monkey justice experiment

Find anything you save across the site in your account

How We Learn Fairness

A pair of brown capuchin monkeys are sitting in a cage. From time to time, their caretakers give them tokens, which they can then exchange for food. It’s a truth universally acknowledged that capuchin monkeys prefer grapes to cucumbers. So what happens when unfairness strikes—when, in exchange for identical tokens, one monkey gets a cucumber and the other a grape?

When Sarah Brosnan and Frans de Waal carried out just this experiment, in 2003, focussing on female capuchin monkeys, they found that monkeys hate being disadvantaged. A monkey in isolation is happy to eat either a grape or a slice of cucumber. But a monkey who sees that she’s received a cucumber while her partner has gotten a grape reacts with anger: she might hurl her cucumber from her cage. Some primates, Brosnan and de Waal concluded, “dislike inequity.” They hate getting the short end of the stick. Psychologists have a technical term for this reaction: they call it “disadvantageous-inequity aversion.” This instinctual aversion to getting less than others has been found in chimpanzees and dogs , and it occurs, of course, in people, in whom it seems to develop from a young age. The psychologists Alessandra Geraci and Luca Surian have found , for example, that babies as young as twelve months prefer fair-minded cartoon animals to unfair ones.

And yet, for humans, an aversion to getting less is just one aspect of unfairness. Unlike other animals, we sometimes balk at receiving more than other people. Technically speaking, we experience “advantageous-inequity aversion.” In some situations, we’ll even give up something good because it’s more than someone else is getting. In those moments, we seek to insure that the distribution of goods remains fair. We don’t want the long end of the stick, either.

It seems likely that our aversion to being disadvantaged is innate, because we share it with other animals. The question for psychologists is whether our aversion to benefitting from inequality is innate, too—or, alternatively, if it’s learned through some form of socialization. In December, the psychologists Peter Blake, Katherine McAuliffe, Felix Warneken, and their colleagues published the results of experiments designed to answer this question. Their research spanned seven nations—India, Uganda, Peru, Senegal, Mexico, Canada, and the United States—and looked at close to nine hundred children, aged four to fifteen. They examined whether advantageous-inequity aversion—A.I., as they call it—emerges in all cultures, and, if it does, whether it emerges in the same way everywhere.

Their method was relatively simple. They sat two children down at a table, each in front of an empty bowl. Above each bowl was a tray, onto which the experimenter placed candy. Often, she distributed candy unfairly: she might place four candies on one tray and only one on the other. The child being tested then faced a choice. She could pull a green handle to accept the presented candies, causing them to fall into their respective bowls—or she could pull a red handle to reject them, causing all the candies to fall into a third, off-limits bowl, in the center.

The researchers found that, all over the world, children tended to reject the candies when the split favored the other child. (That is, they rejected disadvantageous inequity, or D.I.) They also found that some, older kids would reject advantageous offers. None of that is surprising. A.I. has been documented among adults many times in the past; in one early study , from behavioral economist George Loewenstein and his colleagues, as many as sixty-six per cent of participants disliked getting more than someone else. The surprising part is that the kids only displayed A.I. in three countries: Canada, the United States, and Uganda. In the other countries—Mexico, India, Senegal, and Peru—they enjoyed the sweet taste of inequality.

These results raise some fascinating questions. Why were kids from only certain countries bothered by having an unfair advantage? And were they rejecting those unfair offers because they cared about fairness—or for some other, less obvious reason?

It’s helpful to start by stepping back from the more complicated case of A.I. to the simpler case of D.I. There are lots of reasons to object to disadvantageous inequity, and some are more obvious than others. D.I. is bad substantively, of course, because you get less candy. But it’s also bad socially, because it signals a demotion in status. In fact, when kids reject disadvantageous offers, they’re often most concerned about their social status, rather than with the candy itself, or with abstract ideas like equality. It’s not about right or wrong. It’s all about me : how do I come off in this scenario?

The importance of social hierarchy in the rejection of disadvantageous unfairness has been cleverly demonstrated in several experiments. In one study , the psychologists Mark Sheskin, Paul Bloom, and Karen Wynn had kids choose between getting one token and giving one to another child, or getting two tokens and giving three to the other kid. “You might think that the latter is the better choice because both children get more,” Bloom writes, in his book “Just Babies.” Often, though, the children chose the first option—just one token each—insuring that they wouldn’t get less than someone else.

In another version of the study, Bloom and his colleagues offered a choice between two tokens all around, or one for the subject and none for her counterpart. Five- and six-year-olds preferred the second option: that is, they gave up a reward in exchange for having more than their peers. “We have a natural aversion to getting less—not to inequity,” Bloom told me. The kids’ behavior isn’t principled; on the contrary, Bloom believes, it seems motivated by something very much like spite. And the message is clear: I want to emerge on top. The absolute number of candies matters less than my relative status.

