a single gene). Depression is a good example of a polygenic trait, which is thought to be influenced by around 1000 genes (Plomin, 2018).

This means a person with a lower number of these genes (under 500) would have a lower risk of experiencing depression than someone with a higher number.

While still limited in predictive power, polygenic risk scores provide a way to quantify innate genetic risk, allowing researchers to study how this interacts with environmental factors to influence outcomes.

The high polygenicity of psychiatric disorders (many genes each contributing small effects) revealed by genetic architecture studies shows that there isn’t a simple genetic determinism for most psychiatric conditions. 

This complexity is further increased when you consider how these genes might interact with each other (epistasis) and with environmental factors. The same genetic profile might lead to different outcomes in different environments.

The Nature of Nurture

Nurture assumes that correlations between environmental factors and psychological outcomes are caused environmentally. For example, how much parents read with their children and how well children learn to read appear to be related. Other examples include environmental stress and its effect on depression.

However, behavioral genetics argues that what look like environmental effects are to a large extent really a reflection of genetic differences (Plomin & Bergeman, 1991).

People select, modify and create environments correlated with their genetic disposition. This means that what sometimes appears to be an environmental influence (nurture) is a genetic influence (nature).

So, children that are genetically predisposed to be competent readers, will be happy to listen to their parents read them stories, and be more likely to encourage this interaction.

Interaction Effects

However, in recent years there has been a growing realization that the question of “how much” behavior is due to heredity and “how much” to the environment may itself be the wrong question.

Take intelligence as an example. Like almost all types of human behavior, it is a complex, many-sided phenomenon which reveals itself (or not!) in a great variety of ways.

The “how much” question assumes that psychological traits can all be expressed numerically and that the issue can be resolved in a quantitative manner.

Heritability statistics revealed by behavioral genetic studies have been criticized as meaningless, mainly because biologists have established that genes cannot influence development independently of environmental factors; genetic and nongenetic factors always cooperate to build traits. The reality is that nature and culture interact in a host of qualitatively different ways (Gottlieb, 2007; Johnston & Edwards, 2002).

Instead of defending extreme nativist or nurturist views, most psychological researchers are now interested in investigating how nature and nurture interact.

For example, in psychopathology , this means that both a genetic predisposition and an appropriate environmental trigger are required for a mental disorder to develop. For example, epigenetics state that environmental influences affect the expression of genes.

What is Epigenetics?

Epigenetics is the term used to describe inheritance by mechanisms other than through the DNA sequence of genes. For example, features of a person’s physical and social environment can effect which genes are switched-on, or “expressed”, rather than the DNA sequence of the genes themselves.

Epigenetics refers to changes in gene expression that don’t involve alterations to the DNA sequence itself. Instead, these changes affect how genes are read and translated into proteins.

Mechanisms of Epigenetic Modification

Epigenetic modifications provide a direct biological mechanism by which environmental experiences (nurture) can alter how our genes (nature) function. This challenges the idea of genes as a fixed, unchangeable blueprint.

Epigenetic changes can occur throughout life, but certain periods (like early development or adolescence) may be particularly sensitive to these modifications.

There are several ways epigenetic changes can occur:

• DNA methylation : Adding methyl groups to DNA, typically suppressing gene expression.
• Histone modification : Changes to the proteins that DNA wraps around, affecting how tightly or loosely genes are packaged.
• Non-coding RNA : RNA molecules that can regulate gene expression.

Environmental Stressors

Environmental stressors have been shown to induce epigenetic changes, with substantial evidence from both animal and human studies (Klengel et al., 2016).

These stressors can include malnutrition, exposure to toxins, extreme stress, or trauma, leading to alterations in DNA methylation patterns, histone modifications, and changes in non-coding RNA expression (Bale, 2015).

Transgenerational Epigenetic Inheritance

Some epigenetic modifications may be passed down to future generations, suggesting that environmental influences on one generation could affect the genetic expression of subsequent generations.

One such example is what is known as the Dutch Hunger Winter, during last year of the Second World War. What they found was that children who were in the womb during the famine experienced a life-long increase in their chances of developing various health problems compared to children conceived after the famine.

Epigenetic effects can sometimes be passed from one generation to the next, although the effects only seem to last for a few generations. There is some evidence that the effects of the Dutch Hunger Winter affected grandchildren of women who were pregnant during the famine.

Therefore, it makes more sense to say that the difference between two people’s behavior is mostly due to hereditary factors or mostly due to environmental factors.

This realization is especially important given the recent advances in genetics, such as polygenic testing.  The Human Genome Project, for example, has stimulated enormous interest in tracing types of behavior to particular strands of DNA located on specific chromosomes.

If these advances are not to be abused, then there will need to be a more general understanding of the fact that biology interacts with both the cultural context and the personal choices that people make about how they want to live their lives.

There is no neat and simple way of unraveling these qualitatively different and reciprocal influences on human behavior.

The Concept of “Memories” Being Passed Down

While there’s evidence that environmental stressors can induce epigenetic changes that might affect future generations, the concept of specific “memories” being passed down is not supported by current scientific evidence.

This concept often stems from misinterpretation of studies showing behavioral or physiological changes in offspring related to parental experiences.

Some animal studies have demonstrated that offspring of stressed parents exhibit altered stress responses or behavioral changes.

For example, Dias and Ressler (2014) showed in mice that fear responses to specific odors can be passed down to subsequent generations. However, these are not “memories” in the conventional sense, but rather alterations in stress response systems or sensory sensitivities.

Human studies in this area are much more complex and limited. Research has examined children of trauma survivors (e.g., Holocaust survivors, 9/11 survivors) and found differences in stress hormone levels or risk for PTSD (Yehuda et al., 2016).

However, these studies face significant challenges in separating genetic, epigenetic, and social/cultural factors.

The challenges in interpreting human studies are substantial. Humans have complex social structures and cultural transmission of information, making it often impossible to separate the effects of biological inheritance from social learning and shared environments (Heard & Martienssen, 2014).

The longer lifespan and generation time in humans also make it challenging to study transgenerational effects. What’s often observed is not the transmission of specific memories, but rather altered predispositions or sensitivities.

For example, children of trauma survivors might have an altered stress response system, making them more sensitive to stress, but they don’t inherit specific memories of the trauma (Bowers & Yehuda, 2016).

While specific memories aren’t passed down, changes in gene expression related to stress response systems could potentially be inherited. These could affect how future generations respond to stress or process sensory information (Zannas et al., 2015).

Epigenetics: Licking Rat Pups

Michael Meaney and his colleagues at McGill University in Montreal, Canada conducted the landmark epigenetic study on mother rats licking and grooming their pups.

This research found that the amount of licking and grooming received by rat pups during their early life could alter their epigenetic marks and influence their stress responses in adulthood.

Pups that received high levels of maternal care (i.e., more licking and grooming) had a reduced stress response compared to those that received low levels of maternal care.

Meaney’s work with rat maternal behavior and its epigenetic effects has provided significant insights into the understanding of early-life experiences, gene expression, and adult behavior.

It underscores the importance of the early-life environment and its long-term impacts on an individual’s mental health and stress resilience.

Epigenetics: The Agouti Mouse Study

Waterland and Jirtle’s 2003 study on the Agouti mouse is another foundational work in the field of epigenetics that demonstrated how nutritional factors during early development can result in epigenetic changes that have long-lasting effects on phenotype.

In this study, they focused on a specific gene in mice called the Agouti viable yellow (A^vy) gene. Mice with this gene can express a range of coat colors, from yellow to mottled to brown.

This variation in coat color is related to the methylation status of the A^vy gene: higher methylation is associated with the brown coat, and lower methylation with the yellow coat.

Importantly, the coat color is also associated with health outcomes, with yellow mice being more prone to obesity, diabetes, and tumorigenesis compared to brown mice.

Waterland and Jirtle set out to investigate whether maternal diet, specifically supplementation with methyl donors like folic acid, choline, betaine, and vitamin B12, during pregnancy could influence the methylation status of the A^vy gene in offspring.

Key findings from the study include:

Dietary Influence : When pregnant mice were fed a diet supplemented with methyl donors, their offspring had an increased likelihood of having the brown coat color. This indicated that the supplemented diet led to an increased methylation of the A^vy gene.

Health Outcomes : Along with the coat color change, these mice also had reduced risks of obesity and other health issues associated with the yellow phenotype.

Transgenerational Effects : The study showed that nutritional interventions could have effects that extend beyond the individual, affecting the phenotype of the offspring.

The implications of this research are profound. It highlights how maternal nutrition during critical developmental periods can have lasting effects on offspring through epigenetic modifications, potentially affecting health outcomes much later in life.

The study also offers insights into how dietary and environmental factors might contribute to disease susceptibility in humans.

Challenges in Epigenetic Research:

• Epigenetic changes can be tissue-specific, making it challenging to study in the living human brain
• The causal direction (whether epigenetic changes cause disorders or result from them) is often unclear
• The complexity of interactions between multiple epigenetic mechanisms and genetic variants

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Further Information

• Genetic & Environmental Influences on Human Psychological Differences

Evidence for Nurture

• Classical Conditioning
• Little Albert Experiment
• Operant Conditioning
• Behaviorism
• Social Learning Theory
• Bronfenbrenner’s Ecological Systems Theory
• Social Roles
• Attachment Styles
• The Hidden Links Between Mental Disorders
• Visual Cliff Experiment
• Behavioral Genetics, Genetics, and Epigenetics
• Epigenetics
• Is Epigenetics Inherited?
• Physiological Psychology
• Bowlby’s Maternal Deprivation Hypothesis
• So is it nature not nurture after all?

Evidence for an Interaction

• Genes, Interactions, and the Development of Behavior
• Agouti Mouse Study
• Biological Psychology

What does nature refer to in the nature vs. nurture debate?

In the nature vs. nurture debate, “nature” refers to the influence of genetics, innate qualities, and biological factors on human development, behavior, and traits. It emphasizes the role of hereditary factors in shaping who we are.

What does nurture refer to in the nature vs. nurture debate?

In the nature vs. nurture debate, “nurture” refers to the influence of the environment, upbringing, experiences, and social factors on human development, behavior, and traits. It emphasizes the role of external factors in shaping who we are.

Why is it important to determine the contribution of heredity (nature) and environment (nurture) in human development?

Determining the contribution of heredity and environment in human development is crucial for understanding the complex interplay between genetic factors and environmental influences. It helps identify the relative significance of each factor, informing interventions, policies, and strategies to optimize human potential and address developmental challenges.

Nature vs. nurture: How twins can help us understand the microbiome

Apr 13, 2020 | Immunology , Microbiome

by Helen Robertson

In 1933, identical twin baby boys Oskar Stohr and Jack Yufe were separated as a consequence of their parents’ divorce. Their subsequent upbringings could not have been more different: Oskar was brought up as a Catholic in Germany and became an enthusiastic member of the Hitler Youth. Jack remained in the Caribbean where they were born, was Jewish, and even lived for a time in Israel. Yet when they were reunited some fifty years after they last saw each other they had an uncanny number of similarities. They shared thought patterns, walking gait, a taste for spicy food, and perhaps most unusually, a habit of flushing the toilet before using it.

The unfortunate separation of identical twins provides scientists with an exceptional laboratory  for exploring the “nature vs nurture” conundrum. How much of our identity is conferred by our genes, and how much is a product of the environment in which we are raised? This is also true for our microbiome: twin studies have shown that the microbiomes of identical siblings are far more similar than those of fraternal twins, indicating that genes are at play.

UChicago researchers Alexander Chervonsky, PhD, and Tatyana Golovkina, PhD , are particularly interested in exploring how genetics—especially the genes that control our immune system— influence the composition of our microbiome. They chose to explore this question with mice.

Both mice and humans have two types of immunity: innate, “inborn” immunity, the first line of defense against pathogens, and adaptive immunity, in which immune cells are trained by the specific pathogens they encounter to fight off the same bad guys in the future.

To make sure all the mice used in the study started with the same microbes, Chervonsky and Golovkina needed to isolate them from the regular, bacteria-filled world. A normal mouse—much like a normal human—is born into an environment with trillions of bacteria, spread to them from their mothers and cagemates, their handlers, bedding, and food. Fortunately, UChicago’s special germ-free “gnotobiotic” mouse facility allows scientists to experiment on mice born and raised in an environment that hosts precisely zero bacteria, which make the mice experimental blank slates.

The researchers transferred microbes from a source mouse, raised in a conventional environment, to several strains of germ-free mice: some genetically identical, others with slight differences in their immune-response genes. In collaboration with computational immunologist Aly A Khan, PhD , they compared the resulting microbiomes to see if changes to immune system genes resulted in different types of microbial communities.

They found that differences in the adaptive—targeted—immunity caused minimal differences in microbial composition, and that those differences affected only certain strains of bacteria. Other types of bacteria even took advantage of the genetic differences and multiplied.

The team was surprised to discover that it was the innate immune response—the one the mice were born with, that needs no training: it was more active in shaping the microbiome. But even then, the total influence over the microbes in the mice’s gut was fairly small, meaning there were likely other genetic and non-genetic factors at play in determining how bacteria colonized and proliferated in the animals guts.

The team intends to look deeper into understanding how genes and microbes influence each other in developing animals. But this study sets a valuable benchmark for future microbiome work: closely documenting how the immune system worked here in germ-free mice means comparisons against other studies are standardized. Now we have a better idea of the “nature” side of the equation.

The Gnotobiotic Research Animal Facility is a vital asset for researchers at UChicago, and just one example of the gold standard approaches being used by the Duchossois Family Institute to improve our understanding of the underlying components of health and wellness.

Helen Robertson is a postdoctoral scholar in Molecular Evolutionary Biology at the University of Chicago, with a keen interest in science communication and science in society.

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What Twins Can Teach Us About Nature vs. Nurture

The relative importance of nature and nurture has been debated for centuries, and has had strong — and sometimes misguided — influences on public policy.

By Jane E. Brody

The day my identical twin boys were delivered by an emergency cesarean, I noticed a behavioral difference. Twin A, who had been pushed against an unyielding pelvis for several hours, spent most of his first day alert and looking around, while Twin B, who had been spared this pre-birth stress, slept calmly like a typical newborn.

My husband and I did our best to treat them equally, but Twin A was more of a challenge to hold — we called him “our lobster baby” — while Twin B was easily cuddled. As the boys developed, we saw other differences. Twin B rehearsed all the ambulatory milestones — crawling, walking, cycling, skating, etc. — while his twin watched, then copied the skill when it was mastered.

Although they shared all their genes and grew up with the same adoring parents, clearly there were differences in these boys that had been influenced by other factors in their environment, both prenatal and postnatal.

The relative importance of nature and nurture to how a child develops has been debated by philosophers and psychologists for centuries, and has had strong — and sometimes misguided — influences on public policy.

The well-intentioned Head Start program, for example, was designed to give children from deprived environments an academic leg up. But it might have been more effective to teach their caregivers parenting and nurturing skills, as well as how to enrich the children’s environment and resist bad influences.

Children learn from what they see around them, and if what they mainly experience is violence, abuse, truancy and no expectations for success, their chances for a wholesome future are compromised from the start. As my son Erik Engquist, a fellow journalist who was Twin A, put it: “Genes define your potential, but your environment largely determines how you turn out. The few who escape negative influences are outliers.”

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Twin Study Sheds Light on Nature vs Nurture Debate

A twin study has revealed the complex interplay between genetics and environment in how our brains navigate..

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The way our brain processes different emotional and cognitive tasks may be underpinned by common factors, find scientists from UNSW and  Neuroscience Research Australia (NeuRA) .

In this latest study, recently published in the journal  Human Brain Mapping , Dr Haeme Park and Associate Professor Justine Gatt, who hold joint positions at  UNSW Psychology  and NeuRA, looked at how both emotion and cognition are influenced by the environment and genetics, using functional MRI (fMRI) scans on twins.

“There has been quite a lot of research looking at genetic versus environmental influences on brain structure,” says Dr Park, lead author of the study. “But it’s a lot harder to understand the function of our brains.”

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The results revealed that the picture is extremely complex. Some emotional and cognitive tasks were partly associated with genetics, and others exclusively with environment.

But they also found that some of the same genetic and environmental factors can play a role in the brain reacting to two different tasks. For example, the analysis showed that some of the same genetic factors are influencing how we process fear and happiness and also how we sustain our attention.

“This study is interesting because we have further insight into how much of our life experiences modulate certain brain processes, which to a certain degree we have more control over, versus your biology, which you can’t change,” says A/Prof. Gatt, Director of the  Centre for Wellbeing, Resilience and Recovery . “Knowing what areas of our brain function are linked strongly to our environment can help us develop personalised intervention approaches to promote higher mental wellbeing.” 

The importance of twin studies

The so called ‘nature vs nurture’ debate isn’t new.

In fact, twin studies have become a unique research tool used by geneticists and psychologists to evaluate the influence of genetics and the effect of a person's shared environment (family) and unique environment (the individual events that shape a life) on a particular trait.

“With twin studies, it’s important to recruit both identical and non-identical twins,” says A/Prof. Gatt. “Identical twins share 100 per cent of their genetics and if they're grown up together, they share the same environment. Whereas with the non-identical twins, they only have 50 per cent shared genetics, but they also have that common environment.”

“In this study, we wanted to bridge lots of gaps in the literature and provide a more robust and thorough picture of how our genetics and environmental factors impact the expression of brain activity during emotional and cognitive tasks, by analysing twins,” says Dr Park.

Cognitive and emotional tasks

The most recent paper is  one   of   many  from the  TWIN-E study , which recruited 1600 identical and non-identical twins from across the country in 2009 and is led by A/Prof. Gatt.

A subset of the original cohort participated in this particular study, with a total of 270 adult twins taking part.

“We get participants set up on the fMRI scanner bed which is fitted with goggles that enable them to see the tasks in front of them. The functional tasks involve them viewing different images, different stimuli, through the goggles,” says A/Prof. Gatt.

While the participants were completing the tasks, the fMRI machine was scanning their brain to measure its activity.

The twins completed a total of five tasks. Two were linked to emotional responses, such as reactions to various expressions of different faces, and the other three were associated with cognition, such as the ability to sustain attention and short-term memory.

Processing the fMRI scans show you which part of the brain light up for different processes, and how strongly the brain is activated can be measured on a scale.

“So individuals who show a lot of activation in that region have a higher number, whereas those with lower activation have a smaller number. We then use these figures to carry out what we call ‘twin modeling’ processes,” says Dr Park. “This is where we use statistics to break down how much of a role genetics and environment contributes to that number.”

Twin modelling results

Twin modelling methods revealed two key findings in their analysis of the results.

Firstly, the researchers looked at the genetic versus environmental influence on each individual task. “We know that we use different brain networks for different processes – for example, processing either a crying face or a happy face is going to use different regions in the brain compared to trying to remember someone’s phone number,” says A/Prof. Gatt. “But we found that for some of these networks, genetics plays a small to moderate, but significant role. And for other processes, it’s only the environment that determines brain function.”

The second part of the analysis found that there were similarities in the genetic and environmental factors that underpinned different tasks.

"For example, we discovered that how the brain processes fear and happiness (which was measured in the emotional tasks) and our ability to sustain attention (which was measured in the cognitive tasks), have some shared genetic factors,” says Dr Park. “This suggests that some common genetic features may underpin these very different processes.”

In contrast, the team also found that our ability to sustain our attention and our working memory have some of the same environmental contributions, suggesting that life experiences – which come from your environment – play a significant role in how brain activity is expressed for these two processes.

Mental wellbeing and resilience

While it’s clear that both our genetics and life experiences are important in determining how our brain functions, the puzzle is far from solved.

“There’s still so much more to find out!” says Dr Park. The current participants have already been followed up more recently and have performed the same tasks again after 10 years. A/Prof. Gatt, Dr Park and their team will be reassessing the results to see how the influences of genetics and environment on these brain processes change over time.

“All these results paint a complex picture of the relationship between genes and environment that give rise to the brain activity underlying our cognition and emotion,” says A/Prof. Gatt. But knowing more precise details may help to develop personalised intervention approaches in order to promote, for instance, higher mental wellbeing, or reduced psychological distress.

In fact, the ongoing TWIN-E study focuses more broadly on mental wellbeing and resilience. “So, what we're using this data for, beyond looking at genes and environment, is actually predicting mental wellbeing and resilience trajectories over time, and seeing how differences in markers like brain function and structure might profile people who are a bit more resilient or at more risk to a mental health problem,” says A/Prof. Gatt.

Understanding how much of our life experiences influences certain processes versus the influence of genetics is important when knowing what factors we can change and control, which is particularly significant for people with mood and anxiety disorders, explains A/Prof. Gatt. “If someone has a tendency to attend to negative stimuli more than positive, and we know that there's an element of environment contributing to that, with intervention or training, it’s potentially something we can target and improve for the better.”

Reference:  Park HRP, Chilver MR, Quidé Y, et al. Heritability of cognitive and emotion processing during functional MRI in a twin sample. Human Brain Mapping . 2024;45(1):e26557. doi:  10.1002/hbm.26557

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The Nature vs. Nurture Debate

Genetic and Environmental Influences and How They Interact

Verywell / Joshua Seong

• Definitions
• Interaction
• Contemporary Views

Nature refers to how genetics influence an individual's personality, whereas nurture refers to how their environment (including relationships and experiences) impacts their development. Whether nature or nurture plays a bigger role in personality and development is one of the oldest philosophical debates within the field of psychology .

Learn how each is defined, along with why the issue of nature vs. nurture continues to arise. We also share a few examples of when arguments on this topic typically occur, how the two factors interact with each other, and contemporary views that exist in the debate of nature vs. nurture as it stands today.

Nature and Nurture Defined

To better understand the nature vs. nurture argument, it helps to know what each of these terms means.

• Nature refers largely to our genetics . It includes the genes we are born with and other hereditary factors that can impact how our personality is formed and influence the way that we develop from childhood through adulthood.
• Nurture encompasses the environmental factors that impact who we are. This includes our early childhood experiences, the way we were raised , our social relationships, and the surrounding culture.

A few biologically determined characteristics include genetic diseases, eye color, hair color, and skin color. Other characteristics are tied to environmental influences, such as how a person behaves, which can be influenced by parenting styles and learned experiences.

For example, one child might learn through observation and reinforcement to say please and thank you. Another child might learn to behave aggressively by observing older children engage in violent behavior on the playground.

The Debate of Nature vs. Nurture

The nature vs. nurture debate centers on the contributions of genetics and environmental factors to human development. Some philosophers, such as Plato and Descartes, suggested that certain factors are inborn or occur naturally regardless of environmental influences.

Advocates of this point of view believe that all of our characteristics and behaviors are the result of evolution. They contend that genetic traits are handed down from parents to their children and influence the individual differences that make each person unique.

Other well-known thinkers, such as John Locke, believed in what is known as tabula rasa which suggests that the mind begins as a blank slate . According to this notion, everything that we are is determined by our experiences.

Behaviorism is a good example of a theory rooted in this belief as behaviorists feel that all actions and behaviors are the results of conditioning. Theorists such as John B. Watson believed that people could be trained to do and become anything, regardless of their genetic background.

People with extreme views are called nativists and empiricists. Nativists take the position that all or most behaviors and characteristics are the result of inheritance. Empiricists take the position that all or most behaviors and characteristics result from learning.

Examples of Nature vs. Nurture

One example of when the argument of nature vs. nurture arises is when a person achieves a high level of academic success . Did they do so because they are genetically predisposed to elevated levels of intelligence, or is their success a result of an enriched environment?

The argument of nature vs. nurture can also be made when it comes to why a person behaves in a certain way. If a man abuses his wife and kids, for instance, is it because he was born with violent tendencies, or is violence something he learned by observing others in his life when growing up?

Nature vs. Nurture in Psychology

Throughout the history of psychology , the debate of nature vs. nurture has continued to stir up controversy. Eugenics, for example, was a movement heavily influenced by the nativist approach.

Psychologist Francis Galton coined the terms 'nature versus nurture' and 'eugenics' and believed that intelligence resulted from genetics. Galton also felt that intelligent individuals should be encouraged to marry and have many children, while less intelligent individuals should be discouraged from reproducing.

The value placed on nature vs. nurture can even vary between the different branches of psychology , with some branches taking a more one-sided approach. In biopsychology , for example, researchers conduct studies exploring how neurotransmitters influence behavior, emphasizing the role of nature.

In social psychology , on the other hand, researchers might conduct studies looking at how external factors such as peer pressure and social media influence behaviors, stressing the importance of nurture. Behaviorism is another branch that focuses on the impact of the environment on behavior.

Nature vs. Nurture in Child Development

Some psychological theories of child development place more emphasis on nature and others focus more on nurture. An example of a nativist theory involving child development is Chomsky's concept of a language acquisition device (LAD). According to this theory, all children are born with an instinctive mental capacity that allows them to both learn and produce language.

An example of an empiricist child development theory is Albert Bandura's social learning theory . This theory says that people learn by observing the behavior of others. In his famous Bobo doll experiment , Bandura demonstrated that children could learn aggressive behaviors simply by observing another person acting aggressively.

Nature vs. Nurture in Personality Development

There is also some argument as to whether nature or nurture plays a bigger role in the development of one's personality. The answer to this question varies depending on which personality development theory you use.

According to behavioral theories, our personality is a result of the interactions we have with our environment, while biological theories suggest that personality is largely inherited. Then there are psychodynamic theories of personality that emphasize the impact of both.

Nature vs. Nurture in Mental Illness Development

One could argue that either nature or nurture contributes to mental health development. Some causes of mental illness fall on the nature side of the debate, including changes to or imbalances with chemicals in the brain. Genetics can also contribute to mental illness development, increasing one's risk of a certain disorder or disease.

Mental disorders with some type of genetic component include autism , attention-deficit hyperactivity disorder (ADHD), bipolar disorder , major depression , and schizophrenia .

Other explanations for mental illness are environmental. This includes being exposed to environmental toxins, such as drugs or alcohol, while still in utero. Certain life experiences can also influence mental illness development, such as witnessing a traumatic event, leading to the development of post-traumatic stress disorder (PTSD).

Nature vs. Nurture in Mental Health Therapy

Different types of mental health treatment can also rely more heavily on either nature or nurture in their treatment approach. One of the goals of many types of therapy is to uncover any life experiences that may have contributed to mental illness development (nurture).

However, genetics (nature) can play a role in treatment as well. For instance, research indicates that a person's genetic makeup can impact how their body responds to antidepressants. Taking this into consideration is important for getting that person the help they need.