If D.I. is really about status rather than fairness, could A.I. be about status, too? Rejecting an advantageous offer, after all, also sends a social signal. If you live in a society where ideas of fairness and equality hold a privileged position, then it becomes meaningful to show yourself as embracing those ideals, even at personal cost. Those around you might feel that, since you’re the type of person who believes in equity no matter what, you’re valuable to society, and worthy of respect. From this perspective, both D.I. and A.I. achieve the same end: making sure you maintain status. Perhaps, for older kids who are transitioning into adolescence, status doesn’t always come from having more. It could also flow from being an admirable role model.

If status really is the driving force behind both D.I. and A.I., it would explain one of the study’s relative outliers: Mexico. When the experiment was run there, very few of the children exhibited A.I.; moreover, D.I. appeared to develop far later than in other societies. The Mexican children, in other words, tended to accept all offers, however unequal in any direction. The authors point out that, in that particular sample, most of the kids already knew each other. Perhaps they had already developed reputations, and, as a result, what happened in the experiment had no real implications for their social hierarchy. They were free to enjoy the candy all by itself, without social signals on the side.

Still, even if A.I. and D.I. have a lot in common—even if they’re both about status—the research from Blake and his colleagues suggests that they are different in at least one fundamental way. D.I. is innate: all over the world, and in the animal kingdom, getting less than others is perceived as an insult. A.I., on the other hand, seems to be a product of social life or culture. Globally, at least among children, it appears to be very unevenly distributed. In Canada, the United States, and Uganda, the study shows that older kids are more likely, on average, to reject an advantageous offer than an equal offer. By contrast, in Mexico, Peru, India, and Senegal, they willingly accept getting more. In the past, studies of A.I. have focussed on so-called WEIRD societies—Western, educated, industrialized, rich, and democratic. As a result, the uneven distribution of A.I. went beneath the radar.

To explain its uneven distribution, Blake and his colleagues point to a number of potential causes. The most prominent is “Western norms.” They suggest that advantageous-equity aversion is more prevalent in Western societies because, in the West, equality and the abstract notion of “fairness” are valued as goods in their own right; it’s only within that framework that sacrificing your self-interest in the name of fairness comes to be linked with status. (In recent years, of course, Western societies have been wrestling with the problem of rising inequality—an irony on which the researchers choose not to dwell.) In an earlier study , McAuliffe, Blake, Warneken, and their colleagues found that, while subjects exhibited D.I. even in the absence of a visible partner, A.I. only emerged in social situations. This suggests that A.I. might require certain kinds of social environments to thrive.

If it’s Western culture that encourages A.I., then why is it so common in Uganda? Blake and his colleagues posit that the answer lies in the specific subset of the Ugandan population they surveyed. They recruited children from schools that had Western teachers, and in which students were frequently exposed to Western researchers. Perhaps, they write, that environment had changed the students’ sense of fairness. This reasoning seems a bit thin: aren’t other societies also exposed to Western norms, especially in the modern age of ubiquitous smartphones and mass media? “It remains possible that children in Uganda reject an advantage for other reasons not linked to Western norms,” the authors write. “If this is the case, we would expect to see A.I. emerge in children in other communities in Uganda with similar cultural norms but different institutional structures.”

Behind the question of how “Western” A.I. is, a broader question looms. What factors in society could create a norm whereby it’s valuable to establish yourself publicly as someone who doesn’t want to receive more than others? In the same set of studies in which he found that, under some circumstances, up to sixty-six per cent of adults experienced A.I., George Loewenstein tried to tease out what conditions might give rise to advantageous-inequality aversion in the first place. He started by asking subjects to imagine themselves in a specific business scenario. In the first scenario, they had invented a new type of ski with someone; in another, they were splitting tax revenue from a vacant lot with a neighbor; and, in a third, they were in conflict with a sales manager at a retail outlet. In each of these scenarios, their preëxisting relationship with their counterpart was described as positive, negative, or neutral, and the financial payments were either equal or representative of disadvantageous or advantageous inequity. As expected, when it came to D.I., pretty much no one enjoyed receiving less than the co-inventor, business partner, or manager. A.I., by contrast, was unevenly distributed; in some situations, it was absent altogether. It emerged readily in the invention and vacant-lot scenarios— if the preëxisting relationship was positive or neutral; it was relatively infrequent in the retail scenario; and, if the relationship was negative, it disappeared across the board. (In that case, people preferred to come out ahead of their counterparts.)

Based on his participants’ choices, Loewenstein divided them into three groups: saints, loyalists, and ruthless competitors. Saints preferred equality over everything else; they were concerned with fairness for its own sake. Loyalists preferred equality in positive relationships, but, in negative ones, they sought A.I.—they approached the relationship socially, seeking to create loyalty by giving up their unfair advantages. Ruthless competitors always preferred getting more. The relative percentages of the saints, loyalists, and ruthless competitors were twenty-four, twenty-seven, and thirty-six, respectively. (Eighteen per cent couldn’t be classified.) Then, in a follow-up, Loewenstein clarified the preëxisting relationships, providing his subjects with several paragraphs of explanation as to why those relationships were positive, negative, or neutral. Under that condition, the number of saints and ruthless competitors fell, while the proportion of loyalists rose to over half—fifty-two per cent.

When participants received more context for the study’s social scenarios and became more invested in their relationships, in other words, they gave up more to nourish and maintain them. And they are wise to do so. The results of another set of experiments show that the more someone earns in a context of inequality, the more hostile reactions from others she provokes. People dislike those at the top of the heap more when the heap itself is taller.

All of these findings have something to say about why we value fairness. Our ideas about fairness are relativistic, rather than absolute. In many ways, we approach fairness as a form of social signalling. People tend not to care about equality as an abstract principle; instead, they use fairness to negotiate their place in a social hierarchy. And, for that reason, we’re especially willing to give up our unfair advantages when there’s the possibility of strengthening a future relationship.

Could these general principles explain why A.I. appears earlier or more often in some societies? Possibly, but there’s a lot more research to do before anything like a clear-cut answer emerges. One thing we do know is that culture plays a role—but what kind of culture? Can it be taught? Maybe, if we can figure out the answer to that question, we’ll be able to build a world where there are more saints and loyalists—and fewer ruthless competitors.

• Skip to main content
• Keyboard shortcuts for audio player

13.7 Cosmos & Culture

Feeling down watching this will help.

Barbara J. King

Two white-headed capuchin monkeys (also known as the white-faced capuchin or white-throated capuchin) on Gorgona island, off Colombia's Pacific coast. AFP/Getty Images hide caption

Two white-headed capuchin monkeys (also known as the white-faced capuchin or white-throated capuchin) on Gorgona island, off Colombia's Pacific coast.

Every now and then, just once in a while, really, someone asks me to do something unexpected and a little bit onerous, something I feel I shouldn't have to do, and I catch myself muttering: "But that's unfair!"

Then, in the next moment, I do two things.

I vow never to say it again. It's too much like a whine and I'm not a whiner. Anyway, why should I, a grown-up, after all, expect fairness to be a part of my every hour and every day?

Next, I re-watch a favorite video clip, one that stars two capuchin monkeys. It never fails to recalibrate my mood, changing it for the better. Here, see for yourself:

As the well-known primatologist Frans de Waal can be heard explaining in that clip — or with a bit more detail in the one that follows this paragraph — capuchin monkeys "get" unfairness. In the filmed experiment, one of the monkeys is originally quite satisfied with a cucumber reward for carrying out a task. But the animal quickly becomes piqued when a second monkey is given a vastly preferable grape reward for carrying out the exact same task.

The piqued monkey, in a nonhuman-primate sort of way that looks pretty sophisticated, grasps the situation's unfairness. And it's not just this capuchin monkey, but others as well, as explained by Sarah Brosnan and de Waal in their article from 2003 called " Monkeys reject unequal pay .").

Watching those two monkeys in the video, I feel it's OK to be a little less hard on myself for any verbal outbursts about unfairness — maybe it's a primate thing to react in a peeved way when our expectations of fairness are violated.

Of course, the human world contains genuinely significant injustices — too many of them. Such inequities are no laughing matter. But I'm not thinking about those here; I mean only the small injustices we all experience on occasion.

And in that context, watching those capuchins makes me laugh, and helps me to get over myself.

Barbara's most recent book on animals will be released in paperback in April. You can keep up with what she is thinking on Twitter: @bjkingape

• Frans de Waal
• Sarah Brosnan
• capuchin monkeys

Monkeys for equal pay (and every cat for itself)

In a campus appearance hosted by UC Berkeley’s Greater Good Science Center, primatologist Frans de Waal discussed his research on "the emotional side of animal behavior" — behavior, he insists, more like our own than some humans admit.

By Barry Bergman

March 11, 2015

A philosopher once wrote to Frans de Waal, explaining the flaw in the primatologist’s findings on what he calls “the emotional side of animal behavior.”

It was impossible that monkeys have a sense of fairness, the philosopher said, “because the sense of fairness was discovered during the French Revolution.”