Interaction Between Nature and Nurture

Which is stronger: nature or nurture? Many researchers consider the interaction between heredity and environment—nature with nurture as opposed to nature versus nurture—to be the most important influencing factor of all.

For example, perfect pitch is the ability to detect the pitch of a musical tone without any reference. Researchers have found that this ability tends to run in families and might be tied to a single gene. However, they've also discovered that possessing the gene is not enough as musical training during early childhood is needed for this inherited ability to manifest itself.

Height is another example of a trait influenced by an interaction between nature and nurture. A child might inherit the genes for height. However, if they grow up in a deprived environment where proper nourishment isn't received, they might never attain the height they could have had if they'd grown up in a healthier environment.

A newer field of study that aims to learn more about the interaction between genes and environment is epigenetics . Epigenetics seeks to explain how environment can impact the way in which genes are expressed.

Some characteristics are biologically determined, such as eye color, hair color, and skin color. Other things, like life expectancy and height, have a strong biological component but are also influenced by environmental factors and lifestyle.

Contemporary Views of Nature vs. Nurture

Most experts recognize that neither nature nor nurture is stronger than the other. Instead, both factors play a critical role in who we are and who we become. Not only that but nature and nurture interact with each other in important ways all throughout our lifespan.

As a result, many in this field are interested in seeing how genes modulate environmental influences and vice versa. At the same time, this debate of nature vs. nurture still rages on in some areas, such as in the origins of homosexuality and influences on intelligence .

While a few people take the extreme nativist or radical empiricist approach, the reality is that there is not a simple way to disentangle the multitude of forces that exist in personality and human development. Instead, these influences include genetic factors, environmental factors, and how each intermingles with the other.

Schoneberger T. Three myths from the language acquisition literature . Anal Verbal Behav . 2010;26(1):107-31. doi:10.1007/bf03393086

National Institutes of Health. Common genetic factors found in 5 mental disorders .

Pain O, Hodgson K, Trubetskoy V, et al. Identifying the common genetic basis of antidepressant response . Biol Psychiatry Global Open Sci . 2022;2(2):115-126. doi:10.1016/j.bpsgos.2021.07.008

Moulton C. Perfect pitch reconsidered . Clin Med J . 2014;14(5):517-9 doi:10.7861/clinmedicine.14-5-517

Levitt M. Perceptions of nature, nurture and behaviour . Life Sci Soc Policy . 2013;9:13. doi:10.1186/2195-7819-9-13

Bandura A, Ross D, Ross, SA. Transmission of aggression through the imitation of aggressive models . J Abnorm Soc Psychol. 1961;63(3):575-582. doi:10.1037/h0045925

Chomsky N. Aspects of the Theory of Syntax .

Galton F. Inquiries into Human Faculty and Its Development .

Watson JB. Behaviorism .

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

A new documentary chronicles the lives of triplets separated at birth in a controversial study — here's how scientists continue to use twins in research

• The documentary "Three Identical Strangers" follows the story of a secret study conducted in three genetically identical siblings who were separated at birth. 
• The study was the only twin study that followed siblings from infancy. But due to controversies over ethics, the authors never published it and the data is sealed.
• Twin experiments can give scientists insights into how different habits , treatments, or lifestyles affect two people with the same genetic makeup.
• In other twin studies, researchers have found that on average, environment and genetics have a 50/50 influence on a person's traits and disease. 
• Currently, NASA is using twins to study the effects of space on humans and mice . 

Twins have always fascinated scientists, especially as the subjects of studies about the influence of environment and genetics. 

The new documentary "Three Identical Strangers," which is now in theaters, tells the story of the ultimate test of nature versus nurture: it follows three identical brothers who were separated at birth and raised by different families. 

In 1980, two of the brothers met while attending Sullivan County Community College, and after making headlines, found the third triplet. Aside from looking alike, the three shared similar behavioral quirks and preferences.

But they were not the only twins in the study —  according to NPR , of the 13 children involved, three sets of twins and one set of triplets have discovered one another. A book titled "Identical Strangers: A Memoir of Twins Separated and Reunited" was published in 2007 by a pair of twins who were also involved, Elyse Schein and Paula Bernstein. 

The other four subjects still do not know they have identical twins. 

A controversial twin study

The study was conducted by child psychiatrist Peter Neubauer and Violet Bernard, a child psychologist. They worked with the Louise Wise Agency, which matched Jewish orphans with adoptive families, to  craft a secret experiment that would test how much of a person's behavior is genetically influenced and how much is environmentally influenced.

The researchers carefully controlled which families the identical siblings ended up in, withheld information about their biological parents, and didn't tell the adoptive families that the children were twins or had siblings. Instead, they told the families that their children were being followed for a study about the development of adopted children.

The study ultimately ended in 1980, and because of the fear of backlash and controversy over ethics and consent, Neubauer never published the results. The data is sealed in a Yale archive until 2066.

This is the only twin study that followed its subjects from infancy, but it's far from the only time scientists have used genetically identical siblings in research. 

Why scientists are obsessed with twins

The annual Twins Days Festival in Twinsburg, Ohio attracts the largest hoard of twins from all over the world. And you bet scientists are in attendance as well. 

Conducted properly, twin experiments can give scientists insights into how different habits, treatments, or lifestyles affect two people with the same genetic makeup. Studying identical twins can also help scientists pinpoint the effect of epigenetics, or environmental influences, on gene expression and function. This can help determine if certain traits or diseases lean more heavily on genetics or the environment.  

In history, twins have been used in research about I.Q., everyday diseases , eating disorders, obesity, developmental and psychological traits , and sexual orientation , according to Smithsonian Magazine . 

In a comprehensive review of twin studies worldwide, which was published in Nature Genetics in 2015, researchers  found that on average, environment and genetics have a 50/50 influence on a person's traits and disease . But certain conditions like bipolar disorder rely more heavily on genetics. 

Today, twin studies are still commonly used. There are studies on mood and anxiety disorders  as well as asthma and allergies. The Minnesota Center for Twin and Family Research  collects community-contributed data from twins that helps them map out  mental health outcomes and examine the development of substance use and related behavior disorders. For one study , they examined personality development of twins to see whether environment or genes played a role in risk-taking behaviors that lead to substance abuse. 

Most famous, however, are NASA's twin studies. After astronaut Scott Kelly got back from a year in space, scientists observed that  7% of his genes were expressed differently than those of his identical twin .  The genes that were altered were related to the immune system, bone formation, DNA repair, and responses to an oxygen-depleted or carbon-dioxide rich environment. 

On top of this, Scott Kelly's telomeres — the caps at the ends of our chromosomes that affects cell aging — appeared to get longer in space, but they shrunk back when he returned to Earth. His gut also hosted different bacteria, and he returned two inches taller.

NASA recently sent 20 mice into space while their twins stay on Earth. In partnership with astronauts on the International Space Station, agency scientists plan to study changes in the rodents' microbiomes and circadian cycles. 

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Hidden Brain

What twins can tell us about who we are.

Shankar Vedantam

Laura Kwerel

What Twins Tell Us

In March of 2017, the two sets of Bogotá twins, Jorge, William, Carlos and Wilber (left to right), gathered to celebrate Carlos's graduation. Diana Carolina/St. Martin's Press hide caption

In March of 2017, the two sets of Bogotá twins, Jorge, William, Carlos and Wilber (left to right), gathered to celebrate Carlos's graduation.

In December 1988, two sets of identical twins in Bogotá became test subjects in a study for which they had never volunteered. It was an experiment that could never be performed in a lab, and had never before been documented. And it became a testament to the eternal tug between nature and nurture in shaping who we are.

The brothers as children. From left to right: Carlos and Jorge at age 5, and Wilber and William at age 6. Courtesy of Jorge and Carlos; William and Wilber/St. Martin's Press hide caption

The brothers as children. From left to right: Carlos and Jorge at age 5, and Wilber and William at age 6.

This week, psychologist Nancy Segal tells the story of the Bogotá twins, which was a tragedy, a soap opera, and a science experiment, all rolled into one. And she explains why twin studies aren't just for twins. They can serve as a paradigm to understand age-old questions that affect us all: Is our fate written in our genes? And how powerful is upbringing in shaping who we become?

Insights — and provocations — from twin studies, this week on Hidden Brain .

Additional Resources:

" Accidental Brothers: The Story of Twins Exchanged at Birth and the Power of Nature and Nurture ," by Nancy Segal and Yesika Montoya, 2018

"Born Together—Reared Apart: The Landmark Minnesota Twin Study," by Nancy Segal, 2012

" Pairs of Genetically Unrelated Look-Alikes: Further Tests of Personality Similarity and Social Affiliation," by Nancy Segal and colleagues, 2018

"Socioeconomic Status Modifies Heritability of IQ in Young Children," by Eric Turkheimer and colleagues, 2003

" Personality Similarity in Twins Reared Apart and Together," by Thomas Bouchard and colleagues, 1988

Hidden Brain is hosted by Shankar Vedantam and produced by Jennifer Schmidt, Parth Shah, Rhaina Cohen, Laura Kwerel, and Thomas Lu. Our supervising producer is Tara Boyle. You can also follow us on Twitter @hiddenbrain , and listen for Hidden Brain stories each week on your local public radio station.

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What Are Nature vs. Nurture Examples?

How is nature defined, how is nurture defined, the nature vs. nurture debate, nature vs. nurture examples, what is empiricism (extreme nurture position), contemporary views of nature vs. nurture.

Nature vs. nurture is an age-old debate about whether genetics (nature) plays a bigger role in determining a person's characteristics than lived experience and environmental factors (nurture). The term "nature vs. nature" was coined by English naturalist Charles Darwin's younger half-cousin, anthropologist Francis Galton, around 1875.

In psychology, the extreme nature position (nativism) proposes that intelligence and personality traits are inherited and determined only by genetics.

On the opposite end of the spectrum, the extreme nurture position (empiricism) asserts that the mind is a blank slate at birth; external factors like education and upbringing determine who someone becomes in adulthood and how their mind works. Both of these extreme positions have shortcomings and are antiquated.

This article explores the difference between nature and nurture. It gives nature vs. nurture examples and explains why outdated views of nativism and empiricism don't jibe with contemporary views. 

Thanasis Zovoilis / Getty Images

In the context of nature vs. nurture, "nature" refers to genetics and heritable factors that are passed down to children from their biological parents.

Genes and hereditary factors determine many aspects of someone’s physical appearance and other individual characteristics, such as a genetically inherited predisposition for certain personality traits.

Scientists estimate that 20% to 60% percent of temperament is determined by genetics and that many (possibly thousands) of common gene variations combine to influence individual characteristics of temperament.

However, the impact of gene-environment (or nature-nurture) interactions on someone's traits is interwoven. Environmental factors also play a role in temperament by influencing gene activity. For example, in children raised in an adverse environment (such as child abuse or violence), genes that increase the risk of impulsive temperamental characteristics may be activated (turned on).

Trying to measure "nature vs. nurture" scientifically is challenging. It's impossible to know precisely where the influence of genes and environment begin or end.

How Are Inherited Traits Measured?

“Heritability”   describes the influence that genes have on human characteristics and traits. It's measured on a scale of 0.0 to 1.0. Very strong heritable traits like someone's eye color are ranked a 1.0.

Traits that have nothing to do with genetics, like speaking with a regional accent ranks a zero. Most human characteristics score between a 0.30 and 0.60 on the heritability scale, which reflects a blend of genetics (nature) and environmental (nurture) factors.

Thousands of years ago, ancient Greek philosophers like Plato believed that "innate knowledge" is present in our minds at birth. Every parent knows that babies are born with innate characteristics. Anecdotally, it may seem like a kid's "Big 5" personality traits (agreeableness, conscientiousness, extraversion, neuroticism, and openness) were predetermined before birth.

What is the "Big 5" personality traits

The Big 5 personality traits is a theory that describes the five basic dimensions of personality. It was developed in 1949 by D. W. Fiske and later expanded upon by other researchers and is used as a framework to study people's behavior.

From a "nature" perspective, the fact that every child has innate traits at birth supports Plato's philosophical ideas about innatism. However, personality isn't set in stone. Environmental "nurture" factors can change someone's predominant personality traits over time. For example, exposure to the chemical lead during childhood may alter personality.

In 2014, a meta-analysis of genetic and environmental influences on personality development across the human lifespan found that people change with age. Personality traits are relatively stable during early childhood but often change dramatically during adolescence and young adulthood.

It's impossible to know exactly how much "nurture" changes personality as people get older. In 2019, a study of how stable personality traits are from age 16 to 66 found that people's Big 5 traits are both stable and malleable (able to be molded). During the 50-year span from high school to retirement, some traits like agreeableness and conscientiousness tend to increase, while others appear to be set in stone.

Nurture refers to all of the external or environmental factors that affect human development such as how someone is raised, socioeconomic status, early childhood experiences, education, and daily habits.

Although the word "nurture" may conjure up images of babies and young children being cared for by loving parents, environmental factors and life experiences have an impact on our psychological and physical well-being across the human life span. In adulthood, "nurturing" oneself by making healthy lifestyle choices can offset certain genetic predispositions.

For example, a May 2022 study found that people with a high genetic risk of developing the brain disorder Alzheimer's disease can lower their odds of developing dementia (a group of symptoms that affect memory, thinking, and social abilities enough to affect daily life) by adopting these seven healthy habits in midlife:

• Staying active
• Healthy eating
• Losing weight
• Not smoking
• Reducing blood sugar
• Controlling cholesterol
• Maintaining healthy blood pressure

The nature vs. nurture debate centers around whether individual differences in behavioral traits and personality are caused primarily by nature or nurture. Early philosophers believed the genetic traits passed from parents to their children influence individual differences and traits. Other well-known philosophers believed the mind begins as a blank slate and that everything we are is determined by our experiences.

While early theories favored one factor over the other, experts today recognize there is a complex interaction between genetics and the environment and that both nature and nurture play a critical role in shaping who we are.

Eye color and skin pigmentation are examples of "nature" because they are present at birth and determined by inherited genes. Developmental delays due to toxins (such as exposure to lead as a child or exposure to drugs in utero) are examples of "nurture" because the environment can negatively impact learning and intelligence.

In Child Development

The nature vs. nurture debate in child development is apparent when studying language development. Nature theorists believe genetics plays a significant role in language development and that children are born with an instinctive ability that allows them to both learn and produce language.

Nurture theorists would argue that language develops by listening and imitating adults and other children.

In addition, nurture theorists believe people learn by observing the behavior of others. For example, contemporary psychologist Albert Bandura's social learning theory suggests that aggression is learned through observation and imitation.

In Psychology

In psychology, the nature vs. nurture beliefs vary depending on the branch of psychology.

• Biopsychology:  Researchers analyze how the brain, neurotransmitters, and other aspects of our biology influence our behaviors, thoughts, and feelings. emphasizing the role of nature.
• Social psychology: Researchers study how external factors such as peer pressure and social media influence behaviors, emphasizing the importance of nurture.
• Behaviorism: This theory of learning is based on the idea that our actions are shaped by our interactions with our environment.

In Personality Development

Whether nature or nurture plays a bigger role in personality development depends on different personality development theories.

• Behavioral theories: Our personality is a result of the interactions we have with our environment, such as parenting styles, cultural influences, and life experiences.
• Biological theories: Personality is mostly inherited which is demonstrated by a study in the 1990s that concluded identical twins reared apart tend to have more similar personalities than fraternal twins.
• Psychodynamic theories: Personality development involves both genetic predispositions and environmental factors and their interaction is complex.

In Mental Illness

Both nature and nurture can contribute to mental illness development.

For example, at least five mental health disorders are associated with some type of genetic component ( autism ,  attention-deficit hyperactivity disorder (ADHD) ,  bipolar disorder , major depression, and  schizophrenia ).

Other explanations for mental illness are environmental, such as:

• Being exposed to drugs or alcohol in utero 
• Witnessing a traumatic event, leading to post-traumatic stress disorder (PTSD)
• Adverse life events and chronic stress during childhood

In Mental Health Therapy

Mental health treatment can involve both nature and nurture. For example, a therapist may explore life experiences that may have contributed to mental illness development (nurture) as well as family history of mental illness (nature).

At the same time, research indicates that a person's genetic makeup may impact how their body responds to antidepressants. Taking this into consideration is important for finding the right treatment for each individual.

 What Is Nativism (Extreme Nature Position)?

Innatism emphasizes nature's role in shaping our minds and personality traits before birth. Nativism takes this one step further and proposes that all of people's mental and physical characteristics are inherited and predetermined at birth.

In its extreme form, concepts of nativism gave way to the early 20th century's racially-biased eugenics movement. Thankfully, "selective breeding," which is the idea that only certain people should reproduce in order to create chosen characteristics in offspring, and eugenics, arranged breeding, lost momentum during World War II. At that time, the Nazis' ethnic cleansing (killing people based on their ethnic or religious associations) atrocities were exposed.

Philosopher John Locke's tabula rasa theory from 1689 directly opposes the idea that we are born with innate knowledge. "Tabula rasa" means "blank slate" and implies that our minds do not have innate knowledge at birth.

Locke was an empiricist who believed that all the knowledge we gain in life comes from sensory experiences (using their senses to understand the world), education, and day-to-day encounters after being born.

Today, looking at nature vs. nature in black-and-white terms is considered a misguided dichotomy (two-part system). There are so many shades of gray where nature and nurture overlap. It's impossible to tease out how inherited traits and learned behaviors shape someone's unique characteristics or influence how their mind works.

The influences of nature and nurture in psychology are impossible to unravel. For example, imagine someone growing up in a household with an alcoholic parent who has frequent rage attacks. If that child goes on to develop a substance use disorder and has trouble with emotion regulation in adulthood, it's impossible to know precisely how much genetics (nature) or adverse childhood experiences (nurture) affected that individual's personality traits or issues with alcoholism.

Epigenetics Blurs the Line Between Nature and Nurture

"Epigenetics " means "on top of" genetics. It refers to external factors and experiences that turn genes "on" or "off." Epigenetic mechanisms alter DNA's physical structure in utero (in the womb) and across the human lifespan.

Epigenetics blurs the line between nature and nurture because it says that even after birth, our genetic material isn't set in stone; environmental factors can modify genes during one's lifetime. For example, cannabis exposure during critical windows of development can increase someone's risk of neuropsychiatric disease via epigenetic mechanisms.

Nature vs. nurture is a framework used to examine how genetics (nature) and environmental factors (nurture) influence human development and personality traits.

However, nature vs. nurture isn't a black-and-white issue; there are many shades of gray where the influence of nature and nurture overlap. It's impossible to disentangle how nature and nurture overlap; they are inextricably intertwined. In most cases, nature and nurture combine to make us who we are. 

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By Christopher Bergland Bergland is a retired ultra-endurance athlete turned medical writer and science reporter. He is based in Massachusetts.

Twins Separated at Birth Reveal Staggering Influence of Genetics

WASHINGTON — Jim Lewis and Jim Springer were identical twins raised apart from the age of 4 weeks. When the twins were finally reunited at the age of 39 in 1979, they discovered they both suffered from tension headaches, were prone to nail biting, smoked Salem cigarettes, drove the same type of car and even vacationed at the same beach in Florida.

The culprit for the odd similarities? Genes.

Genes can help explain why someone is gay or straight, religious or not, brainy or not, and even whether they're likely to develop gum disease, one psychologist explains.

Such broad-ranging genetic effects first came to light in a landmark study — Minnesota Twin Family Study — conducted from 1979 to 1999, which followed identical and fraternal twins who were separated at an early age. [ Seeing Double: 8 Fascinating Facts About Twins ]

"We were surprised by certain behaviors that showed a genetic influence, such as religiosity [and] social attitudes," said Nancy Segal, an evolutionary psychologist at California State University, Fullerton, who was part of the study for nine years. "Those surprised us, because we thought those certainly must come from the family [environment]," Segal told Live Science. Segal described the groundbreaking research on Aug. 7 here at a meeting of the American Psychological Association.

Born together, raised apart

Researchers at the University of Minnesota, led by Thomas Bouchard, launched the landmark study in 1979. Over the course of 20 years, they studied 137 pairs of twins — 81 pairs of identical twins (twins who developed from one egg that split in two), and 56 pairs of fraternal twins (twins who developed from two eggs fertilized by two different sperm).

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The Jim twins were probably the most famous set of twins involved in the study, but other pairs were equally fascinating. One pair of female twins in the study were separated from each other at 5 months old, and weren't reunited until age 78, making them the world's longest separated pair in Guinness World Records .

The Minnesota study resulted in more than 170 individual studies focusing on different medical and psychological characteristics.

In one study, the researchers took photographs of the twins, and found that identical twins would stand the same way, while fraternal twins had different postures.

Another study of four pairs of twins found that genetics had a stronger influence on sexual orientation in male twins than in female twins. A recent study in Sweden of 4,000 pairs of twins has replicated these findings, Segal said. [ 5 Myths About Gay People Debunked ]

Nature vs. nurture

A 1986 study that was part of the larger Minnesota study found that genetics plays a larger role on personality than previously thought. Environment affected personality when twins were raised apart, but not when they were raised together, the study suggested.

Reporter Daniel Goleman wrote in The New York Times at the time that genetic makeup was more influential on personality than child rearing — a finding he said would launch "fierce debate."

"We never said [family environment] didn't matter," Segal said at the APA meeting. "We just made the point that environment works in ways we hadn't expected."

Another study, commissioned by the editor of the journal Science, looked at genetics and IQ. The Minnesota researchers found that about 70 percent of IQ variation across the twin population was due to genetic differences among people, and 30 percent was due to environmental differences. The finding received both praise and criticism, but an updated study in 2009 containing new sets of twins found a similar correlation between genetics and IQ .

Moreover, a study in 1990 found that genetics account for 50 percent of the religiosity among the population — in other words, both identical twins raised apart were more likely to be religious or to be not religious, compared with unrelated individuals.

Other studies found a strong genetic influence on dental or gum health. That research helped to show that gum disease isn't just caused by bacteria, it also has a genetic component, Segal said.

Another study found that happiness and well-being had a 50 percent genetic influence.

In another study, researchers surveyed the separated twins about how close they felt to their newfound sibling. Among identical twins, 80 percent of those surveyed reported feeling closer and more familiar with their twin than they did to their best friends, suggesting a strong genetic component in the bond between identical twins.

— 7 diseases you can learn about from a genetic test

— Genetics by the numbers: 10 tantalizing tales

— If identical twins married identical twins, how genetically similar would their children be?  

The Minnesota study gave scientists a new understanding of the role of genes and environment on human development, Segal said. In the future, twin studies will aim to link specific genes to specific behaviors, as well as investigate epigenetics — what turns genes on or off, she said.

Segal, who wrote a book about the study called "Born Together — Reared Apart: The Landmark Minnesota Twins Study" (Harvard University Press, 2012), is now doing a prospective study of Chinese twins raised apart, often in different countries, by adoptive families.

Originally published on Live Science.

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Epigenetics and Child Development: How Children’s Experiences Affect Their Genes

For more information about epigenetics, please scroll down below the infographic .

New scientific research shows that environmental influences can actually affect whether and how genes are expressed. In fact, scientists have discovered that early experiences can determine how genes are turned on and off and even whether some are expressed at all. Thus, the old ideas that genes are “set in stone” or that they alone determine development have been disproven. Nature vs. Nurture is no longer a debate—it’s nearly always both!

More Information on Epigenetics Deep Dive: Gene-Environment Interaction Learn more about the physical and chemical processes that take place as part of the creation of the epigenome. Working Paper 10: Early Experiences Can Alter Gene Expression and Affect Long-Term Development This in-depth working paper explains how genes and the environment interact, and gives recommendations for ways that caregivers and policymakers can effectively respond to the science.

During development, the DNA that makes up our genes accumulates chemical marks that determine how much or little of the genes is expressed. This collection of chemical marks is known as the “ epigenome .” The different experiences children have rearrange those chemical marks. This explains why genetically identical twins can exhibit different behaviors, skills, health, and achievement.

Correcting Popular Misrepresentations of Science

Until recently, the influences of genes were thought to be set, and the effects of children’s experiences and environments on brain architecture and long-term physical and mental health outcomes remained a mystery. That lack of understanding led to several misleading conclusions about the degree to which negative and positive environmental factors and experiences can affect the developing fetus and young child. The following misconceptions are particularly important to set straight.

• Contrary to popular belief, the genes inherited from one’s parents do not set a child’s future development in stone. Variations in DNA sequences between individuals certainly influence the way in which genes are expressed and how the proteins encoded by those genes will function. But that is only part of the story—the environment in which one develops , before and soon after birth, provides powerful experiences that chemically modify certain genes which, in turn, define how much and when they are expressed. Thus, while genetic factors exert potent influences, environmental factors have the ability to alter the genes that were inherited.
• Although frequently misunderstood, adverse fetal and early childhood experiences can—and do—lead to physical and chemical changes in the brain that can last a lifetime. Injurious experiences , such as malnutrition, exposure to chemical toxins or drugs, and toxic stress before birth or in early childhood are not “forgotten,” but rather are built into the architecture of the developing brain through the epigenome. The “biological memories” associated with these epigenetic changes can affect multiple organ systems and increase the risk not only for poor physical and mental health outcomes but also for impairments in future learning capacity and behavior.
• Despite some marketing claims to the contrary, the ability of so-called enrichment programs to enhance otherwise healthy brain development is not known. While parents and policymakers might hope that playing Mozart recordings to newborns will produce epigenetic changes that enhance cognitive development, there is absolutely no scientific evidence that such exposure will shape the epigenome or enhance brain function. What research has shown is that specific epigenetic modifications do occur in brain cells as cognitive skills like learning and memory develop, and that repeated activation of brain circuits dedicated to learning and memory through interaction with the environment, such as reciprocal “ serve and return ” interaction with adults, facilitates these positive epigenetic modifications. We also know that sound maternal and fetal nutrition , combined with positive social-emotional support of children through their family and community environments, will reduce the likelihood of negative epigenetic modifications that increase the risk of later physical and mental health impairments.

The epigenome can be affected by positive experiences, such as supportive relationships and opportunities for learning, or negative influences, such as environmental toxins or stressful life circumstances, which leave a unique epigenetic “signature” on the genes. These signatures can be temporary or permanent and both types affect how easily the genes are switched on or off. Recent research demonstrates that there may be ways to reverse certain negative changes and restore healthy functioning, but that takes a lot more effort, may not be successful at changing all aspects of the signatures, and is costly. Thus, the very best strategy is to support responsive relationships and reduce stress to build strong brains from the beginning, helping children grow up to be healthy, productive members of society.