Frans de Waal: Like humans, along with aggression, chimps’ behavior includes reconciliation, empathy and consolation. (UC Berkeley photos by Barry Bergman)

On Monday, in a lively campus appearance hosted by UC Berkeley’s Greater Good Science Center, de Waal offered compelling evidence that capuchin monkeys — namesakes, though presumably not co-religionists, of an order of Catholic friars — not only recognize inequity, but are quick to challenge it.

Before a packed house at Sibley Auditorium, de Waal played a video of an experiment he’d done with pairs of capuchin monkeys, housed side by side in glass cages. In return for handing a pebble to a researcher, one monkey receives a bland piece of cucumber, which she’s happy to get — until she sees that her partner’s reward for the very same task is a tasty grape.

She gives it another try, but instead of a grape gets cucumber again. This time she hurls the cuke back at the researcher, rattles her cage, pounds the floor in angry protest. It’s a tantrum similar, in fact — as another video showed — to that of a human toddler who sees her older brother get a cookie, only to get half herself.

During de Waal’s experiments, he said, monkeys rewarded equitably rejected the cucumber just 5 percent of the time. If their partners received a grape, however, they refused their lower pay at a rate of 50 percent. And when partners were given a grape “for free,” without even having to pick up a pebble, rejections soared.

Such behavior, said the Dutch-born de Waal, now at Emory University, is further evidence that humans are not the only species to boast a moral code, and that morality is separate from God and religion. Instead, it’s related to what he calls the “prosocial tendencies” of primates and other animals, a self-awareness — and awareness of others — that gives rise to emotional responses like reconciliation, empathy and consolation.

“I’ve seen chimps kill each other,” said de Waal, “so I’m very fully aware of their competitive side.” After studying aggression in chimps as a student in the Netherlands, though, “It struck me that after fights they would come together, they kissed and embraced each other, and that was actually more interesting than the aggression itself.”

De Waal on the notion that humans are special: “I don’t believe a word of it.”

And chimps aren’t the only nonhuman animals with a bent for reconciliation. “There’s only one mammal that has been tested where it has not been found, and that’s a mammal many of you have at home,” de Waal said. “It’s a domestic cat.

“I’m a big cat lover,” he added, “and I’m still waiting for the magical moment.”

The feline, he explained, is a “solitary hunter,” and so has less need to work in tandem with partners, as primates and elephants have proved able to do in his and others’ experiments. But he rejects the distinction many people make between humans and other species, “that what animals do must be instinctive, and what we do is cultural.”

He described the difference between two kinds of macaques, rhesus monkeys and stump-tails, and the cultural influence one can have on the other. Rhesus monkeys, he said, are “very hierarchical,” prone to punishing subordinates and not keen on reconciliation. Stump-tailed monkeys, by contrast, are “very tolerant and engaging.”

“I usually compare them as the New Yorkers and the Californians,” he said.

In one experiment, juvenile stump-tailed and rhesus monkeys were housed together for five months — during which the stump-tails’ mellowness rubbed off on their more belligerent cousins.

“What we’re showing here is how strongly reconciliation behavior in rhesus monkeys can be affected by the social environment,” said de Waal. “Which means that humans, of course, can also be affected by the social environment.”

He cited studies that reveal “big cultural differences” between America and Japan, where children reconcile “much more” than their U.S. counterparts — likely due, according to researchers, to the way teachers in each country handle conflict in class and on the playground.

“Teachers in the U.S., as soon as there’s a fight among kids they step in and stop it,” he said, while in Japan “they let them fight, and reconcile on their own.”

‘The bonobo is an atheist’

During his hourlong talk, followed by questions from the audience, de Waal employed data, humor and videos to break down commonly held beliefs about the differences between human and nonhuman animals. There were chimps showing empathy by unselfishly caring for their partners’ well-being, for example, and a pair of elephants figuring out how to haul in a tricky feeding apparatus by coordinating their efforts.

And while his listeners were rapt throughout, they witnessed plenty of evidence of “yawn contagion,” which, like other manifestations of empathy — human and not — rises and falls in relation to others’ perceived “otherness.”

De Waal, a prolific author whose most recent book is The Bonobo and the Atheist: In Search of Humanism Among the Primates, bristles at the notion that “humans are special,” a conceit, he said, prevalent in the literature of economics and anthropology: “I don’t believe a word of it.”

“The bonobo is an atheist, I think,” he said Monday. “Although maybe the bonobo would be diplomatic and say, ‘I am an agnostic.’

“I’m interested in the evolution of morality,” he explained. “And each time I talk about the evolution of morality people say, well, it comes from God, or it comes from religion. And I’m sort of tired of that. Because I think our current religions are just a couple of thousand years old, and I cannot imagine that 200,000 years ago our ancestors had no rules of right and wrong, or fairness, or whatever. So morality must be much older.”

At the least, he might have added, it predated the French Revolution.

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Published: 18 September 2003

Monkeys reject unequal pay

• Sarah F. Brosnan 1 &
• Frans B. M. de Waal 1  

Nature volume  425 ,  pages 297–299 ( 2003 ) Cite this article

27k Accesses

747 Citations

651 Altmetric

Metrics details

During the evolution of cooperation it may have become critical for individuals to compare their own efforts and pay-offs with those of others. Negative reactions may occur when expectations are violated. One theory proposes that aversion to inequity can explain human cooperation within the bounds of the rational choice model 1 , and may in fact be more inclusive than previous explanations 2 , 3 , 4 , 5 , 6 , 7 , 8 . Although there exists substantial cultural variation in its particulars, this ‘sense of fairness’ is probably a human universal 9 , 10 that has been shown to prevail in a wide variety of circumstances 11 , 12 , 13 . However, we are not the only cooperative animals 14 , hence inequity aversion may not be uniquely human. Many highly cooperative nonhuman species seem guided by a set of expectations about the outcome of cooperation and the division of resources 15 , 16 . Here we demonstrate that a nonhuman primate, the brown capuchin monkey ( Cebus apella ), responds negatively to unequal reward distribution in exchanges with a human experimenter. Monkeys refused to participate if they witnessed a conspecific obtain a more attractive reward for equal effort, an effect amplified if the partner received such a reward without any effort at all. These reactions support an early evolutionary origin of inequity aversion.

This is a preview of subscription content, access via your institution

Access options

Subscribe to this journal

Receive 51 print issues and online access

185,98 € per year

only 3,65 € per issue

Buy this article

• Purchase on SpringerLink
• Instant access to full article PDF

Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others

Parrots do not show inequity aversion

Arbitration supports reciprocity when there are frequent perception errors

Children avoid inefficient but fair partners in a cooperative game

Fehr, E. & Schmidt, K. M. A theory of fairness, competition, and cooperation. Quart. J. Econ. 114 , 817–868 (1999)

Article   Google Scholar  

Andreoni, J. Cooperation in public-goods experiments: kindness or confusion? Am. Econ. Rev. 85 , 891–904 (1995)

Google Scholar  

Fehr, E. & Gachter, S. The puzzle of human cooperation: reply. Nature 421 , 912 (2003)

Article   ADS   CAS   Google Scholar  

Fehr, E. & Gachter, S. Altruistic punishment in humans. Nature 415 , 137–140 (2002)

Johnson, D. D. P., Stopka, P. & Knights, S. The puzzle of human cooperation. Nature 421 , 911–912 (2003)

Milinski, M., Semmann, D. & Krambeck, H.-J. Reputation helps solve the ‘tragedy of the commons’. Nature 415 , 424–426 (2002)

Article   ADS   Google Scholar  

Roberts, G. & Sherratt, T. N. Development of cooperative relationships through increasing investment. Nature 394 , 175–179 (1998)

Wenekind, C. & Milinski, M. Cooperation through image scoring in humans. Science 200 , 850–852 (2000)

Henrich, J. et al. In search of Homo economicus: behavioral experiments in 15 small-scale societies. Am. Econ. Rev. 91 , 73–78 (2001)

Henrich, J. Does culture matter in economic behavior? Ultimatum game bargaining among the Machiguenga of the Peruvian Amazon. Am. Econ. Rev. 90 , 973–979 (2000)

Fehr, E. & Rockenbach, B. Detrimental effects of sanctions on human altruism. Nature 422 , 137–140 (2003)

Kahneman, D., Knetsch, J. L. & Thaler, R. Fairness as a constraint on profit seeking: entitlements in the market. Am. Econ. Rev. 76 , 728–741 (1986)

Zizzo, D. J. & Oswald, A. Are people willing to pay to reduce other's incomes? Annales d'Econ. Stat. 63–64 , 39–62 (2001)

Dugatkin, L. A. Cooperation Among Animals: An Evolutionary Perspective (Oxford Univ. Press, New York, 1997)

de Waal, F. B. M. Good Natured: The Origins of Right and Wrong in Humans and Other Animals (Harvard Univ. Press, Cambridge, Massachusetts, 1996)

de Waal, F. B. M. & Davis, J. M. Capuchin cognitive ecology: cooperation based on projected returns. Neuropsychologia 1492 , 1–8 (2002)

di Bitetti, M. S. Evidence for an important social role of allogrooming in a platyrrhine primate. Anim. Behav. 54 , 199–211 (1997)

de Waal, F. B. M. Food transfers through mesh in brown capuchins. J. Comp. Psychol. 111 , 370–378 (1997)