For more information:   Early Experiences Can Alter Gene Expression and Affect Long-Term Development: Working Paper No. 10 .

Full Text of the Graphic

“Epigenetics” is an emerging area of scientific research that shows how environmental influences—children’s experiences—actually affect the expression of their genes.

This means the old idea that genes are “set in stone” has been disproven. Nature vs. Nurture is no longer a debate. It’s nearly always both!

During development, the DNA that makes up our genes accumulates chemical marks that determine how much or little of the genes is expressed. This collection of chemical marks is known as the “epigenome.” The different experiences children have rearrange those chemical marks. This explains why genetically identical twins can exhibit different behaviors, skills, health, and achievement.

Epigenetics explains how early experiences can have lifelong impacts.

The genes children inherit from their biological parents provide information that guides their development. For example, how tall they could eventually become or the kind of temperament they could have.

When experiences during development rearrange the epigenetic marks that govern gene expression, they can change whether and how genes release the information they carry.

Thus, the epigenome can be affected by positive experiences, such as supportive relationships and opportunities for learning, or negative influences, such as environmental toxins or stressful life circumstances, which leave a unique epigenetic “signature” on the genes. These signatures can be temporary or permanent and both types affect how easily the genes are switched on or off. Recent research demonstrates that there may be ways to reverse certain negative changes and restore healthy functioning. But the very best strategy is to support responsive relationships and reduce stress to build strong brains from the beginning.

Young brains are particularly sensitive to epigenetic changes.

Experiences very early in life, when the brain is developing most rapidly, cause epigenetic adaptations that influence whether, when, and how genes release their instructions for building future capacity for health, skills, and resilience. That’s why it’s crucial to provide supportive and nurturing experiences for young children in the earliest years.

Services such as high-quality health care for all pregnant women, infants, and toddlers, as well as support for new parents and caregivers can—quite literally— affect the chemistry around children’s genes. Supportive relationships and rich learning experiences generate positive epigenetic signatures that activate genetic potential.

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Article contents

Nature and nurture as an enduring tension in the history of psychology.

• Hunter Honeycutt Hunter Honeycutt Bridgewater College, Department of Psychology
• https://doi.org/10.1093/acrefore/9780190236557.013.518
• Published online: 30 September 2019

Nature–nurture is a dichotomous way of thinking about the origins of human (and animal) behavior and development, where “nature” refers to native, inborn, causal factors that function independently of, or prior to, the experiences (“nurture”) of the organism. In psychology during the 19th century, nature-nurture debates were voiced in the language of instinct versus learning. In the first decades of the 20th century, it was widely assumed that that humans and animals entered the world with a fixed set of inborn instincts. But in the 1920s and again in the 1950s, the validity of instinct as a scientific construct was challenged on conceptual and empirical grounds. As a result, most psychologists abandoned using the term instinct but they did not abandon the validity of distinguishing between nature versus nurture. In place of instinct, many psychologists made a semantic shift to using terms like innate knowledge, biological maturation, and/or hereditary/genetic effects on development, all of which extend well into the 21st century. Still, for some psychologists, the earlier critiques of the instinct concept remain just as relevant to these more modern usages.

The tension in nature-nurture debates is commonly eased by claiming that explanations of behavior must involve reference to both nature-based and nurture-based causes. However, for some psychologists there is a growing pressure to see the nature–nurture dichotomy as oversimplifying the development of behavior patterns. The division is seen as both arbitrary and counterproductive. Rather than treat nature and nurture as separable causal factors operating on development, they treat nature-nurture as a distinction between product (nature) versus process (nurture). Thus there has been a longstanding tension about how to define, separate, and balance the effects of nature and nurture.

• nature–nurture
• development
• nativism–empiricism
• innate–learned
• behavioral genetics
• epigenetics

Nature and Nurture in Development

The oldest and most persistent ways to frame explanations about the behavioral and mental development of individuals is to distinguish between two separate sources of developmental causation: (a) intrinsic, preformed, or predetermined causes (“nature”) versus (b) extrinsic, experiential, or environmental causes (“nurture”). Inputs from these two sources are thought to add their own contribution to development (see Figure 1 ).

Figure 1. The traditional view of nature and nurture as separate causes of development. In the traditional view, nature and nurture are treated as independent causal influences that combine during development to generate outcomes. Note that, during development, the effects of nature and nurture (shown in horizontal crossing lines) remain independent so that their effects on outcomes are theoretically separable.

Because some traits seem to derive more from one source than the other, much of the tension associated with the nature–nurture division deals with disagreements about how to balance the roles of nature and nurture in the development of a trait.

Evidence of Nature in Development

Evidence to support the nature–nurture division usually derives from patterns of behavior that suggest a limited role of environmental causation, thus implying some effect of nature by default. Table 1 depicts some common descriptors and conditions used to infer that some preference, knowledge, or skill is nature based.

Table 1. Common Descriptors and Associated Conditions for Inferring the Effects of Nature on Development

It is important to reiterate that nature-based causation (e.g., genetic determination) is inferred from these observations. Such inferences can generate tension because each of the observations listed here can be explained by nurture-based (environmental) factors. Confusion can also arise when evidence of one descriptor (e.g., being hereditary) is erroneously used to justify a different usage (e.g., that the trait is unlearned).

The Origins of Nature Versus Nurture

For much of recorded history, the distinction between nature and nurture was a temporal divide between what a person is innately endowed with at birth, prior to experience (nature), and what happens thereafter (nurture). It was not until the 19th century that the temporal division was transformed into a material division of causal influences (Keller, 2010 ). New views about heredity and Darwinian evolution justified distinguishing between native traits and genetic causes from acquired traits and environmental causes. More so than before, the terms nature and nurture were often juxtaposed in an opposition famously described by Sir Francis Galton ( 1869 ) as that between “nature versus nurture.”

Galton began writing about heredity in the mid-1860s. He believed we would discover laws governing the transmission of mental as well as physical qualities. Galton’s take on mental heredity, however, was forged by his desire to improve the human race in a science he would later call “eugenics.” In the mid- 19th century , British liberals assumed humans were equivalent at birth. Their social reform efforts were geared to enhancing educational opportunities and improving living conditions. Galton, a political conservative, opposed the notion of natural equality, arguing instead that people were inherently different at birth (Cowan, 2016 ), and that these inherited mental and behavioral inequalities were transmitted through lineages like physical qualities. Because Galton opposed the widely held Lamarckian idea that the qualities acquired in one’s lifetime could modify the inherited potential of subsequent generations, he believed long-lasting improvement of the human stock would only come by controlling breeding practices.

To explain the biological mechanisms of inheritance, Galton joined a growing trend in the 1870s to understand inheritance as involving the transmission of (hypothetical) determinative, germinal substances across generations. Foreshadowing a view that would later become scientific orthodoxy, Galton believed these germinal substances to be uninfluenced by the experiences of the organism. His theory of inheritance, however, was speculative. Realizing he was not equipped to fully explicate his theory of biological inheritance, Galton abandoned this line of inquiry by the end of that decade and refocused his efforts on identifying statistical laws of heredity of individual differences (Renwick, 2011 ).

Historians generally agree that Galton was the first to treat nature (as heredity) and nurture (everything else) as separate causal forces (Keller, 2010 ), but the schism gained biological legitimacy through the work of the German cytologist Auguste Weismann in the 1880s. Whereas Galton’s theory was motivated by his political agenda, Weismann was motivated by a scientific, theoretical agenda. Namely, Weismann opposed Lamarckian inheritance and promoted a view of evolution driven almost entirely by natural selection.

Drawing upon contemporary cytological and embryological research, Weismann made the case that the determinative substances found in the germ cells of plants and animals (called the “germ-plasm”) that are transmitted across generations were physically sequestered very early in embryogenesis and remained buffered from the other cells of the body (“somato-plasm”). This so-called, Weismann’s barrier meant that alterations in the soma that develop in the lifetime of the organism through the use or disuse of body parts would not affect the germinal substances transmitted during reproduction (see Winther, 2001 , for review). On this view, Lamarckian-style inheritance of acquired characteristics was not biologically possible.

Galton and Weismann’s influence on the life sciences cannot be overstated. Their work convinced many to draw unusually sharp distinctions between the inherited (nature) and the acquired (nurture). Although their theories were met with much resistance and generated significant tension in the life sciences from cytology to psychology, their efforts helped stage a new epistemic space through which to appreciate Mendel’s soon to be rediscovered breeding studies and usher in genetics (Muller-Wille & Rheinberger, 2012 ).

Ever since, psychology has teetered between nature-biased and nurture-biased positions. With the rise of genetics, the wedge between nature–nurture was deepened in the early to mid- 20th century , creating fields of study that focused exclusively on the effects of either nature or nurture.

The “Middle Ground” Perspective on Nature–Nurture

Twenty-first-century psychology textbooks often state that the nature–nurture debates have been resolved, and the tension relaxed, because we have moved on from emphasizing nature or nurture to appreciating that development necessarily involves both nature and nurture. In this middle-ground position, one asks how nature and nurture interact. For example, how do biological (or genetic) predispositions for behaviors or innate knowledge bias early learning experiences? Or how might environmental factors influence the biologically determined (maturational) unfolding of bodily form and behaviors?

Rejection of the Nature–Nurture Divide

For some, the “middle-ground” resolution is as problematic as “either/or” views and does not resolve a deeper source of tension inherent in the dichotomy. On this view, the nature–nurture divide is neither a legitimate nor a constructive way of thinking about development. Instead, developmental analysis reveals that the terms commonly associated with nature (e.g., innate, genetic, hereditary, or instinctual) and nurture (environmental or learned) are so entwined and confounded (and often arbitrary) that their independent effects cannot be meaningfully discussed. The nature–nurture division oversimplifies developmental processes, takes too much for granted, and ultimately hinders scientific progress. Thus not only is there a lingering tension about how to balance the effects of nature and nurture in the middle-ground view, but there is also a growing tension to move beyond the dichotomous nature–nurture framework.

Nativism in Behavior: Instincts

Definitions of instinct can vary tremendously, but many contrast (a) instinct with reason (or intellect, thought, will), which is related to but separable from contrasting (b) instinct with learning (or experience or habit).

Instinct in the Age of Enlightenment

Early usages of the instinct concept, following Aristotle, treated instinct as a mental, estimative faculty ( vis aestimativa or aestimativa naturalis ) in humans and animals that allowed for the judgments of objects in the world (e.g., seeing a predator) to be deemed beneficial or harmful in a way that transcends immediate sensory experience but does not involve the use of reason (Diamond, 1971 ). In many of the early usages, the “natural instinct” of animals even included subrational forms of learning.

The modern usage of instincts as unlearned behaviors took shape in the 17th century . By that point it was widely believed that nature or God had implanted in animals and humans innate behaviors and predispositions (“instincts”) to promote the survival of the individual and the propagation of the species. Disagreements arose as to whether instincts derived from innate mental images or were mindlessly and mechanically (physiologically) generated from innately specified bodily organization (Richards, 1987 ).

Anti-Instinct Movement in the Age of Enlightenment

Challenges to the instinct concept can be found in the 16th century (see Diamond, 1971 ), but they were most fully developed by empiricist philosophers of the French Sensationalist tradition in the 18th century (Richards, 1987 ). Sensationalists asserted that animals behaved rationally and all of the so-called instincts displayed by animals could be seen as intelligently acquired habits.

For Sensationalists, instincts, as traditionally understood, did not exist. Species-specificity in behavior patterns could be explained by commonalities in physiological organization, needs, and environmental conditions. Even those instinctual behaviors seen at birth (e.g., that newly hatched chicks peck and eat grain) might eventually be explained by the animal’s prenatal experiences. Erasmus Darwin ( 1731–1802 ), for example, speculated that the movements and swallowing experiences in ovo could account for the pecking and eating of grain by young chicks. The anti-instinct sentiment was clearly expressed by the Sensationalist Jean Antoine Guer ( 1713–1764 ), who warned that instinct was an “infantile idea” that could only be held by those who are ignorant of philosophy, that traditional appeals to instincts in animals not only explained nothing but served to hinder scientific explanations, and that nothing could be more superficial than to explain behavior than appealing to so-called instincts (Richards, 1987 ).

The traditional instinct concept survived. For most people, the complex, adaptive, species-specific behaviors displayed by naïve animals (e.g., caterpillars building cocoons; infant suckling behaviors) appeared to be predetermined and unlearned. Arguably as important, however, was the resistance to the theological implications of Sensationalist philosophy.

One of the strongest reactions to Sensationalism was put forward in Germany by Herman Samuel Reimarus ( 1694–1768 ). As a natural theologian, Reimarus, sought evidence of a God in the natural world, and the species-specific, complex, and adaptive instincts of animals seemed to stand as the best evidence of God’s work. More so than any other, Reimarus extensively catalogued instincts in humans and animals. Rather than treat instincts as behaviors, he defined instincts as natural impulses (inner drives) to act that were expressed perfectly, without reflection or practice, and served adaptive goals (Richards, 1987 ). He even proposed instincts for learning, a proposal that would resurface in the mid- 20th century , as would his drive theory of instinct (Jaynes & Woodward, 1974 ).

Partly as a result of Reimarus’ efforts, the instinct concept survived going into the 19th century . But many issues surrounding the instinct concept were left unsettled. How do instincts differ from reflexive behaviors? What role does learning play in the expression of instincts, if any? Do humans have more or fewer instincts than animals? These questions would persist well into the first decades of the 20th century and ultimately fuel another anti-instinct movement.

Instinct in the 19th Century

In the 19th century , the tension about the nature and nurture of instincts in the lifetime of animals led to debates about the nature and nurture of instincts across generations . These debates dealt with whether instincts should be viewed as “inherited habits” from previous generations or whether they result from the natural selection. Debating the relative roles of neo-Lamarckian use-inheritance versus neo-Darwinian natural selection in the transmutation of species became a significant source of tension in the latter half of the 19th century . Although the neo-Lamarckian notion of instincts as being inherited habits was rejected in the 20th century , it has resurged in recent years (e.g., see Robinson & Barron, 2017 ).

Darwinian evolutionary theory required drawing distinctions between native and acquired behaviors, and, perhaps more so than before, behaviors were categorized along a continuum from the purely instinctive (unlearned), to the partially instinctive (requiring some learning), to the purely learned. Still, it was widely assumed that a purely instinctive response would be modified by experience after its first occurrence. As a result, instinct and habit were very much entangled in the lifetime of the organism. The notion of instincts as fixed and unmodifiable would not be widely advanced until after the rise of Weismann’s germ-plasm theory in the late 19thcentury .

Given their importance in evolutionary theory, there was greater interest in more objectively identifying pure instincts beyond anecdotal reports. Some of the most compelling evidence was reported by Douglas Spalding ( 1844–1877 ) in the early 1870s (see Gray, 1967 ). Spalding documented numerous instances of how naïve animals showed coordinated, seemingly adaptive responses (e.g., hiding) to objects (e.g., sight of predators) upon their first encounter, and he helped pioneer the use of the deprivation experiment to identify instinctive behaviors. This technique involved selectively depriving young animals of seemingly critical learning experiences or sensory stimulation. Should animals display some species-typical action following deprivation, then, presumably, the behavior could be labeled as unlearned or innate. In all, these studies seemed to show that animals displayed numerous adaptive responses at the very start, prior to any relevant experience. In a variety of ways, Spalding’s work anticipated 20th-century studies of innate behavior. Not only would the deprivation experiment be used as the primary means of detecting native tendencies by European zoologists and ethologists, but Spalding also showed evidence of what would later be called imprinting, critical period effects and evidence of behavioral maturation.

Reports of pure instinct did not go unchallenged. Lloyd Morgan ( 1896 ) questioned the accuracy of these reports in his own experimental work with young animals. In some cases, he failed to replicate the results and in other cases he found that instinctive behaviors were not as finely tuned to objects in the environment as had been claimed. Morgan’s research pointed to taking greater precision in identifying learned and instinctive components of behavior, but, like most at the turn of the 20th century , he did not question that animal behavior involved both learned and instinctive elements.

A focus on instinctive behaviors intensified in the 1890s as Weismann’s germ-plasm theory grew in popularity. More so than before, a sharp distinction was drawn between native and acquired characteristics, including behavior (Johnston, 1995 ). Although some psychologists continued to maintain neo-Lamarckian notions, most German (Burnham, 1972 ) and American (Cravens & Burnham, 1971 ) psychologists were quick to adopt Weismann’s theory. They envisioned a new natural science of psychology that would experimentally identify the germinally determined, invariable set of native psychological traits in species and their underlying physiological (neural) basis. However, whereas English-speaking psychologists tended to focus on how this view impacted our understanding of social institutions and its social implications, German psychologists were more interested in the longstanding philosophical implications of Weismann’s doctrine as it related to the differences (if any) between man and beast (Burnham, 1972 ).

Some anthropologists and sociologists, however, interpreted Weismann’s theory quite differently and used it elevate sociology as its own scientific discipline. In the 1890s, the French sociologist Emil Durkheim, for example, interpreted Weismann’s germinal determinants as a generic force on human behavior that influenced the development of general predispositions that are molded by the circumstances of life (Meloni, 2016 ). American anthropologists reached similar conclusions in the early 20th century (Cravens & Burnham, 1971 ). Because Weismann’s theory divorced biological inheritance from social inheritance, and because heredity was treated as a generic force, sociologists felt free to study social (eventually, “cultural”) phenomena without reference to biological or psychological concerns.

Anti-Instinct Movement in the 1920s

Despite their differences, in the first two decades of the 20th century both psychologists and sociologists generally assumed that humans and animals had some native tendencies or instincts. Concerns were even voiced that instinct had not received enough attention in psychology. Disagreements about instincts continued to focus on (the now centuries old debates of) how to conceptualize them. Were they complex reflexes, impulses, or motives to act, or should instinct be a mental faculty (like intuition), separate from reasoning and reflex (Herrnstein, 1972 )?

In America, the instinct concept came under fire following a brief paper in 1919 by Knight Dunlap titled “Are There Any Instincts?” His primary concern dealt with teleological definitions of instincts in which an instinct referred to all the activities involved in obtaining some end-state (e.g., instincts of crying, playing, feeding, reproduction, war, curiosity, or pugnacity). Defined in this way, human instincts were simply labels for human activities, but how these activities were defined was arbitrarily imposed by the researchers. Is feeding, for instance, an instinct, or is it composed of more basic instincts (like chewing and swallowing)? The arbitrariness of classifying human behavior had led to tremendous inconsistencies and confusion among psychologists.

Not all of the challenges to instinct dealt with its teleological usage. Some of the strongest criticisms were voiced by Zing-Yang Kuo throughout the 1920s. Kuo was a Chinese animal psychologist who studied under Charles Tolman at the University of California, Berkeley. Although Kuo’s attacks on instinct changed throughout the 1920s (see Honeycutt, 2011 ), he ultimately argued that all behaviors develop in experience-dependent ways and that appeals to instinct were statements of ignorance about how behaviors develop. Like Dunlap, he warned that instincts were labels with no explanatory value. To illustrate, after returning to China, he showed how the so-called rodent-killing instinct in cats often cited by instinct theorists is not found in kittens that are reared with rodents (Kuo, 1930 ). These kittens, instead, became attached to the rodents, and they resisted attempts to train rodent-killing. Echoing the point made by Guer, Kuo claimed that appeals to instinct served to stunt scientific inquiry into the developmental origins of behavior.

But Kuo did not just challenge the instinct concept. He also argued against labeling behaviors as “learned.” After all, whether an animal “learns” depends on the surrounding environmental conditions, the physiological and developmental status of the animal, and, especially, the developmental (or experiential) history of that animal. Understanding learning also required developmental analysis. Thus Kuo targeted the basic distinction between nature and nurture, and he was not alone in doing so (e.g., see Carmichael, 1925 ), but his call to reject it did not spread to mainstream American psychologists.

By the 1930s, the term instinct had fallen into disrepute in psychology, but experimental psychologists (including behaviorists) remained committed to a separation of native from acquired traits. If anything, the dividing line between native and acquired behaviors became more sharply drawn than before (Logan & Johnston, 2007 ). For some psychologists, instinct was simply rebranded in the less contentious (but still problematic) language of biological drives or motives (Herrnstein, 1972 ). Many other psychologists simply turned to describing native traits as due to “maturation” and/or “heredity” rather than “instinct.”

Fixed Action Patterns

The hereditarian instinct concept received a reboot in Europe in the 1930s with the rise of ethology led by Konrad Lorenz, Niko Tinbergen, and others. Just as animals inherit organs that perform specific functions, ethologists believed animals inherit behaviors that evolved to serve adaptive functions as well. Instincts were described as unlearned (inherited), blind, stereotyped, adaptive, fixed action patterns, impervious to change that are initiated (released) by specific stimuli in the environment.

Ethologists in 1930s and 1940s were united under the banner of innateness. They were increasingly critical of the trend by American psychologists (i.e., behaviorists) to focus on studying on how a limited number of domesticated species (e.g., white rat) responded to training in artificial settings (Burkhardt, 2005 ). Ethologists instead began with rich descriptions of animal behavior in more natural environments along with detailed analyses of the stimulus conditions that released the fixed action patterns. To test whether behavioral components were innate, ethologists relied primarily on the deprivation experiment popularized by Spalding in the 19th century . Using these methods (and others), ethologists identified numerous fascinating examples of instinctive behaviors, which captured mainstream attention.

In the early 1950s, shortly after ethology had gained professional status (Burkhardt, 2005 ), a series of challenges regarding instinct and innateness were put forth by a small cadre of North American behavioral scientists (e.g., T. C. Schneirla, Donald Hebb, Frank Beach). Arguably the most influential critique was voiced by comparative psychologist Daniel Lehrman ( 1953 ), who presented a detailed and damning critique of deprivation experiments on empirical and logical grounds. Lehrman explained that deprivation experiments isolate the animal from some but not all experiences. Thus deprivation experiments simply change what an animal experiences rather than eliminating experience altogether, and so they cannot possibly determine whether a behavior is innate (independent of experience). Instead, these experiments show what environmental conditions do not matter in the development of a behavior but do not speak to what conditions do matter .

Lehrman went on to argue that the whole endeavor to identify instinctive or innate behavior was misguided from the start. All behavior, according to Lehrman, develops from a history of interactions between an organism and its environment. If a behavior is found to develop in the absence of certain experiences, the researcher should not stop and label it as innate. Rather, research should continue to identify the conditions under which the behavior comes about. In line with Kuo, Lehrman repeated the warning that to label something as instinctive (or inherited or maturational) is a statement of ignorance about how that behavior develops and does more to stunt than promote research.

Lehrman’s critique created significant turmoil among ethologists. As a result, ethologists took greater care in using the term innate , and it led to new attempts to synthesize or re-envision learning and instinct .

Some of these attempts focused on an increased role for learning and experience in the ontogeny of species-typical behaviors. These efforts spawned significant cross-talk between ethologists and comparative psychologists to more thoroughly investigate behavioral development under natural conditions. Traditional appeals to instinct and learning (as classical and operant conditioning) were both found to be inadequate for explaining animal behavior. In their stead, these researchers focused more closely on how anatomical, physiological, experiential, and environmental conditions influenced the development of species-typical behaviors.

Tinbergen ( 1963 ) was among those ethologists who urged for greater developmental analysis of species-typical behaviors, and he included it as one of his four problems in the biological study of organisms, along with causation (mechanism), survival value (function), and evolution. Of these four problems, Tinbergen believed ethologists were especially well suited to study survival value, which he felt had been seriously neglected (Burkhardt, 2005 ).

The questions of survival value coupled with models of population genetics would gain significant momentum in the 1960s and 1970s in England and the United States with the rise of behavioral ecology and sociobiology (Griffiths, 2008 ). But because these new fields seemed to promote some kind of genetic determinism in behavioral development, they were met with much resistance and reignited a new round of nature–nurture debates in the 1970s (see Segerstrale, 2000 ).

However, not all ethologists abandoned the instinct concept. Lorenz, in particular, continued to defend the division between nature and nurture. Rather than speaking of native and acquired behaviors, Lorenz later spoke of two different sources of information for behavior (innate/genetic vs. acquired/environmental), which was more a subtle shift in language than it was an actual change in theory, as Lehrman later pointed out.

Some ethologists followed Lorenz’s lead and continued to maintain more of a traditional delineation between instinct and learning. Their alternative synthesis viewed learning as instinctive (Gould & Marler, 1987 ). They proposed that animals have evolved domain-specific “instincts to learn” that result from the its genetic predispositions and innate knowledge. To support the idea of instincts for learning, ethologists pointed to traditional ethological findings (on imprinting and birdsong learning), but they also drew from the growing body of work in experimental psychology that seemed to indicate certain types of biological effects on learning.

Biological Constraints and Preparedness

While ethology was spreading in Europe in the 1930s–1950s, behaviorism reigned in the United States. Just as ethologists were confronted with including a greater role of nurture in their studies, behaviorists were challenged to consider a greater role of nature.

Behaviorists assumed there to be some behavioral innateness (e.g., fixed action patterns, unconditioned reflexes, primary reinforcers and drives). But because behaviorists focused on learning, they tended to study animals in laboratory settings using biologically (or ecologically) irrelevant stimuli and responses to minimize any role of instinct (Johnston, 1981 ). It was widely assumed that these studies would identify general laws of learning that applied to all species regardless of the specific cues, reinforcers, and responses involved.

Challenges to the generality assumption began to accumulate in the 1960s. Some studies pointed to failures that occurred during conditioning procedures. Breland and Breland ( 1961 ), for example, reported that some complex behaviors formed through operant conditioning would eventually become “displaced” by conditioned fixed action patterns in a phenomenon they called “instinctive drift.” Studies of taste-aversion learning (e.g., Garcia & Koelling, 1966 ) also reported the failure of rats to associate certain events (e.g., flavors with shock or audiovisual stimuli with toxicosis).

Other studies were pointing to enhanced learning. In particular, it was found that rats could form strong conditioned taste aversions after only a single pairing between a novel flavor and illness. (This rapid “one trial learning” was a major focus in the research from Niko Tinbergen’s ethological laboratory.) Animals, it seemed, had evolved innate predispositions to form (or not form) certain associations.

In humans, studies of biological constraints on learning were mostly limited to fear conditioning. Evidence indicated that humans conditioned differently to (biologically or evolutionarily) fear-relevant stimuli like pictures of spiders or snakes than to fear-irrelevant stimuli like pictures of mushrooms or flowers (Ohman, Fredrikson, Hugdahl, & Rimmö, 1976 ).

These findings and others were treated as a major problem in learning theory and led to calls for a new framework to study learning from a more biologically oriented perspective that integrated the evolutionary history and innate predispositions of the species. These predispositions were described as biological “constraints” on, “preparedness,” or “adaptive specializations” for learning, all of which were consistent with the “instincts to learn” framework proposed by ethologists.

By the 1980s it was becoming clear that the biological preparedness/constraint view of learning suffered some limitations. For example, what constraints count as “biological” was questioned. It was well established that there were general constraints on learning associated with the intensity, novelty, and timing of stimuli. But, arbitrarily it seemed, these constraints were not classified as “biological” (Domjan & Galef, 1983 ). Other studies of “biological constraints” found that 5- and 10-day old rats readily learned to associated a flavor with shock (unlike in adults), but (like in adults) such conditioning was not found in 15-day-old rats (Hoffman & Spear, 1988 ). In other words, the constraint on learning was not present in young rats but developed later in life, suggesting a possible role of experience in bringing about the adult-like pattern.

Attempts to synthesize these alternatives led to numerous calls for more ecologically oriented approaches to learning not unlike the synthesis between ethology and comparative psychology in the 1960s. All ecological approaches to learning proposed that learning should be studied in the context of “natural” (recurrent and species-typical) problems that animals encounter (and have evolved to encounter) using ecologically meaningful stimuli and responses. Some argued (e.g., Johnston, 1981 ) that studies of learning should take place within the larger context of studying how animals develop and adapt to their surround. Others (Domjan & Galef, 1983 ) pointed to more of a comparative approach in studying animal learning in line with behavioral ecology that takes into account how learning can be influenced by the possible selective pressures faced by each species. Still, how to synthesize biological constraints (and evolutionary explanations) on learning with a general process approach remains a source of tension in experimental psychology.

Nativism in Mind: Innate Ideas

Nativism and empiricism in philosophy.

In the philosophy of mind, nature–nurture debates are voiced as debates between nativists and empiricists. Nativism is a philosophical position that holds that our minds have some innate (a priori to experience) knowledge, concepts, or structure at the very start of life. Empiricism, in contrast, holds that all knowledge derives from our experiences in the world.

However, rarely (if ever) were there pure nativist or empiricist positions, but the positions bespeak a persistent tension. Empiricists tended to eschew innateness and promote a view of the mental content that is built by general mechanisms (e.g., association) operating on sensory experiences, whereas nativists tend to promote a view of mind that contains domain-specific, innate processes and/or content (Simpson, Carruthers, Laurence, & Stich, 2005 ). Although the tension about mental innateness would loosen as empiricism gained prominence in philosophy and science, the strain never went away and would intensify again in the 20th century .

Nativism in 20th Century Psychology: The Case of Language Development

In the first half of the 20th century , psychologists generally assumed that knowledge was gained or constructed through experience with the world. This is not to say that psychologists did not assume some innate knowledge. The Swiss psychologist Jean Piaget, for example, believed infants enter the world with some innate knowledge structures, particularly as they relate to early sensory and motor functioning (see Piaget, 1971 ). But the bulk of his work dealt with the construction of conceptual knowledge as children adapt to their worlds. By and large, there were no research programs in psychology that sought to identify innate factors in human knowledge and cognition until the 1950s (Samet & Zaitchick, 2017 )

An interest in psychological nativism was instigated in large part by Noam Chomsky’s ( 1959 ) critique of B. F. Skinner’s book on language. To explain the complexity of language, he argued, we must view language as the knowledge and application of grammatical rules. He went on to claim that the acquisition of these rules could not be attributed to any general-purpose, learning process (e.g., reinforcement). Indeed, language acquisition occurs despite very little explicit instruction. Moreover, language is special in terms of its complexity, ease, and speed of acquisition by children and in its uniqueness to humans. Instead, he claimed that our minds innately contain some language-specific knowledge that kick-starts and promotes language acquisition. He later claimed this knowledge can be considered some sort of specialized mental faculty or module he called the “language acquisition device” (Chomsky, 1965 ) or what Pinker ( 1995 ) later called the “language instinct.”

To support the idea of linguistic nativism, Chomsky and others appealed to the poverty of the stimulus argument. In short, this argument holds that our experiences in life are insufficient to explain our knowledge and abilities. When applied to language acquisition, this argument holds children’s knowledge of language (grammar) goes far beyond the limited, and sometimes broken, linguistic events that children directly encounter. Additional evidence for nativism drew upon the apparent maturational quality of language development. Despite wide variations in languages and child-rearing practices across the world, the major milestones in language development appear to unfold in children in a universal sequence and timeline, and some evidence suggested a critical period for language acquisition.

Nativist claims about language sparked intense rebuttals by empiricist-minded psychologists and philosophers. Some of these retorts tackled the logical limitations of the poverty of stimulus argument. Others pointed to the importance of learning and social interaction in driving language development, and still others showed that language (grammatical knowledge) may not be uniquely human (see Tomasello, 1995 , for review). Nativists, in due course, provided their own rebuttals to these challenges, creating a persistent tension in psychology.

Extending Nativism Beyond Language Development

In the decades that followed, nativist arguments expanded beyond language to include cognitive domains that dealt with understanding the physical, psychological, and social worlds. Developmental psychologists were finding that infants appeared to be much more knowledgeable in cognitive tasks (e.g., on understanding object permanence) and skillful (e.g., in imitating others) than had previously been thought, and at much younger ages. Infants also showed a variety of perceptual biases (e.g., preference for face-like stimuli over equally complex non-face-like stimuli) from very early on. Following the standard poverty of the stimulus argument, these findings were taken as evidence that infants enter the world with some sort of primitive, innate, representational knowledge (or domain-specific neural mechanisms) that constrains and promotes subsequent cognitive development. The nature of this knowledge (e.g., as theories or as core knowledge), however, continues to be debated (Spelke & Kinzler, 2007 ).

Empiricist-minded developmental psychologists responded by demonstrating shortcomings in the research used to support nativist claims. For example, in studies of infants’ object knowledge, the behavior of infants (looking time) in nativist studies could be attributed to relatively simple perceptual processes rather than to the infants’ conceptual knowledge (Heyes, 2014 ). Likewise, reports of human neonatal imitation not only suffered from failures to replicate but could be explained by simpler mechanisms (e.g., arousal) than true imitation (Jones, 2017 ). Finally, studies of perceptual preferences found in young infants, like newborn preferences for face-like stimuli, may not be specific preferences for faces per se but instead may reflect simpler, nonspecific perceptual biases (e.g., preferences for top-heavy visual configurations and congruency; Simion & Di Giorgio, 2015 ).

Other arguments from empiricist-minded developmental psychologists focused on the larger rationale for inferring innateness. Even if it is conceded that young infants, like two-month-olds, or even two-day-olds, display signs of conceptual knowledge, there is no good evidence to presume the knowledge is innate. Their knowledgeable behaviors could still be seen as resulting from their experiences (many of which may be nonobvious to researchers) leading up to the age of testing (Spencer et al., 2009 ).

In the 21st century , there is still no consensus about the reality, extensiveness, or quality of mental innateness. If there is innate knowledge, can experience add new knowledge or only expand the initial knowledge? Can the doctrine of innate knowledge be falsified? There are no agreed-upon answers to these questions. The recurring arguments for and against mental nativism continue to confound developmental psychologists.

Maturation Theory

The emergence of bodily changes and basic behavioral skills sometimes occurs in an invariant, predictable, and orderly sequence in a species despite wide variations in rearing conditions. These observations are often attributed to the operation of an inferred, internally driven, maturational process. Indeed, 21st-century textbooks in psychology commonly associate “nature” with “maturation,” where maturation is defined as the predetermined unfolding of the individual from a biological or genetic blueprint. Environmental factors play a necessary, but fundamentally supportive, role in the unfolding of form.

Preformationism Versus Epigenesis in the Generation of Form

The embryological generation of bodily form was debated in antiquity but received renewed interest in the 17th century . Following Aristotle, some claimed that embryological development involved “epigenesis,” defined as the successive emergence of form from a formless state. Epigenesists, however, struggled to explain what orchestrated development without appealing to Aristotelean souls. Attempts were made to invoke to natural causes like physical and chemical forces, but, despite their best efforts, the epigenesists were forced to appeal to the power of presumed, quasi-mystical, vitalistic forces (entelechies) that directed development.

The primary alternative to epigenesis was “preformationism,” which held that development involved the growth of pre-existing form from a tiny miniature (homunculus) that formed immediately after conception or was preformed in the egg or sperm. Although it seems reasonable to guess that the invention and widespread use of the microscope would immediately lay to rest any claim of homuncular preformationism, this was not the case. To the contrary, some early microscopists claimed to see signs of miniature organisms in sperm or eggs, and failures to find these miniatures were explained away (e.g., the homunculus was transparent or deflated to the point of being unrecognizable). But as microscopes improved and more detailed observations of embryological development were reported in the late 18th and 19th centuries , homuncular preformationism was finally refuted.

From Preformationism to Predeterminism

Despite the rejection of homuncular preformationism, preformationist appeals can be found throughout the 19th century . One of the most popular preformationist theories of embryological development was put forth by Ernst Haeckel in the 1860s (Gottlieb, 1992 ). He promoted a recapitulation theory (not original to Haeckel) that maintained that the development of the individual embryo passes through all the ancestral forms of its species. Ontogeny was thought to be a rapid, condensed replay of phylogeny. Indeed, for Haeckel, phylogenesis was the mechanical cause of ontogenesis. The phylogenetic evolution of the species created the maturational unfolding of embryonic form. Exactly how this unfolding takes place was less important than its phylogenetic basis.

Most embryologists were not impressed with recapitulation theory. After all, the great embryologist Karl Ernst von Baer ( 1792–1876 ) had refuted strict recapitulation decades earlier. Instead, there was greater interest in how best to explain the mechanical causes of development ushering in a new “experimental embryology.” Many experimental embryologists followed the earlier epigenesists by discussing vitalistic forces operating on the unorganized zygote. But it soon became clear that the zygote was structured, and many people believed the zygote contained special (unknown) substances that specified development. Epigenesis-minded experimental embryologists soon warned that the old homuncular preformationism was being transformed into a new predetermined preformationism.

As a result, the debates between preformationism and epigenesis were reignited in experimental embryology, but the focus of these debates shifted to the various roles of nature and nurture during development. More specifically, research focused on the extent to which early cellular differentiation was predetermined by factors internal to cells like chromosomes or cytoplasm (preformationism, nature) or involved factors (e.g., location) outside of the cell (epigenesis, nurture). The former emphasized reductionism and developmental programming, whereas the latter emphasized some sort of holistic, regulatory system responsive to internal and external conditions. The tension between viewing development as predetermined or “epigenetic” persists into the 21st century .

Preformationism gained momentum in the 20th century following the rediscovery of Mendel’s studies of heredity and the rapid rise of genetics, but not because of embryological research on the causes of early differentiation. Instead, preformationism prevailed because it seemed embryological research on the mechanisms of development could be ignored in studies of hereditary patterns.

The initial split between heredity and development can be found in Galton’s speculations but is usually attributed to Weismann’s germ-plasm theory. Weismann’s barrier seemed to posit that the germinal determinants present at conception would be the same, unaltered determinants transmitted during reproduction. This position, later dubbed as “Weismannism,” was ironically not one promoted by Weismann. Like nearly all theorists in the 19th century , he viewed the origins of variation and heredity as developmental phenomena (Amundson, 2005 ), and he claimed that the germ-plasm could be directly modified in the lifetime of the organism by environmental (e.g., climactic and dietary) conditions (Winther, 2001 ). Still, Weismann’s theory treated development as a largely predetermined affair driven by inherited, germinal determinants buffered from most developmental events. As such, it helped set the stage for a more formal divorce between heredity and development with the rise of Mendelism in the early 20th century .

Mendel’s theory of heredity was exceptional in how it split development from heredity (Amundson, 2005 ). More so than in Weismann’s theory, Mendel’s theory assumed that the internal factors that determine form and are transmitted across generations remain unaltered in the lifetime of the organism. To predict offspring outcomes, one need only know the combination of internal factors present at conception and their dominance relations. Exactly how these internal factors determined form could be disregarded. The laws of hereditary transmission of the internal factors (e.g., segregation) did not depend on the development or experiences of the organism or the experiences the organism’s ancestors. Thus the experimental study of heredity (i.e., breeding) could proceed without reference to ancestral records or embryological concerns (Amundson, 2000 ). By the mid-1920s, the Mendelian factors (now commonly called “genes”) were found to be structurally arranged on chromosomes, and the empirical study of heredity (transmission genetics) was officially divorced from studies of development.

The splitting of heredity and development found in Mendel’s and Weismann’s work met with much resistance. Neo-Lamarckian scientists, especially in the United States (Cook, 1999 ) and France (Loison, 2011 ), sought unsuccessfully to experimentally demonstrate the inheritance of acquired characteristics into the 1930s.

In Germany during the 1920s and 1930s, resistance to Mendelism dealt with the chromosomal view of Mendelian heredity championed by American geneticists who were narrowly focused on studying transmission genetics at the expense of developmental genetics. German biologists, in contrast, were much more interested in the broader roles of genes in development (and evolution). In trying to understand how genes influence development, particularly of traits of interest to embryologists, they found the Mendelian theory to be lacking. In the decades between the world wars, German biologists proposed various expanded views of heredity that included some form of cytoplasmic inheritance (Harwood, 1985 ).

Embryologists resisted the preformationist view of development throughout the early to mid- 20th century , often maintaining no divide between heredity and development, but their objections were overshadowed by genetics and its eventual synthesis with evolutionary theory. Consequently, embryological development was treated by geneticists and evolutionary biologists as a predetermined, maturational process driven by internal, “genetic” factors buffered from environmental influence.

Maturation Theory in Psychology

Maturation theory was applied to behavioral development in the 19th century in the application of Haeckel’s recapitulation theory. Some psychologists believed that the mental growth of children recapitulated the history of the human race (from savage brute to civilized human). With this in mind, many people began to more carefully document child development. Recapitulationist notions were found in the ideas of many notable psychologists in the 19th and early 20th centuries (e.g., G. S. Hall), and, as such, the concept played an important role in the origins of developmental psychology (Koops, 2015 ). But for present purposes what is most important is that children’s mental and behavioral development was thought to unfold via a predetermined, maturational process.

With the growth of genetics, maturational explanations were increasingly invoked to explain nearly all native and hereditary traits. As the instinct concept lost value in the 1920s, maturation theory gained currency, although the shift was largely a matter of semantics. For many psychologists, the language simply shifted from “instinct versus learning” to “maturation versus practice/experience” (Witty & Lehman, 1933 ).

Initial lines of evidence for maturational explanations of behavior were often the same as those that justified instinct and native traits, but new embryological research presented in the mid-1920s converged to show support for strict maturational explanations of behavioral development. In these experiments (see Wyman, 2005 , for review), spanning multiple laboratories, amphibians (salamanders and frogs) were exposed to drugs that acted as anesthetics and/or paralytics throughout the early stages of development, thus reducing sensory experience and/or motor practice. Despite the reduced sensory experiences and being unable to move, these animals showed no delays in the onset of motor development once the drugs wore off.

This maturational account of motor development in amphibians fit well with contemporaneous studies of motor development in humans. The orderly, invariant, and predictable (age-related) sequential appearance of motor skills documented in infants reared under different circumstances (in different countries and across different decades) was seen as strong evidence for a maturational account. Additional evidence was reported by Arnold Gessell and Myrtle McGraw, who independently presented evidence in the 1920s to show that the pace and sequence of motor development in infancy were not altered by special training experiences. Although the theories of these maturation theorists were more sophisticated when applied to cognitive development, their work promoted a view in which development was primarily driven by neural maturation rather than experience (Thelen, 2000 ).

Critical and Sensitive Periods

As the maturation account of behavioral development gained ground, it became clear that environmental input played a more informative role than had previously been thought. Environmental factors were found to either disrupt or induce maturational changes at specific times during development. Embryological research suggested that there were well-delineated time periods of heightened sensitivity in which specific experimental manipulations (e.g., tissue transplantations) could induce irreversible developmental changes, but the same manipulation would have no effect outside of that critical period.

In the 1950s–1960s a flurry of critical period effects were reported in birds and mammals across a range of behaviors including imprinting, attachment, socialization, sensory development, bird song learning, and language development (Michel & Tyler, 2005 ). Even though these findings highlighted an important role of experience in behavioral development, evidence of critical periods was usually taken to imply some rigid form of biological determinism (Oyama, 1979 ).

As additional studies were conducted on critical period effects, it became clear that many of the reported effects were more gradual, variable, experience-dependent, and not necessarily as reversible as was previously assumed. In light of these reports, there was a push in the 1970s (e.g., Connolly, 1972 ) to substitute “sensitive period” for “critical period” to avoid the predeterminist connotations associated with the latter and to better appreciate that these periods simply describe (not explain) certain temporal aspects of behavioral development. As a result, a consensus emerged that behaviors should not be attributed to “time” or “age” but to the developmental history and status of the animal under investigation (Michel & Tyler, 2005 ).

Heredity and Genetics

In the decades leading up to and following the start of the 20th century , it was widely assumed that many psychological traits (not just instincts) were inherited or “due to heredity,” although the underlying mechanisms were unknown. Differences in intelligence, personality, and criminality within and between races and sexes were largely assumed to be hereditary and unalterable by environmental intervention (Gould, 1996 ). The evidence to support these views in humans was often derived from statistical analyses of how various traits tended to run in families. But all too frequently, explanations of data were clouded by pre-existing, hereditarian assumptions.

Human Behavioral Genetics

The statistical study of inherited human (physical, mental, and behavioral) differences was pioneered by Galton ( 1869 ). Although at times Galton wrote that nature and nurture were so intertwined as to be inseparable, he nevertheless devised statistical methods to separate their effects. In the 1860s and 1870s, Galton published reports purporting to show how similarities in intellect (genius, talent, character, and eminence) in European lineages appeared to be a function of degree of relatedness. Galton considered, but dismissed, environmental explanations of his data, leading him to confirm his belief that nature was stronger than nurture.

Galton also introduced the use of twin studies to tease apart the relative impact of nature versus nurture, but the twin method he used was markedly different from later twin studies used by behavioral geneticists. Galton tracked the life history of twins who were judged to be very similar or very dissimilar near birth (i.e., by nature) to test the power of various postnatal environments (nurture) that might make them more or less similar over time. Here again, Galton concluded that nature overpowers nurture.

Similar pedigree (e.g., the Kallikak study; see Zenderland, 2001 ) and twin studies appeared in the early 1900s, but the first adoption study and the modern twin method (which compares monozygotic to dizygotic twin pairs) did not appear until the 1920s (Rende, Plomin, & Vandenberg, 1990 ). These reports led to a flurry of additional work on the inheritance of mental and behavioral traits over the next decade.

Behavioral genetic research peaked in the 1930s but rapidly lost prominence due in large part to its association with the eugenics movement (spearheaded by Galton) but also because of the rise and eventual hegemony of behaviorism and the social sciences in the United States. Behavioral genetics resurged in the 1960s with the rising tide of nativism in psychology, and returned to its 1930s-level prominence in the 1970s (McGue & Gottesman, 2015 ).

The resurgence brought with a new statistical tool: the heritability statistic. The origins of heritability trace back to early attempts to synthesize Mendelian genetics with biometrics by Ronald Fisher and others. This synthesis ushered in a new field of quantitative genetics and it marked a new way of thinking about nature and nurture. The shift was to no longer think about nature and nurture as causes of traits in individuals but as causes of variation in traits between populations of individuals. Eventually, heritability came to refer to the amount of variance in a population sample that could be statistically attributed to genetic variation in that sample. Kinship (especially twin) studies provided seemingly straightforward ways of partitioning variation in population trait attributes into genetic versus environmental sources.

Into the early 21st century , hundreds of behavioral genetic studies of personality, intelligence, and psychopathology were reported. With rare exceptions, these studies converge to argue for a pervasive influence of genetics on human psychological variation.

These studies have also fueled much controversy. Citing in part behavioral genetic research, the educational psychologist Arthur Jensen ( 1969 ) claimed that the differences in intelligence and educational achievement in the United States between black and white students appeared to have a strong genetic basis. He went on to assume that because these racial differences appeared hereditary, they were likely impervious to environmental (educational) intervention. His article fanned the embers of past eugenics practices and ignited fiery responses (e.g., Hirsch, 1975 ). The ensuing debates not only spawned a rethinking of intelligence and how to measure it, but they ushered in a more critical look at the methods and assumptions of behavioral genetics.

Challenges to Behavioral Genetics

Many of the early critiques of behavioral genetics centered on interpreting the heritability statistic commonly calculated in kinship (family, twin, and adoption) studies. Perhaps more so than any other statistic, heritability has been persistently misinterpreted by academics and laypersons alike (Lerner, 2002 ). Contrary to popular belief, heritability tells us nothing about the relative impact of genetic and environmental factors on the development of traits in individuals. It deals with accounting for trait variation between people, not the causes of traits within people. As a result, a high heritability does not indicate anything about the fixity of traits or their imperviousness to environmental influence (contra Jensen), and a low heritability does not indicate an absence of genetic influence on trait development. Worse still, heritability does not even indicate anything about the role of genetics in generating the differences between people.

Other challenges to heritability focused not on its interpretation but on its underlying computational assumptions. Most notably, heritability analyses assume that genetic and environmental contributions to trait differences are independent and additive. The interaction between genetic and environmental factors were dismissed a priori in these analyses. Studies of development, however, show that no factor (genes, hormones, parenting, schooling) operates independently, making it impossible to quantify how much of a given trait in a person is due to any causal factor. Thus heritability analyses are bound to be misleading because they are based on biologically implausible and logically indefensible assumptions about development (Gottlieb, 2003 ).

Aside from heritability, kinship studies have been criticized for not being able to disentangle genetic and environmental effects on variation. It had long been known that that in family (pedigree) studies, environmental and genetic factors are confounded. Twin and adoption studies seemed to provide unique opportunities to statistically disentangle these effects, but these studies are also deeply problematic in assumptions and methodology. There are numerous plausible environmental reasons for why monozygotic twin pairs could resemble each other more than dizygotic twin pairs or why adoptive children might more closely resemble their biological than their adoptive parents (Joseph & Ratner, 2013 ).

A more recent challenge to behavioral genetics came from an unlikely source. Advances in genomic scanning in the 21st century made it possible in a single study to correlate thousands of genetic polymorphisms with variation in the psychological profiles (e.g., intelligence, memory, temperament, psychopathology) of thousands of people. These “genome-wide association” studies seemed to have the power and precision to finally identify genetic contributions to heritability at the level of single nucleotides. Yet, these studies consistently found only very small effects.

The failure to find large effects came to be known as the “missing heritability” problem (Maher, 2008 ). To account for the missing heritability, some behavioral geneticists and molecular biologists asserted that important genetic polymorphisms remain unknown, they may be too rare to detect, and/or that current studies are just not well equipped to handle gene–gene interactions. These studies were also insensitive to epigenetic profiles (see the section on Behavioral Epigenetics), which deal with differences in gene expression. Even when people share genes, they may differ in whether those genes get expressed in their lifetimes.

But genome-wide association studies faced an even more problematic issue: Many of these studies failed to replicate (Lickliter & Honeycutt, 2015 ). For those who viewed heritability analyses as biologically implausible, the small effect sizes and failures to replicate in genome-wide association studies were not that surprising. The search for independent genetic effects was bound to fail, because genes simply do not operate independently during development.

Behavioral Epigenetics

Epigenetics was a term coined in the 1940s by the developmental biologist Conrad Waddington to refer to a new field of study that would examine how genetic factors interact with local environmental conditions to bring about the embryological development of traits. By the end of the 20th century , epigenetics came to refer to the study of how nongenetic, molecular mechanisms physically regulate gene expression patterns in cells and across cell lineages. The most-studied mechanisms involve organic compounds (e.g., methyl-groups) that physically bind to DNA or the surrounding proteins that package DNA. The addition or removal of these compounds can activate or silence gene transcription. Different cell types have different, stable epigenetic markings, and these markings are recreated during cell division so that cells so marked give rise to similar types of cells. Epigenetic changes were known to occur during developmental periods of cellular differentiation (e.g., during embryogenesis), but not until 2004 was it discovered that these changes can occur at other periods in the life, including after birth (Roth, 2013 )

Of interest to psychologists were reports that different behavioral and physiological profiles (e.g., stress reactivity) of animals were associated with different epigenetic patterns in the nervous system (Moore, 2015 ). Furthermore, these different epigenetic patterns could be established or modified by environmental factors (e.g., caregiving practices, training regimes, or environmental enrichment), and, under certain conditions, they remain stable over long periods of time (from infancy to adulthood).

Because epigenetic research investigates the physical interface between genes and environment, it represents an exciting advance in understanding the interaction of nature and nurture. Despite some warnings that the excitement over behavioral epigenetic research may be premature (e.g., Miller, 2010 ), for many psychologists, epigenetics underscores how development involves both nature and nurture.

For others, what is equally exciting is the additional evidence epigenetics provides to show that the genome is an interactive and regulated system. Once viewed as the static director of development buffered from environment influence, the genome is better described as a developing resource of the cell (Moore, 2015 ). More broadly, epigenetics also points to how development is not a genetically (or biologically) predetermined affair. Instead, epigenetics provides additional evidence that development is a probabilistic process, contingent upon factors internal and external to the organism. In this sense, epigenetics is well positioned to help dissolve the nature–nurture dichotomy.

Beyond Nature–Nurture

In the final decades of the 20th century , a position was articulated to move beyond the dichotomous nature–nurture framework. The middle-ground position on nature–nurture did not seem up to the task of explaining the origins of form, and it brought about more confusion than clarity. The back-and-forth (or balanced) pendulum between nature- and nurture-based positions throughout history had only gone in circles. Moving forward would require moving beyond such dichotomous thinking (Johnston, 1987 ).

The anti-dichotomy position, referred to as the Developmentalist tradition, was expressed in a variety of systems-based, metatheoretical approaches to studying development, all of which extended the arguments against nature–nurture expressed earlier by Kuo and Lehrman. The central problem with all nativist claims according to Developmentalists is a reliance on preformationism (or predeterminism).