Article   CAS   Google Scholar  

Tinklepaugh, O. L. An experimental study of representative factors in monkeys. J. Comp. Psychol. 8 , 197–236 (1928)

Andreoni, J., Brown, P. M. & Vesterlund, L. What makes an allocation fair? Some experimental evidence. Games Econ. Behav. 40 , 1–24 (2002)

Falk, A., Fehr, E. & Fischbacher, U. On the nature of fair behavior. Econ. Inq. 41 , 20–26 (2003)

Frank, R. H. in Evolution and the Capacity for Commitment (ed. Nesse, R. M.) 57–76 (Russell Sage Foundation, New York, 2001)

Sanfey, A. G., Rilling, J. K., Aronson, J. A., Nystrom, L. E. & Cohen, J. D. The neural basis of economic decision-making in the Ultimatum game. Science 300 , 1755–1758 (2003)

Frank, R. H. Passions Within Reason: The Strategic Role of the Emotions (W. W. Norton, New York, 1988)

Hirschleifer, J. in The Latest on the Best: Essays in Evolution and Optimality (ed. Dupre, J.) 307–326 (MIT Press, Cambridge, Massachusetts, 1987)

Nesse, R. M. in Evolution and the Capacity for Commitment (ed. Nesse, R. M.) 1–44 (Russell Sage Foundation, New York, 2001)

Dugatkin, L. A. in Evolution and the Capacity for Commitment (ed. Nesse, R. M.) 120–137 (Russell Sage Foundation, New York, 2001)

de Waal, F. B. M. & Berger, M. L. Payment for labour in monkeys. Nature 404 , 563 (2000)

Mendres, K. A. & de Waal, F. B. M. Capuchins do cooperate: the advantage of an intuitive task. Anim. Behav. 60 , 523–529 (2000)

Brosnan, S. F. & de Waal, F. B. M. A proximate perspective on reciprocal altruism. Hum. Nat. 13 , 129–152 (2002)

Download references

Acknowledgements

We thank L. Antonucci, K. Bouxsein, J. Davis, C. Freeman and A. Katz for help with data collection and coding, L. Ruttan for comments on the manuscript and R. Earley for statistical advice. Photo by F.d.W.

Author information

Authors and affiliations.

Living Links, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, 30329, USA

Sarah F. Brosnan & Frans B. M. de Waal

You can also search for this author in PubMed   Google Scholar

Ethics declarations

Competing interests.

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and permissions

About this article

Cite this article.

Brosnan, S., de Waal, F. Monkeys reject unequal pay. Nature 425 , 297–299 (2003). https://doi.org/10.1038/nature01963

Download citation

Received : 14 May 2003

Accepted : 23 July 2003

Issue Date : 18 September 2003

DOI : https://doi.org/10.1038/nature01963

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

This article is cited by

Children’s distributive justice behavior probably not matching their understanding: a systematic review.

• Tianyi Cheng

Current Psychology (2024)

Perceived reward attainability may underlie dogs’ responses in inequity paradigms

• Jim McGetrick
• Hugo Peters
• Friederike Range

Scientific Reports (2023)

Change-Management als Sisyphosarbeit

Gruppe. Interaktion. Organisation. Zeitschrift für Angewandte Organisationspsychologie (GIO) (2023)

Humans, the Norm-Breakers

• Kristin Andrews

Biology & Philosophy (2023)

Are you better than me? Social comparisons in carrion crows (Corvus corone)

• I. G. Federspiel

Animal Cognition (2023)

By submitting a comment you agree to abide by our Terms and Community Guidelines . If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Ian Morris Ian Morris

Leave your feedback

• Copy URL https://www.pbs.org/newshour/economy/monkeys-humans-common-innate-sense-economic-justice

What do monkeys and humans have in common? An innate sense of economic justice

Editor’s Note: Our economic values have evolved over time. If you could return to medieval times, it might seem natural to have a hierarchy of kings, lords, knights and serfs. If you were a part of a small nomadic group, you would rely on the person next to you as much as they relied on you. Out of necessity then, equality would be the norm.

Ian Morris, the Willard Professor of classics at Stanford University, examines how human values have evolved in his book, “Foragers, Farmers, and Fossil Fuels.”  Below, Morris explains how our sense of fairness and economic justice have progressed to where they are today.

— Kristen Doerer , Making Sen$e Editor

“Never work with children or animals,” the saying goes, but fortunately Sarah Brosnan didn’t listen. Plenty of researchers had trained primates to earn snacks by performing simple tasks; but what would happen, Brosnan asked, if she paid some subjects better than others?