The problem with preformationism, they argue, besides issues of evidence, is that it is an anti-developmental mindset. It presumes the existence of the very thing(s) one wishes to explain and, consequently, discourages developmental analyses. To claim that some knowledge is innate effectively shuts down research on the developmental origins of that knowledge. After all, why look for the origins of conceptual knowledge if that knowledge is there all along? Or why search for any experiential contributions to innate behaviors if those behaviors by definition develop independently of experience? In the words of Developmentalists Thelen and Adolph ( 1992 ), nativism “leads to a static science, with no principles for understanding change or for confronting the ultimate challenge of development, the source of new forms in structure and function” (p. 378).

A commitment to maturational theory is likely one of the reasons why studies of motor development remained relatively dormant for decades following its heyday in the 1930–1940s (Thelen, 2000 ). Likewise, a commitment to maturational theory also helps explain the delay in neuroscience to examine how the brain physically changes in response to environmental conditions, a line of inquiry that only began in the 1960s.

In addition to the theoretical pitfalls of nativism, Developmentalists point to numerous studies that show how some seemingly native behaviors and innate constraints on learning are driven by the experiences of animals. For example, the comparative psychologist Gilbert Gottlieb ( 1971 ) showed that newly hatched ducklings display a naïve preference for a duck maternal call over a (similarly novel) chicken maternal call (Gottlieb, 1971 ), even when duck embryos were repeatedly exposed to the chicken call prior to hatching (Gottlieb, 1991 ). It would be easy to conclude that ducklings have an innate preference to approach their own species call and that they are biologically constrained (contraprepared) in learning a chicken call. However, Gottlieb found that the naïve preference for the duck call stemmed from exposure to the duck embryos’ own (or other) vocalizations in the days before hatching (Gottlieb, 1971 ). Exposure to these vocalizations not only made duck maternal calls more attractive, but it hindered the establishment of a preference for heterospecific calls. When duck embryos were reared in the absence of the embryonic vocalizations (by devocalizing embryos in ovo ) and exposed instead to chicken maternal calls, the newly hatched ducklings preferred chicken over duck calls (Gottlieb, 1991 ). These studies clearly showed how seemingly innate, biologically based preferences and constraints on learning derived from prenatal sensory experiences.

For Developmentalists, findings like these suggest that nativist explanations of any given behavior are statements of ignorance about how that behavior actually develops. As Kuo and Lehrman made clear, nativist terms are labels, not explanations. Although such appeals are couched in respectable, scientific language (e.g., “X is due to maturation, genes, or heredity”), they argue it would be more accurate simply to say that “We don’t know what causes X” or that “X is not due to A, B, or C.” Indeed, for Developmentalists, the more we unpack the complex dynamics about how traits develop, the less likely we are to use labels like nature or nurture (Blumberg, 2005 ).

On the other hand, Developmentalists recognize that labeling a behavior as “learned” also falls short as an explanatory construct. The empiricist position that knowledge or behavior is learned does not adequately take into account that what is learned and how easily something is learned depends on (a) the physiological and developmental status of the person, (b) the nature of the surrounding physical and social context in which learning takes place, and the (c) experiential history of the person. The empiricist tendency to say “X is learned or acquired through experience” can also short-circuit developmental analyses in the same way as nativist claims.

Still, Developmentalists appreciate that classifying behaviors can be useful. For example, the development of some behaviors may be more robust, reliably emerging across a range of environments and/or remaining relatively resistant to change, whereas others are more context-specific and malleable. Some preferences for stimuli require direct experience with those stimuli. Other preferences require less obvious (indirect) types of experiences. Likewise, it can still be useful to describe some behaviors in the ways shown in Table 1 . Developmentalists simply urge psychologists to resist the temptation to treat these behavioral classifications as implying different kinds of explanations (Johnston, 1987 ).

Rather than treat nature and nurture as separate developmental sources of causation (see Figure 1 ), Developmentalists argue that a more productive way of thinking about nature–nurture is to reframe the division as that between product and process (Lickliter & Honeycutt, 2015 ). The phenotype or structure (one’s genetic, epigenetic, anatomical, physiological, behavioral, and mental profile) of an individual at any given time can be considered one’s “nature.” “Nurture” then refers to the set of processes that generate, maintain, and transform one’s nature (Figure 2 ). These processes involve the dynamic interplay between phenotypes and environments.

Figure 2. The developmentalist alternative view of nature–nurture as product–process. Developmentalists view nature and nurture not as separate sources of causation in development (see Figure 1 ) but as a distinction between process (nurture) and product (nature).

It is hard to imagine any set of findings that will end debates about the roles of nature and nurture in human development. Why? First, more so than other assumptions about human development, the nature–nurture dichotomy is deeply entrenched in popular culture and the life sciences. Second, throughout history, the differing positions on nature and nurture were often driven by other ideological, philosophical, and sociopolitical commitments. Thus the essential source of tension in debates about nature–nurture is not as much about research agendas or evidence as about basic differences in metatheoretical positions (epistemological and ontological assumptions) about human behavior and development (Overton, 2006 ).

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Institute of Medicine (US) Forum on Neuroscience and Nervous System Disorders. From Molecules to Minds: Challenges for the 21st Century: Workshop Summary. Washington (DC): National Academies Press (US); 2008.

From Molecules to Minds: Challenges for the 21st Century: Workshop Summary.

• Hardcopy Version at National Academies Press

Grand Challenge: Nature Versus Nurture: How Does the Interplay of Biology and Experience Shape Our Brains and Make Us Who We Are?

Nature vs. nurture is one of the oldest questions in science. The answer is not an either/or, but rather it is both nature and nurture, acting in various degrees.

As summarized below in greater detail, many workshop participants—including Hyman, Marder, and Michael Greenberg, chair of the Department of Neurobiology at Harvard Medical School—chose to highlight the nature versus nurture question as one of the Grand Challenges of the field, but in so doing, they put a twist on the question, asking: How does the interplay of biology and experience shape our brains and make us who we are?

The key word there is “interplay.” “Interplay” suggests, and modern research in neuroscience demands, that there is a back and forth pattern between nature and nurture, a dynamic system that involves a continuous feedback loop shaping the physical structure of our brains.

• Brain Plasticity

Thirty years ago, the working assumption in neuroscience was this: People are born with a set number of neurons, hardwired in a certain way, and brain function is essentially all downhill from there. We spend our lifetimes losing connections and neurons—the brain slowly falling apart until we die.

Except it is not true. In 1998, Fred “Rusty” Gage, working out of the Laboratory of Genetics at the Salk Institute, showed that the human brain can and does produce new nerve cells into adulthood ( Eriksson et al., 1998 ). In mice, he showed that exercise could increase the rate of neurogenesis, showing that the system is not fixed, but responds itself to experience and the outside world. The discovery of neurogenesis and an improved understanding of neuroplasticity—the ability of the brain to shape, form, eliminate, and strengthen new connections throughout life—has completely recast the question of nature versus nurture.

“Neurons can change their connectivity,” explained Blakemore. “They can change the strength of their connections. They can change the morphology of their connections. They can do it not necessarily just in early stages of life, although that is especially exaggerated, but probably throughout life responding to new environments and experiences.”

New research shows, for instance, that the number and strength of connections we have in the brain is determined by how often those connections are stimulated. The brain, if you will, has a “use it or lose it” approach to neurological maintenance.

Genetic programming also plays a key role. In most cases, the initial formation of a synapse occurs independent of stimulation. But if that synapse is not used, the brain will “prune” or eliminate it. Conversely, the more often a connection is used, the stronger it becomes in a physical sense, with more dendritic spines connecting to one another and a stronger net connection over time.

On the developmental side, researchers now understand the critical role that sensory input plays in shaping the wiring of the brain from the earliest days. Blakemore discussed work in his lab on the development of neural wiring in mice. Researchers have known since the 1960s that the neurons connected to the ultrasensitive whiskers of mice align themselves in a format called “barrel fields.” Each of these barrel fields is connected to a single whisker, although how or why they influence function is unknown. Blakemore showed that if you removed a clump of whiskers at an early age, the segment of the brain linked to that area never develops the barrel structure.

Similar research has shown in mice that if you tape one eye shut from birth, the mouse never gains the ability to see from that eye—it needs the stimulation to develop. However, if you tape shut the eye of an adult mouse for a similar period of time, vision is not affected.

All this seems to point the finger toward experience, but of course, the system really works as a complete feedback loop.

“We used to think . . . that the capacity of the brain to change its connections was an entirely independent process from the genetic regulation of structure,” said Blakemore. “But, of course, that cannot be the case. If adaptive change is possible, that must be the consequence of having molecular mechanisms that mediate those changes. Plasticity is a characteristic that has been selected for, so there must be genes for plasticity.”

In the case of barrel fields, Blakemore’s lab and other investigators have identified a number of molecules and genes that appear to be involved in mediating between incoming information for the whiskers and the anatomical changes necessary to produce the barrel field.

Understanding how this interplay works has huge implications for understanding how our brain develops and changes over time, and raises a number of interesting questions. Marder, for instance, asked how the brain can be so plastic and yet still retain memories over time.

Plasticity, however, is just one half of the equation; the underlying genetics are critically important, and new techniques and technologies make this a particularly interesting time to address these questions. For instance, modern, high-throughput gene-profiling technologies allow researchers to figure out all of the underlying transcriptions in a neuron, and see how these are manifest in the body.

Understanding the interplay of biology and experience on learning and development will surely require understanding the biological processes that cause changes in individual neurons and synapses. But this is only part of the puzzle. We must also understand the control of learning processes at a system-wide level in the brain. How does the brain orchestrate the right set of neural synaptic updates based on training experiences we encounter over our lifetime? Given the tremendous number of synapses in the brain, it is unlikely that a purely bottom-up approach will suffice to answer this question.

A complementary approach to studying experience-based learning at a system level relies on machine learning algorithms that have been developed to allow robots to learn from experience, described Mitchell. One intriguing study has shown that temporal-difference learning algorithms, which enable robots successfully to learn control strategies such as how to fly helicopters autonomously, can be used to predict the neural activity of dopamine-based systems in the human brain that are involved in reward-based learning ( Schultz et al., 1997 ; Seymour et al., 2004 ; Doya, 2008 ). The integration of such system-level computational models alongside new research into synaptic plasticity offers an opportunity to examine the interplay of biology and experience on learning and development from multiple perspectives.

New tools will allow researchers to understand how variability between different genes and neurons and neuronal activity could influence behavior and capabilities across different people, the researchers said. Who we are is not only influenced by the yes/no expression of genes, but also the specific levels of expression among different genes, which in turn influences neuronal activity.

• Gene-Environment Interactions

Nature and nurture are not simply additive interactions that result in a particular behavior, but rather a complex interplay of many factors. Nature includes not only the usual factors—parents, homes, what people learn—but also many other factors that individuals are exposed to routinely in their daily environments. As Marder emphasized, we cannot simply assume that gene X produces behavior Y. Instead as Bialek described, there are often many additional factors that directly and indirectly interact with gene X and ultimately influence variants in behavior. These variants define individuality.

As previously described, it has been known for almost 50 years that experience from the outside environment shapes our brain. This comes initially from the original work of Nobel Laureates David Hubel and Torsten Wiesel who studied how information is sensed and processed in the part of the brain responsible for vision. As Greenberg commented, the field is now at a point where we could in the next 10 years attain a significant mechanistic understanding of how the environment impinges directly on our genes to give rise to a malleable organ that allows us to adapt and change.

• Huge Clinical Importance

Multiple participants at the workshop—including Nora Volkow, director of the National Institute on Drug Abuse; Joseph Takahashi, investigator of the Howard Hughes Medical Institute and Northwestern University; Lichtman; and Coyle—highlighted the role of genetics in shaping the brain as one of the fundamental challenges for neuroscience, both for its basic scientific interest and for its practical applications: Understanding how genes and experience come together to impact the brain could significantly alter how we think about treating neurological disease. Many of the most common neurological and mental health disorders—schizophrenia, bipolar disorder, autism, Parkinson’s disease, multiple sclerosis, Alzheimer’s disease—are complex genetic disorders that are influenced by environmental factors.

Alcino Silva, professor in the Departments of Neurobiology, Psychiatry and Psychology at the University of California, Los Angeles, showcased research from his lab showing he could treat and reverse developmental disorders in adult mice. This finding is worth repeating because it is so contrary to our general thinking on developmental disorders: Scientists working out of Silva’s lab have been able to reverse the impacts of the developmental disorder NF-1 (Neurofibromatosis type 1), which is caused by genetic malfunction, by treating the pathology of the disease in adult mice. These mice, which have obvious cognitive deficits, regain mental function when treated; Silva has advanced the study into human clinical trials.

The applications of this vein of study extend beyond developmental disorders. A growing body of evidence is revealing a massive feedback loop among genetics, neurological structure, experience, and disease. You are three times more likely to die from a heart attack if you are depressed than if you are not, for instance, and depression has a huge impact on diabetes as well, stated Coyle.

Taking a step backward, clinical data also show that people who experience multiple stressful episodes in their lives tend to suffer from clinical depression. But there is tremendous variation: Some people are resistant to stress and others are not.

“It turns out that the pattern is correlated with a polymorphic variation in one particular gene, the gene for the transporter for serotonin, a transmitter which is known to be involved in regulating mood,” explained Blakemore.

How do genes work in the brain to determine our resilience to stress, and how can those capabilities be monitored and modulated for better health?

• The Way Forward

Asking these kinds of questions was not realistic 10 or even 5 years ago. The advent of high-throughput gene profiling and the growing sophistication of our ability to manipulate genes in animal models lets us, for the first time, explore the role that genes play in both creating and modulating our neural structures. At the same time, new imaging techniques and technologies like channel rhodopsin “light switches” let us better characterize neural systems and their response to the world around us, and to begin to plumb the tremendous feedback loop among genes, experience, and the physical activity in the brain.

Until quite recently, these have remained philosophical questions, commented Marder. However, the field of neuroscience is now in a position—through all the molecular, connectomics, and technological advances—to put these questions on firm mechanistic, biological bases, and to attack them scientifically.

• Cite this Page Institute of Medicine (US) Forum on Neuroscience and Nervous System Disorders. From Molecules to Minds: Challenges for the 21st Century: Workshop Summary. Washington (DC): National Academies Press (US); 2008. Grand Challenge: Nature Versus Nurture: How Does the Interplay of Biology and Experience Shape Our Brains and Make Us Who We Are?
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Nature vs. Nurture

Reviewed by Psychology Today Staff

The expression “nature vs. nurture” describes the question of how much a person's characteristics are formed by either “nature” or “nurture.” “Nature” means innate biological factors (namely genetics ), while “nurture” can refer to upbringing or life experience more generally.

Traditionally, “nature vs. nurture” has been framed as a debate between those who argue for the dominance of one source of influence or the other, but contemporary experts acknowledge that both “nature” and “nurture” play a role in psychological development and interact in complex ways.

• The Meaning of Nature vs. Nurture
• The Nature-vs.-Nurture Debate
• Identifying Genetic and Environmental Factors

The wording of the phrase “nature vs. nurture” makes it seem as though human individuality— personality traits, intelligence , preferences, and other characteristics—must be based on either the genes people are born with or the environment in which they grew up. The reality, as scientists have shown, is more complicated, and both these and other factors can help account for the many ways in which individuals differ from each other.

The words “nature” and “nurture” themselves can be misleading. Today, “ genetics ” and “environment” are frequently used in their place—with one’s environment including a broader range of experiences than just the nurturing received from parents or caregivers. Further, nature and nurture (or genetics and environment) do not simply compete to influence a person, but often interact with each other; “nature and nurture” work together. Finally, individual differences do not entirely come down to a person’s genetic code or developmental environment—to some extent, they emerge due to messiness in the process of development as well.

A person’s biological nature can affect a person’s experience of the environment. For example, a person with a genetic disposition toward a particular trait, such as aggressiveness, may be more likely to have particular life experiences (including, perhaps, receiving negative reactions from parents or others). Or, a person who grows up with an inclination toward warmth and sociability may seek out and elicit more positive social responses from peers. These life experiences could, in turn, reinforce an individual’s initial tendencies. Nurture or life experience more generally may also modify the effects of nature—for example, by expanding or limiting the extent to which a naturally bright child receives encouragement, access to quality education , and opportunities for achievement.

Epigenetics—the science of modifications in how genes are expressed— illustrates the complex interplay between “nature” and “nurture.” An individual’s environment, including factors such as early-life adversity, may result in changes in the way that parts of a person’s genetic code are “read.” While these epigenetic changes do not override the important influence of genes in general, they do constitute additional ways in which that influence is filtered through “nurture” or the environment.

Theorists and researchers have long battled over whether individual traits and abilities are inborn or are instead forged by experiences after birth. The debate has had broad implications: The real or perceived sources of a person’s strengths and vulnerabilities matter for fields such as education, philosophy , psychiatry , and clinical psychology. Today’s consensus—that individual differences result from a combination of inherited and non-genetic factors—strikes a more nuanced middle path between nature- or nurture-focused extremes.

The debate about nature and nurture has roots that stretch back at least thousands of years, to Ancient Greek theorizing about the causes of personality. During the modern era, theories emphasizing the role of either learning and experience or biological nature have risen and fallen in prominence—with genetics gaining increasing acknowledgment as an important (though not exclusive) influence on individual differences in the later 20th century and beyond.

“Nature versus nurture” was used by English scientist Francis Galton. In 1874, he published the book English Men of Science: Their Nature and Nurture , arguing that inherited factors were responsible for intelligence and other characteristics.

Genetic determinism emphasizes the importance of an individual’s nature in development. It is the view that genetics is largely or totally responsible for an individual’s psychological characteristics and behavior. The term “biological determinism” is often used synonymously.

The blank slate (or “tabula rasa”) view of the mind emphasizes the importance of nurture and the environment. Notably described by English philosopher John Locke in the 1600s, it proposed that individuals are born with a mind like an unmarked chalkboard and that its contents are based on experience and learning. In the 20th century, major branches of psychology proposed a primary role for nurture and experience , rather than nature, in development, including Freudian psychoanalysis and behaviorism.

Modern scientific methods have allowed researchers to advance further in understanding the complex relationships between genetics, life experience, and psychological characteristics, including mental health conditions and personality traits. Overall, the findings of contemporary studies underscore that with some exceptions—such as rare diseases caused by mutations in a single gene—no one factor, genetic or environmental, solely determines how a characteristic develops.

Scientists use multiple approaches to estimate how important genetics are for any given trait, but one of the most influential is the twin study. While identical (or monozygotic) twins share the same genetic code, fraternal (or dizygotic) twins share about 50 percent of the same genes, like typical siblings. Scientists are able to estimate the degree to which the variation in a particular trait, like extraversion , is explained by genetics in part by analyzing how similar identical twins are on that trait, compared to fraternal twins. ( These studies do have limitations, and estimates based on one population may not closely reflect all other populations.) 

It’s hard to call either “nature” or “nurture,” genes or the environment, more important to human psychology. The impact of one set of factors or the other depends on the characteristic, with some being more strongly related to one’s genes —for instance, autism appears to be more heritable than depression . But in general, psychological traits are shaped by a balance of interacting genetic and non-genetic influences.

Both genes and environmental factors can contribute to a person developing mental illness. Research finds that a major part of the variation in the risk for psychiatric conditions such as autism spectrum disorder, anxiety disorders, depression, and schizophrenia can be attributed to genetic differences. But not all of that risk is genetic, and life experiences, such as early-life abuse or neglect, may also affect risk of mental illness (and some individuals, based on their genetics, are likely more susceptible to environmental effects than others).

Like other psychological characteristics, personality is partly heritable. Research suggests less than half of the difference between people on measures of personality traits can be attributed to genes (one recent overall estimate is 40 percent). Non-genetic factors appear to be responsible for an equal or greater portion of personality differences between individuals. Some theorize that the social roles people adopt and invest in as they mature are among the more important non-genetic factors in personality development.

Shakespeare was gifted with the ability to reveal, on stage, his characters' hidden thoughts, feelings and motivations. He was a psychologist of sorts.

Personal Perspective: Nature may not have the power to erase childhood trauma, but it can offer a dose of comfort and nurturing to counteract its effects.

Is misophonia neurological or behavioral? Genetic or learned? Understanding misophonia defies binary thinking. Learn how to apply both/and thinking to conceptualize misophonia.

Genes, microtubules, early development.

A Personal Perspective: Facing the interplay between genetic factors and linguistic development prompted a question: Should I trust my instincts or those of others?

The latest findings on genetics reveals how genes may affect the risk for substance use disorders, and how they can help predict which treatment will work.

How do we make sense of new experiences? Ultimately, it's about how we categorize them—which we often do by "lumping" or "splitting" them.

How are twin studies used to answer questions related to the nature-and-nurture debate?

All I ask of strangers in the store—don't judge me as being less competent because my hair is grey and my skin well-textured. I’m just out doing my best, as we all are.

The new Biophilia Reactivity Hypothesis argues our attraction to the natural world is not an instinct but a measurable temperament trait.

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August 6, 2018

What three identical strangers reveals about nature and nurture.

• The new documentary, Three Identical Strangers clearly conveys how it never serves anyone well to unnecessarily mess with nature. Tweet This
• Three Identical Strangers quickly shifts to a real-life Truman Show-type train wreck about three lives that were blindly orchestrated for the purposes of social experiments. Tweet This

Spoiler Alert: The following article includes plot elements from the documentary, Three Identical Strangers .

The recently released documentary, Three Identical Strangers , tells a story that’s at times humorous, at times incredible, and at other times foreboding. The film, directed by Tim Wardle and released across the United States in the past few weeks, tells a story some might remember from headlines in the 1980s: Three college-aged identical triplets—Eddy Galland, David Kellman, and Robert Shafran—each put up for adoption, learn they were separated at birth and are reunited.

It is almost too good to be true. At the time, it was the kind of good news  everyone wants to hear. Seeing the three hardy boys together, whether in New York Pos t photos , on prime-time TV shows, or in person at the Manhattan restaurant they ended up opening, was deeply heart-warming. Everyone wants to belong to a tribe; one can only imagine how powerful it must feel to find two other people who are immediate family; who have ties to you from before you knew; who literally reflect your likeness on their faces; and, who can give you a bear-hug as warm as your own, which you can all but imagine if you’ve ever seen photos of Eddy, David, and Bob together.

It’s a story of the power of nature and nurture. But it’s a story that quickly turns dark when one looks past the lighthearted headlines and comedic banter of TV show hosts, who note how the trio happens to like the same brand of cigarettes. Deeper questions beg to be asked, even if at first by the adopted parents: Why were these boys separated at birth ; why weren’t they informed they had biological siblings ; and why weren’t any of the adoptive parents informed and given the option to adopt all three?

The answers are worse than we might imagine. As the film details, the Louise Wise Adoption Agency , a prominent child-placement agency for Jewish families, intentionally separated a number of twins and multiple-birth siblings and placed them in homes of different socio-economic levels for the purposes of using the children’s lives for research. Quickly, the movie turns from a humorous run of interviews about how they first met, to a real-life Truman Show-type train wreck about three lives that were blindly orchestrated for the purposes of others’ social experiments.

As the film explains, a psychiatrist and psychoanalyst named Dr. Peter B. Neubauer wanted to solve the mystery of nature vs. nurture and decided to use children put up for adoption as guinea pigs for his research. Telling adoptive parents only that they were doing research on adopted children, not on biological siblings separated at birth, the Louise Wise agency facilitated years of research on Eddy, David, and Bob, by sending researchers on house visits. For more than 15 years, they performed psychological testing and took extensive notes and video recordings of the children.

What were the findings of the research? Much is unknown, since the conclusions were never published, and the notes were under seal until 2066. It wasn’t until the documentary filmmakers’ put the pressure on that the Yale officials now holding the research authorized limited access of the psychological files to the studied children who requested access. A number of children have still not been informed they were separated at birth from siblings and studied as a part of the multiple-birth-child research.

It is terrifying to imagine that pivotal aspects of one’s life would be kept secret from them and that their lives would be treated like those of “lab rats,” as one of the brothers described it in the movie. “This is like Nazi sh*t,” another said, who, as a man of Jewish descent, did not choose those words lightly. One family member of one of the boy’s adopted families later said, “coming from the Holocaust, our family has a knowledge that when you play with humans... [things turn out] very wrong.”

Natasha Josephowitz, a former research assistant for Dr. Neubauer, told filmmakers that at the time when the research was being done in the ‘80s, it “did not seem to be bad… it was a very exciting time.” Later in the documentary, however, Josephowitz’s words betrayed an underlying sense that it was unethical. Considering the children out there who still don’t know their origins, the former assistant exclaimed, “these people don’t know they were used this way; they will be so upset!” It was for this reason, however, that Josephowitz seemed comfortable with the idea of keeping the truth hidden instead of bringing it into the open.

Three Identical Strangers offers an empathic view of multiple perspectives throughout the film, but the most salient are those that caution viewers away from intentionally and unnecessarily dividing biological family members.

The Persistent Tension Between Nature and Nurture

In terms of healthy child development, Three Identical Strangers  offers a number of insights. First, treating children like specimens is a dangerous business and will set them on a challenging life course. This says less about adoption as a general practice—since research like Neubauer’s is fringe and rare—and more about the practices of intentional family fragmentation at large.

Watching the brothers describe their trauma growing up reminded me of Alana Newman’s project, Anonymous Us —an online forum and subsequent books where children conceived with reproductive technologies could anonymously open up about their traumatic experiences growing up with their origins unclear. There, individuals could discuss the hardships of being intentionally separated from biological family members, such as a father they’d never meet if they were donor-conceived, or a surrogate mother they’d never meet if they were hired by a gay couple, for instance. One need only  scroll through some of the testimonies  to be struck by the common chords.

Messing with nature affected the boys in similar ways as well. The children had identical looks, similar ways of talking, and common ideas about how to have fun together. Sadly, they also had similar struggles with mental illness growing up: all three displayed separation anxiety, banging their heads against the bars of their cribs; all three experienced depression at times, and all three made visits to psychiatric hospitals as teenagers.

The children’s mental-health challenges from being separated point toward the stubborn truth of how biological families are best kept together when possible. Even if their birth mother wasn’t able to take care of them, the boys could have been put up for adoption together as a trio, which would have reduced some of their nature-disrupted challenges.

But the children’s experiences in different families also revealed something most parents know to be true—that parenting styles make a difference. This message came through the triplets’ entwined stories as a tragic turn of events unfolded.

As a part of the experimentation, Louise Wise Services placed the three children in homes within a 100-mile radius of each other in families with a mom, dad, and older sister who had also previously been placed by the same adoption agency. More than factors like income level, the film suggests that the dynamics of a father’s warmth in the home in particular is a key player in the nurture that affected the three boys the most.

David was placed in an upper-class family with a doctor as his adoptive father; he experienced a rather reserved home life where his father was often unavailable. On the opposite end of the spectrum, Bob was placed in a working-class home with a grocery-store owner as a father who had a very warm and jovial disposition and later became affectionately called the Yiddish nickname “Bubula” by all three boys. Meanwhile, Eddy was placed in a middle-class family with a dad he often clashed with. A person close to the triplets said in the film, Eddy’s relationship with his dad “couldn’t have been good...otherwise, we would have seen him, or Eddy would have talked about him.”

As the brothers grew up, got married, and pursued their business endeavors, some coped better than others with the inevitable stressors in life that come up. After one of the brothers left their joint restaurant business, Eddy’s behavior became erratic and unpredictable, and he displayed manic-depressive symptoms. After receiving brief psychiatric care, he returned home. One morning, when he didn’t show up at work, a family member went to check the house and discovered that Eddy had shot himself. He was 33 years old.

After the tragedy, the surviving brothers couldn’t help but see differences in how they were raised and how it may have affected their life choices. The elderly father of Eddy even said, still in grief, “I often wondered if I didn’t teach him something…how to live life or something…that bothers me.”

Three Identical Strangers offers an empathic view of multiple perspectives throughout the film, but the most salient are those that caution viewers away from intentionally and unnecessarily dividing biological family members. The story clearly conveys how it never serves anyone well to unnecessarily mess with nature.

The plot somewhat twists at the end to emphasize the greater impact of nurture than nature, especially in shaping the boys’ abilities to cope with hardships. One interviewee notes toward the end of the film, “both [nature and nurture] matter; but I think nurture can overcome anything.” Still, at the end of the documentary, the clear villain is not Eddy’s reserved father but the people responsible for separating the triplets at birth, which would seem to suggest that messing with nature has a greater effect. Alas, in this case, the adoption agency is guilty of crimes against both nature and nurture, since they failed to live up to their most fundamental and trusted responsibility—to help provide vulnerable children with as nurturing an environment as possible. Needless separation from blood relatives, years of psychological testing the reasons for which were not disclosed—these also played into the nurture  the boys experienced.

Perhaps that’s why the researchers never penned conclusions from the unethical study. Had they undertaken this task, which would have involved attempting to measure the effects of nature and nurture, they might have had to face how, for the numerous lives involved in their experiment, they actively damaged both.

Mary Rose Somarriba, who completed a 2012 Robert Novak Fellowship on the connections between pornography and sex trafficking, is a writer living in Cleveland and the editor of Natural Womanhood .

* Photo credit: Courtesy of NEON

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What is nature vs nurture (a definition), video: nature vs nurture | genetics | biology .

Examples of Nature vs Nurture

History of nature vs nurture.

Nature vs Nurture Debate and Controversy

Is nature or nurture more important, how does nature vs nurture affect human development.

How Does Nature vs Nurture Affect Personality?

How does nature vs nurture affect mental illness.

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Final Thoughts on Nature vs Nurture

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• Black, S. E., Devereux, P. J., Lundborg, P., & Majlesi, K. (2020). Poor little rich kids? The role of nature versus nurture in wealth and other economic outcomes and behaviors . The Review of Economic Studies, 87(4), 1683-1725.
• Boomsma, D., Busjahn, A., & Peltonen, L. (2002). Classical twin studies and beyond . Nature Reviews Genetics, 3, 872–882.
• Bouchard, T. J., Lykken, D. T., McGue, M., Segal, N. L., & Tellegen, A. (1990). Sources of human psychological differences: The Minnesota Study of Twins Reared Apart . Science, 250, 223–228.
• Eysenck, H. J. (1980). The biosocial nature of man . Journal of Social and Biological Structures, 3(2), 125–134.
• Galton, F. (1865). Hereditary talent and character . Macmillan's Magazine, 12(157-166), 318-327.
• Galton, F. (1874). English men of science, their nature and their nurture . London: Macmillan & co.
• Gelman, R. (2000). Domain specificity and variability in cognitive development . Child Development, 71(4), 854-856.
• Haque, F. N., Gottesman, I. I., & Wong, A. H. (2009, May). Not really identical: epigenetic differences in monozygotic twins and implications for twin studies in psychiatry . In American Journal of Medical Genetics Part C: Seminars in Medical Genetics (Vol. 151, No. 2, pp. 136-141). Hoboken: Wiley.
• Kendler, K. S., Gardner, C. O., Gatz, M., & Pedersen, N. L. (2007). T he sources of co-morbidity between major depression and generalized anxiety disorder in a Swedish national twin sample . Psychological Medicine, 37(3), 453–462.
• Matison, A., Thalamuthu, A., Reppermund, S., Flood, V., Trollor, J., Wright, M., ... & Mather, K. (2022). Nature versus nurture–studying the relationships between diet and depression in older adults . Current Developments in Nutrition, 6(S1), 1118.
• Miller, G. W., & Jones, D. P. (2014). The nature of nurture: refining the definition of the exposome . Toxicological Sciences, 137(1), 1-2.
• Morehouse, A. T., Graves, T. A., Mikle, N., & Boyce, M. S. (2016). Nature vs. nurture: evidence for social learning of conflict behavior in grizzly bears . PLoS One, 11(11), e0165425.
• Plomin, R. E., DeFries, J. C., Craig, I. W., & McGuffin, P. E. (Eds.) (2003). Behavioral genetics in the postgenomic era . American Psychological Association.
• Robinson, G. E. (2004). Beyond nature and nurture . Science, 304(5669), 397-399.
• Singer, P. (1999). A Darwinian left: Politics, evolution and cooperation . New Haven, CT: Yale University Press.
• Stiles, J. (2011). Brain development and the nature versus nurture debate . Progress in Brain Research, 189, 3-22.
• Traynor, B. J., & Singleton, A. B. (2010). Nature versus nurture: death of a dogma, and the road ahead . Neuron, 68(2), 196-200.
• Uher, R. (2014). Gene–environment interactions in severe mental illness . Frontiers in Psychiatry, 5, 48.
• Wermter, A. K., Laucht, M., Schimmelmann, B. G., Banaschweski, T., Sonuga-Barke, E. J., Rietschel, M., & Becker, K. (2010). From nature versus nurture, via nature and nurture, to gene x environment interaction in mental disorders . European Child & Adolescent Psychiatry, 19, 199-210.
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Nature vs Nurture Examples: Genes or Environment

Categories Development

The nature versus nurture debate focuses on the question of whether genetic or environmental factors matter most in the course of human development.

What is it that makes you who you are? Some might say that it is your genes that have the greatest influence in controlling your personality and preferences. Others might say that it is your environment and the unique experiences you have had over the course of your life that have a greater role.

In this article, learn more about the nature vs. nurture debate and what research has found about the contributions of genetic and environmental factors.

Table of Contents

What Is the Nature vs Nurture Debate?

The nature vs. nurture debate is often described as one of the big philosophical and scientific questions facing psychologists. So what exactly does this debate mean? Why is it important for understanding the human mind and behavior?  

Let’s start by learning more about each of these factors.

• Nature: This side of the debate argues that genes have the greatest influence over who we are, from the way we look to the way we behave. Genes determine physical traits such as height, eye color, hair color, and face shape, but they can also contribute to other attributes such as your personality traits and cognitive abilities.
• Nurture: This side of the debate argues that environmental variables such as upbringing, individual experiences, and other social relationships play a more important role. Your upbringing, early social interactions, school, and peers all shape who you are and how you behave.

Let’s consider an example. If a student excels at math, is it because they inherited that ability from their parents or because they work hard to learn the subject?

Nature would suggest that they do well because they are genetically inclined to do so, while nature argues that their talent stems from their upbringing and educational background.

History of Nature vs. Nurture

The debate over nature and nurture predates psychology and goes back to the days of the ancient philosophers. In philosophy, this is often referred to as the nativism versus empiricism debate. What do these terms mean and how do they relate to nature and nurture?

The nativist approach suggests that inheritance plays the greatest role in determining characteristics. Nativism proposes that people’s characteristics, both physical and mental, are innate. These are things that are passed down genetically from our ancestors. The nativist approach essentially espouses the nature side of the argument.

Noam Chomsky’s theory of language acquisition is one of the best-known examples of nativism in psychology.  Chomsky suggested that language develops as a result of an innate language acquisition device. He believed that people are able to learn language because they have an innate, hard-wired capacity for what he referred to as universal grammar.

Empiricism represents the nurture side of the debate. The empiricist approach suggests that all learning is the result of experience and environmental factors.

The philosopher John Locke took an empiricist approach and proposed a concept known as tabula rasa, which means “blank slate.” This approach that the mind is essentially that —a blank slate—and that it is through learning and experience that all knowledge, skill, and behavioral patterns are acquired.

Behaviorism is one example of an empirical approach to understanding human behavior. Behaviorists such as John B. Watson and B.F. Skinner believed that all human behavior was the result of conditioning, either classical (associative) or operant ( reinforcement and punishment ).

Watson was famously known for proclaiming that he could train anyone to be anything using the principles of conditioning, regardless of that individual’s genetics and background.

Approaches to Psychology

While few contemporary psychologists take an extreme, hard-lined empiricist or nativist approach, different branches of psychology do sometimes tend to emphasize one influence over the other.

Biological Psychology

Biological psychology, for example, tends to focus more on the nature side of the debate. This area of psychology focuses on how biological factors influence human behavior, so things such as the brain, neurons, and neurotransmitters are of greater interest than external factors.

Behavioral Psychology

Behavioral psychology tends to take the nurture side of the debate, focusing on how environmental factors and learned associations contribute to how people think and act.

Health Psychology

Health psychology is an example of an approach that tends to lie somewhere in the middle. Health psychologists are focused on understanding how both biological and environmental factors contribute and interact to affect an individual’s health.

Nature vs. Nurture Examples

Looking at examples can be helpful to understand why the nature vs nurture debate has been so crucial throughout psychology’s history. The topic is not just an important philosophical debate. It has been critical for understanding what factors influence different aspects of human behavior and has been the source of considerable controversy at times.

Consider the long debate over the factors that influence intelligence. Those on the nature side of the debate suggest that the greatest influence on IQ is inheritance. Some early thinkers such as Francis Galton believed that intelligence could largely be attributed to genetic factors.

Such views have been used to justify discriminatory social policies and attitudes. When some research suggested that some groups of people had lower IQ scores, for example, some researchers interpreted these results to suggest that these individuals scored lower as a result of genetics.

Those taking the nurture side of the debate point out that other factors, including biased test construction, racism, and systemic discrimination impacting educational access and quality, play a more important role.

Inequality, discrimination, and lack of access play a role in shaping how well people perform on intelligence tests and other assessments of educational outcomes.

Gender Differences and Education

Sex differences in school performance and attainment is another area where the debate between the contributions of nature vs nurture comes into play. Girls often perform better on verbal tests but less well on math. As they advance in school, girls also become less likely to enter STEM courses and STEM fields.

Those taking a nature perspective might suggest that girls are inherently less capable in these subjects. Nature advocates, however, would point out that social variables, including gender stereotypes and discrimination, have a greater influence.

Many researchers today believe that human behavior is influenced by both nature and nurture, and that it is often the interaction of the two variables that is even more important.

Examples of the Impact of the Nature and Nurture Debate

Few modern psychologists would take an extreme nature or nurture position. Rather than asking which one controls specific variables, researchers are more likely to wonder about the degree to which each of these forces plays a role. So what exactly are the relative contributions of nature and nurture?

According to the research, the answer is about 50/50. Researchers collected the results of nearly every twin study conducted over the last half-century. Doing this allowed them to determine which factors played a role in determining certain characteristics.

Twin studies examine similarities and differences by looking at twins who are either raised together or raised apart. This allows researchers to determine the impact of genes versus the environment.

Researchers analyzed more than 2,700 twin studies involving a whopping 14.5 million pairs of twins from 39 different countries and discovered that genes and environment share a roughly equal role in determining who we are.

Variations in personality traits and disease were determined to be 49% due to genetics and 51% due to environment.

One important thing to note is that while the research suggests a 50/50 split, the findings did reveal that genes do play a greater role in the risk of certain diseases. Bipolar disorder, for example, was found to be approximately 70% heritable.

Examples of How Nature and Nurture Interact

Today, many experts suggest that we should be more concerned with how nature and nurture interact to determine how we develop. For example, we might be genetically inclined toward a certain trait, but our experiences can determine to what degree that trait is expressed.

Height is a good example of how genes and the environment can interact to make you who you are. Even if you inherit genes for tallness, proper nourishment is important for reaching that height. Kids who come from tall families might not become tall if they do not receive proper nutrition during their childhood.

So while we know that both factors are equally important, the question we are left to ponder is just how much of a role each factor plays in the development of certain characteristics. As the research suggests, some diseases are more strongly linked to genetics than to the environment.

As researchers continue to explore how nature and nurture interact, we will continue to gain a deeper understanding of the factors that contribute to who we are.

Haworth CM, Davis OS, Plomin R. Twins Early Development Study (TEDS): a genetically sensitive investigation of cognitive and behavioral development from childhood to young adulthood .  Twin Res Hum Genet . 2013;16(1):117-125. doi:10.1017/thg.2012.91

Institute of Medicine (US) Forum on Neuroscience and Nervous System Disorders. From Molecules to Minds: Challenges for the 21st Century: Workshop Summary. Washington (DC): National Academies Press (US); 2008. Grand challenge: Nature versus nurture: How does the interplay of biology and experience shape our brains and make us who we are ? https://www.ncbi.nlm.nih.gov/books/NBK50991/

Sravanti L. (2017). Nurture the nature .  Indian journal of psychiatry ,  59 (3), 385. https://doi.org/10.4103/psychiatry.IndianJPsychiatry_341_17

Nature vs. Nurture Debate: What Really Matters in Psychology

Is your life and personality shaped by your genes or environment? This is the big question of the nature vs. nurture debate, science has the answer.

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Are you simply a product of your environment, or do your genes have the final say? This is the ultimate question of the nature vs. nurture debate. Take a deep dive into the origins of the debate, and learn how epigenetics has upended the argument once and for all.

What is Nature vs. Nurture?

Nature vs. nurture can be defined as the difference between the genetics that people inherit (nature) vs. the environmental influences that accumulate over a lifetime (nurture). For years, many people have believed that nature rules supreme and reject the idea that environment or parenting has a large role in shaping people. 

The big question in the debate is this––how much of a person’s personality is a result of genes, and how much is related to environment and experiences? People have been arguing about this for years for political, personal, and social reasons. 

So, what’s the answer…are we shaped by nature or nurture? The answer is both, and it depends on which traits. Read on for the science of nature or nurture below.

Examples of Nature vs. Nurture

Let’s look at some examples to see how nature and nurture impact a person’s development. 

Examples of Nature Impacting Human Development:

• Genetically predisposed to be tall.
• Inherited red hair and blue eyes from the maternal side of the family.
• ADHD, when it appears together with conduct disorder, is attributed to genes 1 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3303131/ .
• Genes contribute to genetic disorders such as Edwards syndrome, Patau syndrome, and Warkany syndrome.
• Anxiety and depression occurring together 1 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3303131/ are considered to be connected to a genetic predisposition.

Examples of Nurture Impacting Human Development:

• The mother experienced high amounts of prenatal stress 2 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9676865/#:~:text=Overall%2C%20maternal%20anxiety%20and%20depression,2017%3B%20Takegata%20et%20al.%2C , contributing to a fearful personality in the child, who is likely to express positive emotions. 
• Lack of healthy attachment to the caregiver impacts relationships with others throughout life.
• Growing up malnourished 3 https://www.frontiersin.org/articles/10.3389/fpsyg.2019.01886/full can stunt height and contribute to obesity.
• A supportive community environment 4 https://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=1583&context=jhdrp contributed to feelings of confidence and the ability to succeed.
• Growing up during political instability causes heightened aggression and revenge-seeking 5 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3712526/#:~:text=There%20is%20now%20convincing%20documentation,disorders%2C%20fear%20and%20panic%2C%20poor later in life. 

How Has Nature vs. Nurture Changed Over Time? 

Nature vs. nurture has changed in many ways, perhaps the most significant change being the understanding of nurture. Early developmentalists saw nurture as the care given to the child by their parents (usually with an emphasis on the mother). Today scientists continue to discover that nurture includes many environmental influences––from prenatal to end-of-life. 

While the nature vs. nurture debate was once hotly disputed, most human developmentalists agree that both nature and nurture have a hand in shaping individuals. 

What you should know: The study of epigenetics 6 https://developingchild.harvard.edu/resources/what-is-epigenetics-and-how-does-it-relate-to-child-development/ has changed the nature vs. nurture debate landscape. Genes are not static but are impacted by nurture (environment), making it possible to change and override gene expression. 

We’ll get to even more examples below, but let’s look at a couple of scenarios of how nurture can impact genes.

Scenario 1: You are genetically predisposed to obesity, but your mom had excellent dietary health during pregnancy; this impacts your epigenome 7 https://ehp.niehs.nih.gov/doi/10.1289/ehp.8700?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed , reducing the risk for obesity and increasing your lifespan. 

Scenario 2: In early childhood, you have several negative experiences that deeply impact you. These experiences have the ability to override your natural gene expression 8 https://www.sciencedirect.com/science/article/abs/pii/S0306452212003028?via%3Dihub and “increase the risk not only for poor physical and mental health outcomes but also for impairments in future learning capacity and behavior.”

Everything from social interactions to diet to air quality can impact how genes interact and are expressed. 

“Contrary to popular belief, the genes inherited from one’s parents do not set a child’s future development in stone.” — Harvard Center on the Developing Child

The question, as we’ll see, isn’t nature or nurture, but rather nature and nurture. 

What Does Nature vs. Nurture Have to Do With Psychology, Sociology, and Genetics?

The nature vs. nurture debate has both been influenced by and has influenced psychology, sociology, and genetics. 

• Psychology is largely concerned with the mind and behavior of the individual.
• Sociology is concerned with the collective experiences and behavior of society.
• Genetics studies how genes and traits are passed down through families. 

Ultimately, all three are concerned with studying how and why people behave the way they do. But this isn’t just about behavior; nature vs. nurture has been extensively studied in relation to the body. Scientists want to know how genes and the environment impact everything from low back pain 9 https://pubmed.ncbi.nlm.nih.gov/23335362/ to obesity 10 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3224976/ . 

Let’s dive deeper so you can decide for yourself how much nature or nurture may have had a hand in shaping your own personality. 

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Who Came Up With Nature vs. Nurture?

Sir Francis Galton is credited with first coining the nature vs. nurture phrase. To better understand the beginning of the nature vs. nurture debate, we have to go back to the 1800s to look at why Galton came up with “nature vs. nurture” in the first place. Hold on because it’s not pretty.

Galton was a particularly unlikable anthropologist who gave us fingerprinting (great!) and invented eugenics (why was he knighted?). 

He sought to defend his beliefs with science and set out to prove that nature, not nurture, determined the intelligence and “excellence” of a person 11 https://galton.org/books/hereditary-genius/ . His cousin, Darwin, gave his stamp of approval on the “capital account” 12 https://galton.org/letters/darwin/correspondence.htm given by Galton in his book, Hereditary Genius 13 https://galton.org/books/hereditary-genius/text/v5/galton-1869-hereditary-genius-v5.htm#_Toc68688332 . 

In the book, Galton used the nature over nurture argument to propose and legitimize the ultimate elimination of criminals, “worthless” individuals, and “inferior” races (including Africans, Australians, Jews, working-class women in London, etc.) by controlling who could procreate and who couldn’t.  

While it’s unfortunate Galton had such a negative impact on science, it provides important context. Understanding where the debate originated helps us understand the ethical implications of how an unbalanced view of nature has been used to justify ongoing injustice both in policymaking and the treatment of individuals. 

Even though the argument for nature had a sordid start, let’s not throw it out completely! There is a lot we can learn about  ourselves, as both nature and nurture have a hand in shaping who we are. 

How Nature and Nurture Impact Human Development & Personality

Most developmentalists believe each person is unique and responds to a situation or experience based on many factors. As you try to understand the impact of nature and nurture on yourself or others, please remember while human development is a refined science, people are not computers. People can, and often do, defy the expectations of science, either becoming more or less resilient in the face of challenges. 

How Nature Impacts Personality

Now remember, nature involves the genetics that impact a person’s development and personality. Studies have found a person’s genes impact 30-60% of personality 14 https://www.nature.com/articles/s41380-018-0263-6 . If this sounds like a broad range, it is! But, we must consider all the variables that interact with a person’s genes. 

• A number of studies 15 https://journals.sagepub.com/doi/10.1111/j.0963-7214.2004.00295.x have found a connection between genetics and emotional well-being. 
• While personality seems to be heritable, to some extent, researchers are still trying to understand the actual “genetic basis of personality 16 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7012279/ .”

What this really means: Researchers would like to attribute personality traits like neuroticism or extroversion to a specific gene in your body, but, at the end of the day, they can’t. Studies have linked genetics with certain behavior and traits, but studies are often difficult to replicate 16 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7012279/ and may have gaps in the research. Nature clearly impacts a person, but science isn’t as hard and fast as some might think. 

Watch our video below to learn what type of personality you have:

How Nurture Impacts Personality

Remember the variables we mentioned that impact nature? Those variables are largely introduced by nurture. Here are some examples of how nurture can impact personality. 

• Maternal stress during pregnancy 17 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5052760/ has been found to increase the child’s stress. This, in turn, impacts the temperament of the child 18 https://srcd.onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-8624.1995.tb00851.x . 
• A study in Germany 19 https://pubmed.ncbi.nlm.nih.gov/22275337/ found that military training decreased agreeableness in personalities, and this change persisted even after a person left the military and re-entered the workforce.  
• Social expectations create the most profound personality changes 20 https://pubmed.ncbi.nlm.nih.gov/21859226/ in the young and the elderly. 
• Food insecurity harmfully impacts mental health 21 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7282962/ , causing everything from anxiety to maternal depression. Interestingly, food insecurity also increases the risk of obesity 3 https://www.frontiersin.org/articles/10.3389/fpsyg.2019.01886/full . 

As you can see, nurture isn’t just how much a mother holds and comforts her baby! This is a limited view of nurture when in reality, there are so many external factors involved. The psychologist Urie Bronfenbrenner identified six key ecological systems that profoundly impact a person. All of these systems are an element of nurture. 

• Microsystem: Immediate social relationships, including family and peers.  
• Exosystem: Local institutions such as school, churches, temples, mosques, etc.
• Macrosystem: The larger setting that a person inhabits, such as culture, economics, and politics, creates a sense of shared beliefs and expectations of behavior. 
• Mesosystem: How other systems are interconnected.
• Chronosystem: The historical context that a person lives in, including values, events, technologies, and birth cohort (e.g., Boomer, Gen X, Millennial, Gen Z).
• Bioecological: The internal biology of a person. 

The ecological systems don’t just impact a person during childhood development. Psychology recognizes that people change through all phases of life! Personality is not set in stone 22 https://pubmed.ncbi.nlm.nih.gov/12757147/ . As a person ages and lives in various environments, this impacts how the person experiences the world around them. 

“In the real world, there is no nature vs. nurture argument, only an infinitely complex and moment-by-moment interaction between genetic and environmental effects” — Gabor Maté, Physician and Author

Can You Change Your Genes? 

At the end of the day, your genes (nature) are directly impacted by your environment (nurture). This means you have the power to change your genes! 

If that doesn’t make sense and you’re still wondering which is more important––nature or nurture, the delightful world of epigenetics has the answers. Let’s start with this beautifully explained infographic from Harvard 6 https://developingchild.harvard.edu/resources/what-is-epigenetics-and-how-does-it-relate-to-child-development/ .

Image: Harvard Center on the Developing Child

Essentially, epigenetics put to rest the old question of whether nature or nurture is more important in shaping identity and personality. Because of how epigenetics work in your body, nature, and nurture have a symbiotic relationship––one impacting the other and creating an ebb and flow in personality. 

You can change your genes by changing your behavior and your environment. 

Pro Tip: Studies have found you can begin to modify your epigenetic patterns 23 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3752894/ when you…

• Adjust your diet
• Add in physical exercise
• Reduce alcohol consumption
• Remove tobacco
• Limit exposure to environmental pollutants
• Learn to manage stress
• Avoid working night shifts 
• Have supportive, safe relationships

How Nature and Nurture Impacted Your Own Development

As you think about how nature and nurture have impacted you, we encourage you to reflect on your experiences both in the past and the present. Think about the experiences of your parents. What was it like for your mom when she was pregnant with you, the environment you grew up in, and where you find yourself today? 

Your life is an intricate story woven with tiny threads of your experiences, the experiences of your environment and community, and the experiences of your ancestors. The past had a hand in shaping the person you are today, but you have the amazing ability to change the direction of who you will become. 

The Highlights:

• Inherited genes may impact things like height, personality, and health.
• Experiences and environment impact how genes are activated and released. This is epigenetics and impacts everything from what triggers you to how you respond in social situations. 
• Safe relationships and supportive environments can positively impact the epigenome. 
• As much as possible, choose to be in positive environments. Surrounding yourself with beauty, clean air, nature, and healthy relationships builds your capacity for change. 

As you identify the areas of your life that you’d like to improve or change, emotional intelligence is an excellent place to start. This is a skill that will help you connect with yourself and others. Check out our article on 10 Emotional Intelligence Traits to Master for Self-Growth .

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21 Nature vs Nurture Examples

Viktoriya Sus (MA)

Viktoriya Sus is an academic writer specializing mainly in economics and business from Ukraine. She holds a Master’s degree in International Business from Lviv National University and has more than 6 years of experience writing for different clients. Viktoriya is passionate about researching the latest trends in economics and business. However, she also loves to explore different topics such as psychology, philosophy, and more.

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This article was peer-reviewed and edited by Chris Drew (PhD). The review process on Helpful Professor involves having a PhD level expert fact check, edit, and contribute to articles. Reviewers ensure all content reflects expert academic consensus and is backed up with reference to academic studies. Dr. Drew has published over 20 academic articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education and holds a PhD in Education from ACU.

The nature vs. nurture debate is the long-standing argument over whether heredity (nature) or environment (nurture) plays a greater role in developing human characteristics and behaviors. 