She soon found out. Her subjects, Capuchin monkeys in the Yerkes National Primate Center, quickly learned that when Brosnan gave them a pebble, they could get a slice of cucumber by returning the stone. To a few monkeys, though, she gave a better reward: a tasty grape. Seeing their undeserving colleagues earning higher wages for the same work, many monkeys sulked and refused to eat. Others flew into rages, hurling their cucumber back at the biologist. It’s just not fair, they seemed to be saying.

The experiment implied that monkeys have an innate sense of economic justice. Encouraged, Brosnan extended her research to chimpanzees and human children. Her work seemed to show that all primates value fairness of some kind.

Values, most biologists and psychologists conclude, are evolved adaptations — genetic predispositions to think in ways that increase an animal’s chances of passing its genes on. Every species, including us, has evolved its own distinctive values, shared by all members.

But here the problems begin. Human values have evolved biologically across millions of years, and everyone in our species believes in fairness, justice, love and loyalty; and yet we disagree wildly over what these words mean. If you were an anthropologist studying the Hadza people in Tanzania, for instance, you would discover that your hosts think it right and proper that women and men should be equally free to pursue sexual partners. If you moved just 100 miles to live with the Nyamwezi people, you would find that your new hosts consider such behavior anything but right and proper. How can there be such variety in human values if they are biologically evolved? Are the anthropologists wrong? Or the primatologists?

MORE FROM MAKING SEN$E

What explains the glory that was greece actually, sound economic policy.

The answer is neither; but we can only solve this paradox by backing away from the details and looking at the whole of history across the last 20,000 years. When we do this, the kaleidoscope of values observed by anthropologists simplifies into just three patterns, driven by a single fundamental force.

We might call the first of these systems foraging values, because it is associated with societies that support themselves by hunting wild animals and gathering wild plants. From the time modern humans evolved (50,000-150,000 years ago) until about 10,000 BC, everyone on earth lived this way, and a few people still do. Foraging captured very little energy from the environment (typically, 5,000-10,000 kilocalories per person per day), so foragers were extremely poor (getting by on the equivalent of about $1.10 a day), lived in small groups (less than a dozen people), and moved around a lot. It was hard to maintain much political, economic or gender inequality in these conditions. In a famous story, when the anthropologist Richard Lee asked a Kalahari hunter about chiefs he was told “we’re all headmen … Each one of us is headman over himself!” In such settings, people who interpreted fairness as meaning that they should treat everyone the same tended to do better than people who did not.

The second moral system, which I call farming values, because it is associated with societies based on domesticated plants and animals, could not be more different. Agriculture, which was invented around 10,000 BC, provided much more energy than foraging (typically, 10,000-30,000 kilocalories per person per day). As a result, farmers were richer (usually living on the equivalent of $1.50-2.20 a day), lived in larger groups (cities up to a million people), and moved around rather little. For farmers, political, economic and gender inequality were not just possible but necessary, because only hierarchy could hold together the complex division of labor that agriculture required. Virtually every farming society had slaves or serfs and made women into second-class citizens — not because farmers were bullies, but because without forced labor, farming could not function. In these settings, people who interpreted fairness as meaning that everyone was different and should be treated differently — kings better than peasants, men better than women — tended to do better than people who did not.

The third moral system is once again wildly different. I call this fossil-fuel values, because it is found in societies that augment the energy of living plants and animals with that from fossilized plants, by burning coal and oil to power machines. Tapping into fossil fuels unleashes staggering amounts of energy (typically, 50,000-200,000 kilocalories per person per day). This kind of economy was invented in Britain just 200 years ago and then spread around the world. Fossil-fuel users are much richer than farmers (global average income is $25 a day), live in huge societies (Tokyo has 35 more million residents) and have extremely complex divisions of labor — so complex, in fact, that they cannot work well under the kind of top-down hierarchy than dominated the farming world. The more that fossil-fuel societies have moved toward letting people make their own decisions, through free markets, democracy, and free speech, the more they have flourished. Today, people who interpret justice and fairness as meaning that we should treat everyone the same tend once again to do better than people who do not.

There is, of course, a lot more to be said, and I say some of it in my new book “Foragers, Farmers, and Fossil Fuels.” But if this argument holds water, two big conclusions seem to follow.

First, human values are evolutionary adaptations, hardwired into us by biology; but what we take those values to mean depends on how we capture energy from the world around us. Fairness, justice, love, and loyalty mean different things to foragers, farmers, and fossil-fuel users.

Second, if energy capture really does drive values, there is no reason to think that the values of anyone reading this column are the final, perfect form of morality. Energy capture seems likely to change faster in the 21st century than ever before, and so will human values.