Nature refers to the biological characteristics we are born with, including genetic predispositions toward certain traits. In contrast, nurture includes external influences that shape us, such as culture, relationships, and everyday experiences.

For example, when it comes to personality development, some people believe that genetics play a stronger role than environmental factors; this would be considered a nature-focused perspective. 

Others may view the environment as more important. In this case, a nurturing upbringing could help individuals develop their personalities. Therefore, both sides can have valid arguments for their respective positions in the debate.

The Nature Perspective

In the context of the nature vs. nurture debate, nature refers to biological heredity and genetic predispositions inherited by individuals from their parents at birth. 

Buheji (2018) states that:

“in the “nature vs. nurture” debate, nature refers to an individual’s innate qualities (nativism)” (p. 221).

This includes physical characteristics such as eye color, facial features, personality traits, and behavioral tendencies.

Genes determine the unique physical characteristics of each individual while also influencing psychological and social behavior.

Some research implies that roughly 50% of an individual’s personality and disposition are pre-determined by genetics (Bouchard & Loehlin, 2001).

However, Krueger and colleagues (2008) state that the interplay between gene-environment interactions has a consequential effect on one’s character traits. Hence, the heritability of personality isn’t always precisely 50%.

So, nature is the hereditary and genetic characteristics pre-determined at birth and influence a person’s behavior.

The Nurture Perspective

Nurture, in the context of the nature vs. nurture debate, is used to describe environmental factors that influence an individual’s development. 

According to Coon and Mitterer (2014), nurture:

“…refers to the sum of all external conditions that affect a person” (p. 100).

This includes a variety of influences such as parenting style, educational experiences, cultural background, and exposure to different environmental conditions over time.

While “nurture” may naturally invoke ideas of childhood and parental care, environmental components and life experience can shape human mental, emotional, and physical health throughout their lives (Harsha et al., 2020).

For example, lifestyle choices have been found to impact a person’s risk for developing certain diseases and their level of immunity against illness. 

Furthermore, addiction susceptibility can be impacted by environmental factors such as peer group that has been observed throughout an individual’s life (Ducci & Goldman, 2012).

Simply, nurture is an umbrella term for any environmental influences that shape the development of a person’s mental, physical, and emotional health. 

Examples of Nature vs Nurture

Nature examples.

• Eye color : A person’s eye color is determined by their genetic makeup and inherited from their parents.
• Height : As with eye color, height is a physical trait that is determined by a person’s genes and largely determines an individual’s adult height.
• Risk of D iseases : A person’s risk for developing certain diseases can be partially attributed to their genetic predisposition for that illness and influenced by lifestyle factors and personal environment.
• Immune S ystem F unctionality : Genetic predisposition plays an important role in determining an individual’s resistance to disease through the strength of their immune system. However, lifestyle choices can also influence this trait over time (e.g., diet and exercise).
• Hair Color: Hair color is determined by genetic factors. Recessive genes, like the red hair gene, generally have to be present in both parents for the recessive gene to become dominant.
• Balding: Going bald is an inherited trait. Some groups – such as male British Anglo-Saxons – are more likely to go bald in their 30s than the average.
• Adrenaline response : An individual’s ability to react quickly in dangerous situations—their “fight or flight” response—tends to be innate in all of us.

Nurture Examples

• Ethics and Parenting style : An individual’s upbringing and the parenting style they are exposed to can shape their behavior, emotional reactions, and psychological outlook throughout life.
• Linguistic Determinism Theory : In this theory, the language we are taught as a child will determine the ways we think and interact with the world. It goes some way to explaining how people of differing language groups may have differing values and belief systems .
• Values and Cultural background : Depending on their cultural background, different individuals may be exposed to different values and belief systems, which can impact their attitudes toward certain issues or topics/ideas/beliefs.
• Anxiety and Exposure to T rauma : Experiences with violence or traumatic events can have long-term effects on an individual’s psychology which could manifest outwardly as symptoms of anxiety or difficulty coping under pressure in later stages of life.
• Positivity and Social E nvironment : The people an individual interacts with can either positively or negatively affect their development. Individuals need to surround themselves with positive influences while avoiding those that might lead them down the wrong path in life.
• Relationship E xperiences and Sense of Security : Positive relationships throughout a person’s life will tend to improve outlook and well-being. In contrast, unhealthy relationships could leave long-term psychological damage that might need professional help before it can be addressed adequately by an individual suffering firsthand.

Nature and Nurture Examples

• Personality traits: The role of genetics (nature) in determining personality traits, such as extraversion or conscientiousness is balanced against the influence of upbringing and life experiences (nurture).
• Aggression: There is debate over whether aggressive behavior is primarily influenced by genetic factors (nature) or by environmental factors, such as upbringing, social learning , and exposure to violence (nurture).
• Athletic ability: The role of genetics (nature) determines a lot of our natural talent in sports but the importance of training, motivation, and exposure to physical activity (nurture) takes us the rest of the way.
• Musical talent: Musical ability may be affected by genetic predisposition (nature) but also environmental factors, such as exposure to music at a young age, education, and practice (nurture).
• Attachment styles: It is debatable whether a person’s attachment style (secure, anxious, or avoidant) is impacted by genetics (nature) versus the influence of early childhood experiences and caregiver relationships (nurture).
• Empathy and emotional intelligence: The capacity for empathy and emotional intelligence is debatably determined by both genetics (nature) and the result of upbringing, social exposure, and life experiences (nurture).
• Spiritual beliefs: Theological determinism holds that god has pre-selected his chosen people who will be true believers (nature) while others think that belief in god is a choice and we must raise our children to maintain a belief in god (nurture).
• Learning styles: In the 1980s, there was extensive debate over whether preferred learning styles, such as visual, auditory, or kinesthetic, are determined by genetic factors (nature) or influenced by educational experiences and personal development (nurture). Today, most education theorists believe that learning preferences are based on nurture over nature.
• Addiction susceptibility : Scientists have identified genes related to addiction susceptibility, even though this trait is also heavily influenced by the environment (Ducci & Goldman, 2012).
• Intelligence : Education can significantly impact traits such as intelligence levels and knowledge base, with certain experiences inspiring curiosity or creativity in individuals later in life.

Origins of Nature vs. Nurture Debate

The debate surrounding the extent to which human development is influenced by nature (heredity) or nurture (environmental factors) has been around since ancient times.

Plato, the renowned Greek philosopher, argued that beneficial traits in humans were attributable to both nature and nurture. He believed people could adapt to external occurrences throughout their lifetime (Englander, 2010).

However, his mentor Socrates leaned more towards genetics as the primary factor of human development – a notion known as Nativism, which was coined by both philosophers together.

In the late 1800s, Charles Darwin’s theory of evolution and Sir Francis Galton’s article “Hereditary Talent and Character” sparked a resurgence in interest in this topic (Galton, 1865)

So, Galton (1865) suggested hereditary influences to be at least as important as the environment when determining an individual’s outcomes in life.

The debate continued through subsequent decades, with psychologist John B. Watson’s revolutionary suggestion that environment—what he called “nurture”—was more important than hereditary factors or biology (Herrnstein, 1998).

In recent years, researchers have realized that both internal (genetic) and external (environmental) factors play a role in how individuals develop physically and psychologically. 

As such, most experts now subscribe to an approach that looks at how both genetic inheritance and environmental influences work together throughout life to shape each person’s unique character traits and behaviors.

The Role of Epigenetics in the Nature vs. Nurture Debate

Epigenetics is the study of changes in gene expression caused by environmental factors, such as diet and exposure to toxins, without altering the underlying sequences of DNA .

It is an emerging field of research that has been gaining prominence in recent years as scientists try to uncover how and to what extent the environment can shape genetic expression (Harvard University, 2019).

Epigenetic influences are now considered a significant factor in the nature vs. nurture debate, particularly in how individuals develop physically and psychologically throughout life. 

Evidence suggests that epigenetic mechanisms can be used to modulate gene expression depending on the environment, thus having a direct influence on an individual’s characteristics and behaviors (Harvard University, 2019).

This means that while both genetics and environment may play a role in determining an individual’s outcomes in life, epigenetics provides an additional layer of complexity by allowing environmental factors to interact with gene expression.

Nature vs. nurture is a decades-old debate that continues to be studied in various fields. 

Nativists state that genetics play a major role in determining characteristics and behaviors. For example, a person may have inherited certain traits from their family. 

However, empiricists suggest that external factors, such as upbringing and lifestyle choices, can also have a significant influence.

From ancient philosophers to modern-day scientists, this debate has gone through various iterations and continues to evolve today with the introduction of epigenetics. 

More recently, epigenetics have emerged as a key factor in the debate. Its  mechanisms can be used to modulate gene expression depending on the environment, thus having a direct influence on an individual.

So, it appears that both nature and nurture are important factors in determining an individual’s outcomes in life. 

Bouchard, T. J., & Loehlin, J. C. (2001). Genes, evolution, and personality.  Behavior Genetics ,  31 (3), 243–273. https://doi.org/10.1023/a:1012294324713

Buheji, M. (2018).  Understanding the power of resilience economy . Mohamed Buheji.

Coon, D., & Mitterer, J. O. (2014).  Psychology: A journey . Wadsworth/Cengage Learning.

Ducci, F., & Goldman, D. (2012). The genetic basis of addictive disorders.  Psychiatric Clinics of North America ,  35 (2), 495–519. https://doi.org/10.1016/j.psc.2012.03.010

Englander, M. (2010).  The nature and nurture of learners . AuthorHouse.

Galton, F. (1865).  Hereditary talent and character . University of Bristol Library.

Harsha, N., Ziq, L., Lynch, M. A., & Giacaman, R. (2020). Assessment of parental nurturing and associated social, economic, and political factors among children in the West Bank of the occupied Palestinian territory.  BMC Pediatrics ,  20 (1). https://doi.org/10.1186/s12887-020-02317-0

Harvard University. (2019).  What is epigenetics? The answer to the nature vs. nurture debate . Center on the Developing Child at Harvard University; Harvard University. https://developingchild.harvard.edu/resources/what-is-epigenetics-and-how-does-it-relate-to-child-development/

Herrnstein, R. J. (1998). Nature as nurture: Behaviorism and the instinct doctrine.  Behavior and Philosophy ,  26 (1/2), 73–107. https://www.jstor.org/stable/27759383

Krueger, R. F., South, S., Johnson, W., & Iacono, W. (2008). The heritability of personality is not always 50%: Gene-environment interactions and correlations between personality and parenting.  Journal of Personality ,  76 (6), 1485–1522. https://doi.org/10.1111/j.1467-6494.2008.00529.x

• Viktoriya Sus (MA) #molongui-disabled-link Cognitive Dissonance Theory: Examples and Definition
• Viktoriya Sus (MA) #molongui-disabled-link 15 Free Enterprise Examples
• Viktoriya Sus (MA) #molongui-disabled-link 21 Sunk Costs Examples (The Fallacy Explained)
• Viktoriya Sus (MA) #molongui-disabled-link Price Floor: 15 Examples & Definition

• Chris Drew (PhD) https://helpfulprofessor.com/author/chris-drew-phd-2/ 23 Achieved Status Examples
• Chris Drew (PhD) https://helpfulprofessor.com/author/chris-drew-phd-2/ 15 Ableism Examples
• Chris Drew (PhD) https://helpfulprofessor.com/author/chris-drew-phd-2/ 25 Defense Mechanisms Examples
• Chris Drew (PhD) https://helpfulprofessor.com/author/chris-drew-phd-2/ 15 Theory of Planned Behavior Examples

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At the Lab Episode 21: Nature versus nurture

• autism spectrum disorders
• Gabrielle Pouchelon
• neurodevelopment
• Neuroscience

What makes you, you? We know your genes, your parents’ genes, and their parents’ genes all play a big role. But what about everything else—your individual circumstances and surroundings … your life? This week At the Lab , CSHL Assistant Professor Gabrielle Pouchelon gets at the heart of the matter—in your head.

Read the related story: Finding the sweet spot in brain development

Sam Diamond: You’re now At the Lab with Cold Spring Harbor Laboratory. My name is Sam Diamond and this week At the Lab , “Nature versus nurture.”

SD: It’s one of humanity’s oldest arguments. Are we solely the product of our genetics? Or is it our upbringing and surroundings that determine who we are? Today, we understand that the answer is a bit of both.

SD: What we don’t know is precisely how this works. How do nature, in the form of our individual biological makeup, and nurture, in the form of environmental and experiential factors, interact during our brain’s development?

SD: That question is central to the work of CSHL Assistant Professor Gabrielle Pouchelon. To answer it, she starts with our earliest neural connections.

Gabrielle Pouchelon: In mice, they happen during the first week after birth. So, right after birth, they’re highly connected to their sensory system. And that is also very important because we’re not yet able to create sensorimotor action to integrate the world. But we’re definitely receiving all those sensory inputs.

SD: Pouchelon’s team identified a specific protein that helps regulate the timing of the mouse brain’s early neural connections. Importantly, these connections are temporary and highly dynamic.

SD: That’s critical because it means the brain can adapt to minor mishaps in development without a significant impact. In fact, that’s exactly what Pouchelon’s team observed. When the timing of these connections was altered in mice, the resulting changes were so minute they were hardly detectable.

GP: Indeed, there is no huge defect. They run fine. They explore the same way. And it’s only when we take all of those little behavior sequences and look at them together that we see a difference. So, what we see is nothing that we can interpret as dysfunctional. We can just say that they use their system differently.

SD: Sound familiar? While Pouchelon’s research does not directly connect this atypical behavior with autism, she is willing to speculate that disruptions in the timing of early neural connections could impact how we think and act later in life.

SD: And this speaks to an overarching theme of Pouchelon’s work. Long before we utter our first words, our genetic programming and environmental cues are in regular conversation—nature and nurture talking it out and always listening.

SD: Thank you for listening as we talk out our latest science. If you like what you heard, please subscribe to get another fascinating story like this delivered each week. You can also find more at CSHL.edu. For Cold Spring Harbor Laboratory, I’m Sam Diamond, and I’ll see you next time At the Lab .

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Our pest control is killing the bees

By Harri Weber

Posted on Aug 27, 2024 4:03 PM EDT

3 minute read

New research into the link between bee death and pesticides bolsters calls for alternative pest control methods. According to a peer-reviewed study published in Nature Sustainability by researchers at the University of Southern California Dornsife, wild bee sightings in the U.S. have fallen by as much as 43% in areas with high pesticide use, versus areas where no pesticides are used.

While data is mixed on the status of the more recognizable honeybee, which was brought to the Americas by European colonizers in the 17th century, the decline of native pollinators is evident ; about a quarter of wild bee species are “imperiled and at increasing risk of extinction,” according to a 2017 study by the nonprofit Center for Biological Diversity, which cited habitat loss and pesticide use as the primary threats, along with climate change and urbanization.

To better understand the interaction between pesticides and native bees, the USC researchers analyzed 178,589 observations of 1,081 wild bee species, pulling from museum records, ecological surveys, and community science data, as well as governmental land and county-level pesticide surveys. For wild bees, the researchers found that the “negative effects of pesticides are widespread,” and the rise in use of two common pesticides, neonicotinoid and pyrethroid, “is a major driver of changes in occupancy across hundreds of wild bee species.”

The study points to alternative methods of pest control as a means of protecting the pollinators and the vital role they play in ecosystems and food systems. Such alternatives include mitigating pests with natural predators and using traps and barriers before resorting to pesticides. 

Some research suggests that competition for pollen from honeybees is harmful for native bees, but the new USC study didn’t find a noteworthy connection there, with lead research and USC professor of biological sciences and quantitative and computational biology Laura Melissa Guzman acknowledging that more study is needed to back this up. 

“While our calculations are sophisticated, much of the spatial and temporal data is coarse,” Guzman acknowledged in a university press release. The researcher added, “We plan to refine our analysis and fill in the gaps as much as possible.” 

High pesticide use is harmful for humans, too. The EPA has found that some pesticides—organophosphates and carbamates in particular—can affect the body’s nervous system, while others can impact the endocrine system. Around 1 billion pounds of pesticides are used in the U.S. annually, per a 2017 Ohio-Kentucky-Indiana Water Science Center study. Consumer Reports said in April that it found risky levels of pesticides in 20% of produce in the U.S.

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Nature Nurture Issues and Debates Essay 16 Mark Model Answer AQA Psychology New Spec

Subject: Psychology

Age range: 16+

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23 August 2024

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A grade answer written by a teacher in line with AQA mark schemes, specification and approved textbooks.

AO1 = Nativists, empiricists, tabula rasa, twin studies, interactionism, diathesis stress model

AO3 = Balance of strengths and limitations relating to practical application and societal implications

Approximately one page long to reflect the amount a student can write under exam conditions.

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Issues and Debates Essays AQA Psychology A-Level Bundle

16 mark answers for the entire unit. All answers are based on the AQA specification, mark schemes and textbooks. Answers include AO1 (description) AO2 (application to units studied in the course) and AO3 (evaluation). References to methodological criticisms, issues and debates and practical applications are made where appropriate. All answers are A grade and can be differentiated to meet different abilities. Answers are approximately one page long to reflect the amount a student can write under exam conditions.

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• Published: 27 August 2024

Funerary vs. domestic vessels from the Hallstatt period. A study on ceramic vases from the Milejowice settlement and the Domasław cemetery

• Angelina Rosiak 1 ,
• Anna Józefowska 2 ,
• Joanna Sekulska-Nalewajko 3 ,
• Jarosław Gocławski 3 &
• Joanna Kałużna-Czaplińska 1  

Scientific Reports volume  14 , Article number:  19942 ( 2024 ) Cite this article

Metrics details

• Analytical chemistry

Clay vessels have a wide variety of functions in social activities in the Hallstatt period. In addition to food storage and processing, they were used for ritual purposes and as funerary vessels. The paper presents the results of archaeological and chromatographic studies of 31 vases from two different Hallstatt culture sites in lower Silesia (Poland). The investigations included vessels fragments from the Domasław cemetery and from the Milejowice settlement. The chromatographic analyses focused on fatty acids and biomarkers and made it possible to identify the most likely sources of substances they came into contact with during use. The c-means and hierarchical cluster analyses showed that grave vessels differed from settlement ceramics. Thus, conclusions on the diverse vessel functions could be made.

Introduction

Interpreting the functions and uses of prehistoric ceramic containers is largely intuitive 1 . The particular shapes and technological properties make certain pottery types suitable for specific activities related to drinking, serving, storing, and preparing food and/or beverages. Morphologically, pottery might be divided into vases, pots, bowls, cups and other vessel types. However, the functions this classification implies may differ from their actual use and they may contain completely different products in particular contexts.

The south-western Poland’s Hallstatt period (ca. 8–6th BC) saw deep social transformations, i.e., the emergence of local “elites”—probably due to trade development and intense external contacts. The import influx, the gradual adoption of cultural ideas from the east and the south, and, above all, the population’s growing wealth resulted in lifestyle changes. This transformation might be traced in settlement evidence through new forms of status display and in cemeteries, where the practices of the Hallstatt elites were imitated. The emergence of new pottery types, such as vases with conical rims and funnel-shaped necks, plate-like bowls, and rhyta , was associated with these new patterns and social “needs” during feasting or ceremonies. Unfortunately, neither the daily-use nor offering vessels provides reliable information on their contents or usage patterns. Therefore, by comparing the settlement and funerary contexts of pottery using chromatographic analyses, we sought to identify the functions of these containers and, thus, better understand the ancient practices.

For this purpose, two key sites of the Hallstatt period, located close to each other were selected: a settlement in Milejowice, site 19, partly fenced with palisade-like circular structures and a cemetery in Domasław, sites 10/11/12, with richly furnished chamber graves. These Silesian sites were excavated in 1999–2003 (Milejowice) and 2006–2008 (Domasław) by the Institute of Archeology and Ethnology of the Polish Academy of Sciences in Wrocław.

Buildings at the extensive Milejowice settlement were organised in clusters, with a separated zone surrounded by a regular circular palisade. This part cannot be interpreted as fortifications but rather as the elite’s seat, inhabited by a privileged group displaying their high social and economic status. The site consisted of numerous residential and non-residential ground-level buildings and dug-in structures, such as storage pits, wells, a metallurgy workshop, votive pits and resource pits. Pottery, including the “luxurious” types with painted or graphite-coated surfaces, might also have been manufactured here 2 , 3 , 4 , 5 , 6 .

At the Hallstatt cemetery in Domasław, ca. 800 cremation burials were discovered, including 300 chamber graves with impressively rich personal ornaments, weapons, toiletry sets, tools, bronze vessels, and a large amount of luxurious pottery. The graves contained selected vessel types—for food, drinks and other offerings. They were often exceptionally decorative—painted or with glossy, graphite-coated surfaces, imitating metallic vessels—deposited in a predefined position and number 7 , 8 .

The authors intended to compare the use of vase-shaped vessels in funerary and settlement contexts and from features interpreted as residential, votive or connected to household/production. The main goal was to determine whether it is possible to distinguish between funerary and household pottery considering the products it contained and whether any significant differences indicate the function of these storage vessels in different contexts.

The paper focuses on ceramic vase-like vessels found at the archaeological sites from the Hallstatt period: the Milejowice settlement and the Domasław cemetery. The analyses included 31 vases (16 funerary and 15 settlement finds). The conclusions, however, were based on the results obtained from 120 vessels of various types from these two sites examined as part of the project. Table 1 shows the characteristics of the studied vases.

The vases (Fig.  1 ) are medium and large vessels, with rounded or close to biconical bodies and varying neck shapes. Most of them had funnel-shaped rims and cone-shaped necks. Another type featured conical necks and straight or slightly everted rims, while others had more S-shaped profiles and sometimes handles.

Selected vases from the Domasław cemetery and the Milejowice settlement (S-sample).

Their diameters ranged to over 45 cm at the cemetery and up to 60 cm at the settlement. Vessels with funnel-shaped rims constituted the numerous and characteristic group of vessels. They frequently occurred in Silesia during the Hallstatt period, and their surface treatment and decorations indicated an influence from the Hallstatt zones 9 . Almost all cemetery vases and some from the settlement (46, 47, 58, 61) have graphite-coated surfaces. The upper parts of bodies are often ornamented with slanting, vertical or horizontal grooves or incisions, less often with dimples. Pushed-out or attached conical knobs surrounded by semicircular grooves also occurred, as well as grips, handles, and ribs. On vessel 46, they formed spectacular spiral arrangements. Some vessels are painted. Within the palisade-surrounded area (43, 46, 47, 49), painted ware and vases with funnel-shaped rims and cone-shaped necks were 2–4 times more numerous than in the other settlement clusters 10 .

At the settlement, the studied vases occurred in features interpreted as votive (42, 43, 46), sunken structures of residential or economic character (47, 49, 53, 55, 58, 70, 72, 79, 86), a well (39, 40), a bronze-working workshop (61), and a storage pit (70). In graves, vases were deposited in precisely defined contexts. All occurred in grave chambers except for vessel 90, which was placed outside the chest. Vases with funnel-shaped rims were parts of sets consisting of two vessels of this type located in grave centres. Those with cone-shaped necks were found in the eastern parts (105, 106, 108). Both were part of drinking sets placed in the graves. Vases used as urns were not included in the analysis. They contain a much wider range of compounds, including those of an intoxicating nature.

• Chromatographic analyses

A gas chromatograph (6890N GC System, Agilent Technologies) coupled to a mass spectrometer (MS 5973 Network Mass Selective Detector, Agilent Technologies) was used to identify organic compounds in vessel samples.

Samples collected from fragments of ceramic vessels were pre ground and then ground to powder in a mortar. The weighted ground material (5 g) was extracted in a Soxhlet apparatus for 4 h. The extraction mixture contained two solvents: methylene chloride and methanol (200 mL, 2:1 v/v) and 100 μL of standard solution (tetracosane, 1 mg/mL). The extracted lipid fraction was evaporated to dryness and then dissolved in 2 mL of hexane. Portions of 0.5 mL extract were transferred to chromatography vials and evaporated from atmospheric pressure in a stream of nitrogen to dryness. The obtained dry residue was subjected to derivatisation (silylation). 100 μL of a derivatising mixture composed of two reagents was used to convert the analytes into their volatile derivatives (TMS esters), and the reagents used were N,O-bis(trimethylsilyl)trifluoroacetamide and trimethylchlorosilane (100:1 v/v). The sample with the mixture was heated for 30 min at 75 °C. Following this process, 300 μL of hexane was added to the sample and GC-MS analysis was performed.

The analytes were separated on an HP-5MS (5%-diphenyl-95%-dimethylpolysiloxane) column at a carrier gas (He) flow rate of 0.9 mL/min. The injected sample volume was 1 μL. The injector was operated in a mode without separating the carrier gas flow. The gas chromatograph oven was programmed as follows: the initial temperature was 60 °C, with a temperature increase of 12 °C/min until a final temperature of 300 °C was reached. The parameters of the mass spectrometer were as follows: the temperatures of the ion source and mass analyser were 230 °C and 150 °C, respectively. Mass spectra were acquired in electron ionisation (EI) mode at a potential of 70 eV and a sweep range of 50–550 m/z.

Qualitative analysis of organic acids and biomarkers was performed using Wiley and NIST08 mass spectral libraries and commercially available standards. Quantitative analysis of fatty acids was performed using the internal normalisation method.

Numerical analysis of fatty acid and biomarker data

A set of fatty acids and fatty acid proportions from components indicated by the Student’s t test method was selected to differentiate between the chemical composition of vase samples from the settlement and the cemetery areas. Furthermore, in this study, these selected components were named feature subset 1. The second, alternative feature subset (subset 2) of acid-related features was selected according to the criterion of variable importance in projection (VIP) determined by the supervised partial least squares—discriminant analysis (PLS-DA) modelling method. A VIP score greater than 1 is a typical rule for selecting relevant variables 11 and might be considered a significant contribution to the explained variable. Scaling and normalisation procedures were used for data pretreatment.

Unsupervised data classification in two clusters has been applied in the feature space of the selected VIP components. The fuzzy C -means (FCM) method 12 , 13 was used to perform classification, allowing the assessment of the probability of an archaeological sample belonging to both groups (cemetery and settlement).

For clustering quality evaluation, the fuzzy silhouette index (SI), Dunn’s partition coefficient (DC) and partition entropy index (PEI) were used. The SI 14 , 15 is calculated using the mean intra-cluster distance ( \({a}_{j}\) ) and the mean nearest-cluster distance ( \({b}_{j}\) ) for each data sample as shown in Eq. ( 1 ).

where the distances are expressed by logical operations on the sample membership degrees. An SI value equal to 1 indicates perfect cluster separation; values near 0 indicate overlapping clusters.

Similarly, the Dunn coefficient 12 is the ratio of the smallest distance between any two clusters to the largest intra-cluster distance found within any cluster, as in Eq. ( 2 ).

where m is the number of clusters, \({C}_{i} ,{C}_{j}\) are two compared clusters, d – the Euclidean distance between the clusters or two data samples x , y in one cluster. When the Dunn index is always above zero, greater values indicate better clustering.

The partition entropy index (PEI) 16 , 17 shown in Eq. ( 3 ) measures the overlap among clusters.

where \(U={[{u}_{ij}]}_{m\times n}\) represents the fuzzy partition matrix of the C -means method with \({u}_{ij}\) as the membership degree of a data sample \({x}_{j}\) , and \(m\) —the number of clusters, logarithm base \(a>1\) . The range of values for PEI is \([0, 1]\) . The closer the PEI value is to 0, the harder and therefore less fuzzy the clustering is.

To verify the consistency of fuzzy C-means clustering prediction with actual division of the examined vessels, the overall accuracy parameter ACC was applied (Eq.  4 )

where \({M}_{m\times m}\) is the confusion matrix 18 in the case of \(m\) classes (clusters).

Statistical analyses were performed using the R language directly in the R Studio environment and the MetaboAnalyst software ( https://www.metaboanalyst.ca ). The Partial Least Squares (PLS) regression was performed using the plsr function provided by the pls library in R . The classification and cross-validation were performed using the corresponding wrapper function offered by the caret package. The FCM algorithm was implemented using the ppclust R library, and the clustering quality indices were computed using appropriate functions from the fclust library.

A permutation test based on prediction accuracy was performed to assess the significance of class discrimination in PLS-DA 19 . In each permutation (100 in total), a PLS-DA model was built between the data (X) and the permuted class labels (Y) using the optimal number of components determined by cross-validation (CV) for the model based on the original class assignment.

Based on binary data on the presence of biomarkers, samples were subjected to clustering analysis using the Ward method and Euclidean distance as a measure of dissimilarity.

The paper focuses on fatty acids and biomarkers that can directly indicate the source of the examined organic residues. The identified fatty acid contents in samples from the Domasław cemetery and the Milejowice settlement are included in Table 2 .

Eighteen acids, primarily saturated, were determined in the samples. C16:1 and C18:1 represented the group of unsaturated acids. C18:2 was determined in sample 113 from Domasław. C6:0, C8:0, C9:0, C10:0, C12:0, C16:0, C18:1 and C18:0 acids were present in all samples. Long-chain acids—C20:0 and/or C22:0—were detected in most samples from Milejowice, and in six from Domasław. C11:0 acid was identified in vessels 42 and 43 from votive pits in Milejowice. This acid was also rare at the cemetery, recorded in urns, rhyta , a censer, and offering vessels. Statistical analyses showed that settlement and burial vessels differentiate most acids C13:0, C15:0, C22:0 and the C22:0/(C16:0 + C20:0) ratio.

Any conclusions about the sources of the examined organic residues based solely on the presence and content of individual acids would be unreliable. Most acids are present in both plant and animal resources. Moreover, the residue composition can change over time, which should always be considered in archaeological samples. Consequently, researchers are looking for another way to interpret the results of chromatographic analyses. One of the methods is based on studying the proportions of selected fatty acids, as it appears that acid proportions can remain unchanged over time. The conclusions presented in this paper were based on the work of Eerkens 20 . Based on his proposed proportions, the most likely sources of the studied residues were designated. The calculated proportions of selected acids are shown in Table 3 .

The acid proportions suggest that most examined samples have a mixed origin. The residue probably came mainly from seeds, nuts, and berries in combination with fat from land mammals (samples 39, 42, 47, 55, 58, 61, 79, 86 from Milejowice and 3, 4, 12, 91, 95, 104, 105 from Domasław). The proportions in grave samples 90, 93, 94 suggest seeds, nuts and land mammal fat. Vessels 40, 43, 46, 49, 53, 72 from the settlement and 10, 101, 106, 108, 111, 113 from the cemetery were of plant origin (nuts and seeds, berries), 70 from Milejowice – originated from seeds and nuts. The C16:0:C18:0 ratio has long been used to distinguish different plant oil sources, with a high (> 3) ratio considered characteristic of poppy seed oil 21 . At vase 105, the ratio was 6.98. A higher C18:1 ratio was detected in rhyta , vases and pots from the cemetery, including most vessels from grave No. 7429 with vases 101 and 104. Scholars suggest that dicarboxylic acid compounds are more likely to be found in plant oils 22 . The presence of dicarboxylic acids and oleic acid (C18:1) increases the possibility that the samples contained acid-rich plant oil or derivative mixtures.

Gas chromatography combined with mass spectrometry made it possible to determine organic compounds from different groups. Based on a literature review, it was possible to select compounds that can be considered archaeological biomarkers. Biomarkers are associated with one specific material or substance, regardless of its origin—plant, animal or mixed. The detected fat is not necessarily an oil but may have been an ingredient of herbs, vegetables or grains.

Methyl dehydroabietate, a dehydroabietic acid derivative, was detected in almost all samples from Milejowice (except 42, 43, 55) and seven from Domasław (3, 4, 12, 90, 91, 93, 94). This acid is classified as a resinous acid and is considered an indicator of resin or its products 23 , 24 , 25 . Resins have hydrophobic properties and can be used to seal unglazed vessels 26 , but they have also been intentionally added to alcoholic beverages to preserve, enhance, and change their flavour 27 , 28 , 29 , 30 . Adding resin to wine to protect it against disease, for medicinal purposes and to cover up off-tastes and off-aromas was a popular and widespread practice throughout the ancient world 31 . Cedrol—sesquiterpene alcohol, found in the essential oil of coniferous trees, was present in settlement vase 55.

Glycerol, a product of lipid degradation, was also observed in most samples from Milejowice (except 55, 79, 86) and in more than half of the samples from Domasław (3, 90, 91, 93–95, 101, 104, 106). Vanillin, a phenolic compound, and vanillic acid (found in elderberry juice, blueberries, strawberries, and alcoholic beverages 32 ) were detected in nine vessels from Milejowice (39, 40, 46, 53, 55, 58, 61, 70, 72) and in all samples from Domasław except 101, 106, 108, 111, 113. Vanillin may originate from tree resin or pine wood/dust, which is documented in the same samples by the presence of methyl dehydroabietate. Acetowanillone, identified in settlement vase 70, a structural analogue of vanillin, is found mainly in wines aged in oak barrels.

Lactic acid, determined in nine vessels from the settlement (39, 40, 42, 46, 47, 49, 58, 61, 70) and eight from the cemetery (4, 10, 90, 91, 93, 94, 95, 104), is one of the essential products of bacterial fermentation, which occurs, e.g., during vegetable pickling or milk fermentation. However, malic acid (a beer and wine ingredient) can also be converted by bacteria into lactic acid, which gives the beer a sour taste 33 , 34 .

Azelaic acid was identified in nine vessels from the settlement (39, 40, 42, 49, 53, 55, 58, 61, 86) and seven from the cemetery (4, 10, 12, 93, 94, 101, 105); oxalic acid in four from Milejowice (40, 46, 55, 58) and three from Domasław (12, 91, 95); suberic acid in five from the settlement (42, 53, 55, 58, 61) and two from the cemetery (4 and 12). Their presence may suggest that the studied residues originated from grain products, including wheat, rye, or barley 35 , 36 .

Suberic acid is produced also during the oxidation of castor oil and is used to produce resins. Acetic acid, observed in vase 4, may indicate the contact with fermented food 34 . It is formed from ethanol under the action of aerobic acetic bacteria (vinegar production), as well as from acetaldehyde, which, as a component of beer, gives it its characteristic flavour and aroma 33 , 34 , 35 . Fumaric acid, confirmed during beer fermentation and wort production 34 , was present exclusively in vase 94 from Domasław. Only settlement vessel 53 produced traces of caprolactone, a fragrance component found in flowers, some fruits and vegetables. Δ-Caprolactone is found in heated milk fat 37 .

Stigmastanol, present in four samples from Domasław (4, 12, 93, 95) and seven from Milejowice (40, 43, 55, 58, 70, 79, 86), also indicated their plant origin. This sterol occurs in vegetable fats or oils of many plants: beans, rapeseeds and herbs. Another noteworthy example is benzoic acid, determined in half of the samples from the necropolis (90, 91, 93, 94, 101, 104, 106, 113) and only one from the settlement (53). Its presence may also indicate that the examined residues originated from plants, as it is a component of plant tissues, especially fruits and vegetables 38 . This acid is detected, for example, in cherry bark, raspberries, and honey. Benzoic acid may also be a degradation product of anthocyanins by ketones in wine 39 .

Of particular importance may be the tiglic and croton acids present exclusively in vase 12 from the Domasław cemetery and 13 containers from this site, such as rhyta , a kernos, censers, a disc-plate, an urn, and offering vessels. Tiglic acid is a compound with a spicy smell, it occurs, among other things, in croton oil obtained from the seeds of laxative croton, a plant from the Euphorbiaceae family, used for medicinal purposes.

Borneol, which appeared in two vases from the cemetery (10, 90) and four from the settlement (39, 42, 55, 79), is a compound from the terpene group with a camphor-like fragrance. It is a component of many essential oils, pine resin, and herbs, e.g., tansy, savoury, sage, and plants from the wormwood family. Like croton oil, it has medicinal and toxic effects and may cause eye and skin irritation and vomiting. Borneol was found mainly in the most distinctive vessels from the cemetery, such as an urn, a rhyton and offering vessels, At the Milejowice settlement, it occurred in dippers, a plate-disc and bowls. Phenoxyethanol was detected only in funerary vases 90, 91, 93, 94 and 95, two miniature rhyta and an urn. It can be found naturally in some plants, such as onions and chicory, and helps control and prevent the growth of bacteria, yeasts and moulds. Inulin, an extract from chicory root, has been used as a sweetener. Some beer brewers use roasted chicory to add flavor to stouts, or to augment the hops. Roots contain essential oils similar to those found in plants in the related genus Tanacetum . Carvacrol was detected only in three vases from Milejowice (55, 58, 61). There are many sources of carvacrol, including various kinds of thyme and marjoram.

Adipic acid from three funerary samples (90, 91, 101) occurs naturally in beets and sugarcane. Gramine (donaxin), found in funerary vase 101, is a naturally occurring indole alkaloid found in several plant species, such as silver maple and Hordeum , a genus of grass that includes barley 40 . 9,12-Dihydroxyoctadecanoic acid (Z,Z), present in a funerary vase with a funnel-shaped rim and conical neck (101) and in all vases with cone-shaped necks (105, 106, 108), is a linoleic acid derivative and a component of most vegetable oils and animal fats, found in many foods, e.g., legumes, cloves and nuts. It is produced through the hydration of ricinoleic acid, which is found in large amounts in castor oil and has historically been reported to be a significant resource with various uses in ancient times.

3,4-dihydroxybutyric acid found in vase 72 from Milejowice, is believed to be formed via the degradation (cooking) of di- and polysaccharides, including lactose. Farnesol, an alcohol from the terpene group obtained from linden flower oils, is used mainly as the lily-of-the-valley fragrance and is a component of many essential oils, including lily of the valley, linden and acacia. It was found in painted vases 47 and 49 from the settlement.

The contents of funerary vessel 113 proved very distinctive, suggesting the presence of plants and honey. The detected spirost-8-en-11-one, 3-hydroxy- is a component of sugar plants. The sample also contained 7,8-epoxylanostan-11-ol, 3-acetoxy, which is a cholesterol-based alcohol with anti-inflammatory and antibacterial properties that occurs in many plants. Furthermore, a propolis ingredient, 17-pentatriacontene, 1-heptatriacotanol, was identified. Additionally, 1-heptatriacotanol, an alcohol with antioxidant, anticancer, and anti-inflammatory properties, was confirmed. It occurs in various waxes, e.g., beeswax or plant waxes (jojoba oil). Last, the studies detected 1-monolinoleoylglycerol—an ether, glyceride consisting of one chain of fatty acid (linoleic acid) and glycerol. It occurs, among others, in plants of the Lamiaceae family, which are used as spices, medicines and teas.

Valproic or valeric acid was present in vases 90 and 91 from the cemetery and vessels 42 and 43 from settlement votive pits. Valproic acid is a saturated monocarboxylic acid and a valeric acid derivative. It occurs naturally in some foods, such as berries. It has sedative and anticonvulsant properties.

The presence of dibutyl phthalate, a phthalic acid present in six vessels from Milejowice and nine from Domasław, may indicate the thermal processing of products in vessels 41 or may result from sample contamination.

Acid data analysis and classification

In this study, based on acid-related data, we applied the FCM algorithm to cluster samples of ceramic vases from the settlement in Milejowice and the cemetery in Domasław. Features important for the data analysis were selected by t tests with a threshold of 0.05 and VIP values were obtained with PLS regression (Fig.  2 ).

Important features selected for sample classification: ( a ) features of subset 1 selected by t -tests with a significance threshold of 0.05. Blue circles represent features above the threshold (p); values are transformed by –log10; ( b ) Features of subset 2 selected by the VIP value (score above 1). Characteristics of the biomarker distribution in vase samples, including a grouped histogram of biomarker occurrences in samples from the cemetery and settlement ( c ) and a clustered heatmap of biomarkers for which the minimum absolute difference between the two groups of vases in histogram was at least 2. Additionally, the frequently occurring lactic acid was considered ( d ).

The results were two subsets of variables used independently in the analysis. Subset 1 includes acid-related variables such as C13:0, C15:0, C22:0 and C22:0/(C16:0 + C20:0) (Fig.  2 a,b). The set of variables with the highest VIP value (> 1) included the same components, except for the additional C12:0/C14:0 acid proportion. The test values are listed in Table 4 .

Using the fuzzy C -means method, the dataset was grouped into two clusters, where each data point belonged to each cluster to some extent. Clustering results are shown in Fig.  3 a and Fig.  3 b. The obtained results show that the clusters largely correspond to the sample origin. The probability plot for feature subset 1 (Fig.  3 c) shows that cluster 1 contains samples from the necropolis and five samples from the settlement, while cluster 2 contains only samples from the settlement. Adding acid proportion C12:0/C14:0, another considered feature slightly reduced the probability that the samples belonged to the selected clusters (Fig.  3 d) but did not significantly disturb their previous distribution. With the data in Fig. 3 c,d, adopting more flexible grouping rules, e.g., more restrictive than a classification cut-off at a probability of 0.5 was possible. The requirement of a higher probability of class membership leaves some samples out as unclassified due to uncertainty.

Illustration of the clusters of archaeological samples from the cemetery and the settlement in the plane of the PCA main components for the selected feature subset 1 ( a ) and subset 2 ( b ). Each ellipse is a 95% confidence ellipse for a 2D normally distributed data set. The probability of samples belonging to clusters 1 or 2 based on the selected acid data is also presented for feature subset 1 ( c ) and subset 2 ( d ). Confusion matrices for feature subset 1 ( e ) and subset 2 ( f ).

Figure  3 e,f represent the confusion matrices obtained for the two feature subsets. They confirm the obtained probability results and quantify the quality of the archaeological sample classification. The ratio of the sum of diagonal elements to the sum of all matrix elements represents the classification accuracy obtained from clustering. For both matrices, it is 0.84 and 0.81, respectively. It means that features selected by the Student’s t -test provide a better separation of clusters than features selected by the PLS-DA method and, simultaneously, ensure better compliance with their actual division.

Table 5 includes three different indicators of fuzzy clustering effectiveness explained in Eqs. ( 1 )–( 3 ).

Dunn’s partition coefficient (DC) reaches 0.79, which suggests that the clustering is not very fuzzy, and the crisp sample grouping methods can also be applied. Partition entropy index PEI = 0.35 in the range [0,1] informs that the uncertainty within the proposed partition is relatively low, which confirms the observations about the DC. The Fuzzy Silhouette Index value of 0.76 leads to the same conclusions.

Biomarker data clustering

The vessels yielded different biomarkers, most notably benzoic acid, vanillin, and phenoxyethanol. The analysis of histogram and clustering results revealed that some biomarkers were more common in settlement samples (Fig.  2 c,d). These included methyl dehydroabietate, glycerol, azelaic, suberic, adipic acids, and stigmastanol. Vanillin, and benzoic acid were most frequent in cemetery samples. Grave vases had a higher plant oil content.

Vases were most differentiated by the benzoic acid, which were detected in 62.5% of funerary vessels and only 6.5% of settlement vessels. Lactic acid was present in equal proportions in settlement vases and funerary vases with funnel-shaped rims. However, there was no lactic acid or dibutyl phthalate in grave vases with distinguished conical necks. In contrast, 9,12-octadecadienoic acid occurred in all vases with conical necks, one vessel with a funnel-shaped rim, and in none of the settlement containers.

The cluster analysis of the identified biomarkers showed that vessels from the settlement were more similar to one another than were vases from the cemetery. Sample 113 differs from the others and is closer to the pattern recorded in settlement vases.

The organic residue analysis demonstrated that most of the vases from the cemetery and settlement were of a mixed nature, originating from seeds and nuts and berries, and approximately 40% had a plant character. The vases might have come into contact with food based on cereals, herbs, honey, fruit, animal fat (meat or milk), oily plant products and fruits, bee products, and resins. Due to their design, vase-shaped vessels were preferred for storing drinks. Cereal cultivation was confirmed by botanical analyses of samples from Domasław, which showed the presence of burnt wheat and millet grains in vessels and graves (studies by A. Sady-Bugajska). We can assume that vessels contained particularly fermented beverages, most likely ale gruit of wheat, barley and/or rye, as indicated by markers of these cereal species. Chemical evidence of millet (miliacin) combined with possible fermentation markers (bacteriohopanoids) in drinking vessels from Mont Lassois seems to confirm the production of millet beers 42 .

Plant ingredients, e.g., stigmastanol, cedrol, herbal ingredients, such as carvacrol and borneol, and bactericidal or medicinal ingredients (valproic acid) could be added to beverages as flavourings, to extend their storage time (preservatives), but also to enhance their effect. The addition of herb, resin and honey imparted different drink properties and increased variety. Phenolic compounds, like vanillin, may come from malt (sprouted and dried cereal grains) and affect the flavour and clarity of beverages. Simple phenols may also be derivatives of benzoic acid present in the samples 43 . The presence of tiglic and croton acid may indicate that the vessels contained oils added for medicinal purposes, flavouring and symbolic reasons, which is suggested by their presence only in vessels associated with offerings.

We may suspect mead in vessel 113. Relatively few bee products were found in the vases, which is surprising considering the very sour or tart taste of the ancient beer (unless we consider the presence of benzoic acid in the funerary vessels as a possible propolis residue). Honey and beeswax frequently occur in archaeological ceramic containers—the former as a sweetener and the latter as a vessel sealant. Honey is documented mainly by pollen analyses, among others, in bronze craters from princely graves in Heuneburg-Hohmichele, Heuneburg-Speckau, Hochdorf, Glauberg and Niedererlbach 44 , 45 , 46 , 47 , 48 , 49 , or recognised as a honeycomb in Lavau 50 , 51 .

Some fruit components (benzoic, valproic, levulinic acids, vanillin) may come from fruit wine and sugars from tree saps, e.g., birch and maple, which were undoubtedly consumed both fresh and fermented. It is possible that alcoholic barley milk beverages, made by mixing malt extract with milk were also consumed. Alcohol made from sap or fruits was archaeologically attested 42 . There is also evidence for combining beers, wines, and meads to make mixed beverages called grogs. Nordic peoples preferred a hybrid beverage, in which many ingredients were fermented together, including locally available honey, fruits, cereals, and sometimes imported grape wine 52 . Birch tree resin, juniper, bog myrtle, yarrow, bog cranberry, and lingonberry were also used as additives.

Archaeological evidence shows that feasting was significant in the Hallstatt period and gave political power 53 , 54 , 55 , 56 . Drinking together and providing alcohol forged social prestige and demonstrated power and wealth. Almost all elite graves from this period contained vessels for distributing alcohol. Similar vessels from settlements emphasised the role that alcohol played during feasts, festivals, meetings and celebrations. The most spectacular pieces of libation pottery are segmented vases with funnel-shaped rims and conical necks, which appeared at the onset of the Iron Age due to the influence of Hallstatt. Through these “Hallstatt” patterns, vases also highlighted their owners’ status. The Domasław cemetery and the Milejowice settlement yielded many references to feast and libation rituals. In Milejowice, the massive, decorated vases 42 and 46, containing other vessels, animal bones, and bronzes, undoubtedly had a votive character, probably similar to containers from the well (39, 40). Potentially, they had initially served for storage or fermentation but were later used in ritual activities as food or drink sacrifice accessories. Other vessels are not that distinctive. Despite their inconsistent distribution patterns, scholars indicate that graphite-coated and painted vases with funnel-shaped rims and conical necks were more “prestigious” than daily household vessels 5 . Containers with fermenting liquids must be well-sealed with wax or resins and buried in the ground, like some larger storage vessels discovered in Milejowice, e.g., with identified tar. Smaller ones might, in turn, have been used to distribute (perhaps diluted) alcohol.

The vessel sets discovered in Domasław were undoubtedly used for storing, serving and consuming beverages. It seems that vessels with funnel-shaped rims, most often deposited pairwise, were used by an increasing number of people during funerary ceremonies. Specimens from the early Hallstatt period were smaller, but they became the largest funerary vessels in graves over time. These vessels were surrounded by small cups and bowls, often placed inside them in substantial numbers. Sometimes, plate-shaped bowls were placed as lids on top of the vases. Two of the examined vases contained small bronze vessels which, as shown in the depictions of the late Hallstatt period Situla Art in the Southeast Alps 57 , were used to serve alcohol. Some depictions also show dry products measured in large vases, such as wheat grains, semolina, herbs, raisins or cheese. Vases with cone-shaped necks probably played a different role and were repeatedly placed next to crater-shaped vases, often covered, which may explain differences in the share of, among others, benzoic acid. A comparison of vases from the same graves revealed that they contained different products.

We might assume that decorated vases, both at the settlement and the cemetery, served as beverage containers. Undoubtedly, the products used for daily and funerary activities were diverse, and some might have been associated with taboos. This may explain the differences between the vessels found in these two contexts. The study demonstrated that some compounds were present only in vessels from one context.

The consumed ale was flavoured with a selected mixture of herbs ( gruit ). It is possible that each family/community had its original herbal mixture or recipe passed down from generation to generation, or the composition was subject to various instructions and prohibitions. Different herbal mixtures based on nearby plants were used depending on the occasion for which the beer was prepared. Like hops today, gruit was supposed to preserve the drink and give it the right taste, aroma, and desired properties. The principal bittering agents in the early medieval European beers were bog myrtle, yarrow, meadowsweet, and other herbs 43 . For example, native rosemary, mint, and thyme were added to a fermented emmer wheat and barley beverage at Genó, near Barcelona in Spain 58 . Mugwort was a hypothetic additive (alongside carrot) to a dark, sour barley beer 59 at the settlement of Hochdorf.

Some plants with symbolic, flavouring, intoxicating, medicinal or poisonous properties could only be used in funerary and offerings contexts (e.g. croton oil). Presumably, flour/groats/barley, milk/cheese, wine/beer, and even blood, mentioned in the ancient sources as obligatory for libations and sacrifices were used, which could explain the combination of animal and plant fats in the vessels. Animal fats may also have come from the leather bottles used to transport liquids. The multitude of uses of resins and bee products, such as sealing, polishing, preserving, sweetening, flavouring., does not allow us to assess for what purpose they were used in Domasław and Milejowice. The resins were more common in settlement vessels, which may have been caused by the need to seal containers that are used repeatedly. Some aromas, oils, and spices could be imported, similar to other prestigious products.

Conclusions

Analysis of vases from the Domasław cemetery and Milejowice settlement reveals that they were used to store a variety of beverages, including beer made from wheat, barley, and rye. These vessels contained a diverse range of ingredients, such as fruits, herbs, plant oils, animal fats, honey, and resins. Their content varied in funerary and settlement contexts due to the use of certain plants as well as specific ingredients that imparted the desired properties.

Feasting was crucial during the Hallstatt period, demonstrating social status and power, as evidenced by the presence of drinking sets in elite graves. Richly decorated vases found in the cemetery and in the offering settlement context, suggest their important role in ceremonies. The study highlights the complexity of food and drink preparation, providing insights into the eating habits and rituals of the Hallstatt communities. Consequently, it is a foundation for further exploration of the nature of vessels and the assessment of different consumption practices within the community.

The statistical analysis proved effective in capturing the differences between chemical profiles of vessels deposited in two distinctive contexts, as well as the use of various ingredients in graves, deposits and settlement features. Archaeological data, due to their complexity and often incompleteness, are among the most difficult to analyze and interpret. Hence, this article utilizes statistical analyzes and machine learning methods as a tool of facilitating further interpretation of chemical data. The clustering method used showed the statistical differences in chemical compositions, which may be ambiguous for single samples, given the possibility of multi-faceted use of individual types of prehistoric vessels.

Data availability

The datasets used and/or analyzed during the study are reported in the article.

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The paper is part of a project: Feeding and ritual practices of the Early Iron Age based on the settlement in Milejowice and the necropolis in Domasław. Between the function and meaning of the ceramic “collections” (2021/41/B/HS3/02531), financed by Narodowe Centrum Nauki (National Science Center).

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A.J. and J.K.-C. conceived the experiments, A.R and A.J. conducted the experiments, A.R., A.J., J.S.-N., J.G., and J.K.-C. analysed the results, A.R., A.J., J.S.-N., J.G., and J.K.-C. wrote the original draft, A.R. and A.J. carried out the review and editing. All authors reviewed the manuscript.

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Rosiak, A., Józefowska, A., Sekulska-Nalewajko, J. et al. Funerary vs. domestic vessels from the Hallstatt period. A study on ceramic vases from the Milejowice settlement and the Domasław cemetery. Sci Rep 14 , 19942 (2024). https://doi.org/10.1038/s41598-024-70219-7

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Received : 10 April 2024

Accepted : 13 August 2024

Published : 27 August 2024

DOI : https://doi.org/10.1038/s41598-024-70219-7

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