People are already merging with their technology and through their technology with each other in ways that would have seemed like magic just 100 years ago. Perhaps a solar-powered, networked world of brain-to-brain interfacing and virtual reality will be even more egalitarian than our own fossil-fuel democracies, and inequality of any kind will be unthinkable.

Or then again, perhaps some people will merge with their technology faster than others, turning into technologically enhanced, immortal posthumans who are as far removed from old-fashioned humans like ourselves as we are from Neanderthals. In a world like that, hierarchy might seem even more natural than it did to Tutankhamen.

We are standing at the threshold of the greatest transformation in what it means to be human since humanity itself evolved. Human values have come a long way from the simple sense of fairness that Sarah Brosnan found among the Capuchin monkeys, but we ain’t seen nothing yet.

Ian Morris is Willard Professor at Stanford University and teaches history, archaeology, and classics. His most recent book is "Foragers, Farmers, and Fossil Fuels: How Human Values Evolve."

Support Provided By: Learn more

Educate your inbox

Subscribe to Here’s the Deal, our politics newsletter for analysis you won’t find anywhere else.

Thank you. Please check your inbox to confirm.

Why Monkeys Care About Fairness And What It Means For Us

Stephannie Stokes | WABE

November 12th, 2014

But why do we care so much about fairness in the first place? 

According to an Atlanta primatologist , we might look to another species to find the answer.

Producer Stephannie Stokes talked with Frans de Waal, C. H. Candler Professor of primate behavior at Emory University and director of Living Links at the Yerkes National Primate Research Center , about his research on primates and fairness to bring us this story.

About a decade ago, Dr. de Waal and a Georgia State University professor Sarah Brosnan noticed something in the behavior of their Capuchin monkeys. In their experiments involving tasks and rewards, they saw that the monkeys weren’t just focusing on the reward they received for the work. They were also watching what the other monkeys were getting as rewards. 

“They shouldn’t be doing that,” Dr. de Waal said, “They should only care about how much work they put in and what they get for it.”

So, to figure out what exactly was going on, the two professors set up an experiment to test how the monkeys would respond if they received different rewards for the same task.

The experiment was simple. Researchers would throw a pebble into the monkey’s cage and its job would be to bring it back. As soon as the monkey did that, it would receive a reward.  Dr.  de Waal shared a video of this fairness experiment in a recent TED Talk :

You’ll see that in the beginning both monkeys get cucumbers as a reward. While Dr. de Waal said cucumber isn’t the most appealing reward for monkeys, it’s good enough for them to do the work. 

But then the researcher switches the reward for one of the monkeys. Instead of receiving a cucumber for the task, that monkey will get a grape, which, it turns out, is a much better reward in the eyes of these primates.

As soon as the researcher does this, you see the monkey who is stuck with the cucumber start to act very differently. It becomes agitated and even throws its reward back at the researcher. 

“Which economists have sometimes called an irrational response,” Dr. de Waal said, “in the sense that cucumber is better than no cucumber. Or, let’s say, if you get a $1,000 and I get $2, I may be upset about that but $2 is still better than no dollars and so I should be happy to accept them.”

But Dr. de Waal said, for monkeys, this kind of behavior actually makes sense. They’re cooperative animals and, when you’re constantly working together, you have to be aware of what your peers are receiving and know if they’re getting a better deal.

For that reason, you’ll see these kinds  of reactions in the behavior of other animals who cooperate, like dogs, crows and, yes, humans too.

Indeed Dr. de Waal said the same experiment has been done with very young children and the resulting behavior is very similar to what you see from the Capuchin monkeys in the video above. For Dr. de Waal, it is no coincidence. This is where he thinks we developed our sense of fairness.

But there is another part of our understanding of fairness that you won’t see in monkeys or dogs. For this fuller sense of fairness, you can’t simply be upset when you’re the one getting less. You also have to care when you’re the one receiving more. This  takes a higher level of cognition and, aside from humans, Dr. de  Waal  has only seen this behavior in apes.

“The chimpanzees may refuse a grape if the other one doesn’t also get a grape. So they want to equalize the outcome,” Dr. de Waal said.

Ultimately, he said this behavior helps avoid conflict. And if you think about it, it makes sense. If you and I do the same work for the same amount of time and you end up earning fifty dollars more than me, I’m probably going to feel some resentment towards you. 

But while this theory tells us how we may have developed our sense of fairness millions of years ago, Dr. de Waal thinks it still could be relevant to people today–particularly when you think of fairness in terms of equality.

“In human society, it’s sort of interesting, inequity I think is just as badly regarded as in monkey society,” Dr. de Waal said. “We officially accept inequities, but it’s not good necessarily for the fabric of society if some people skim off all the good stuff and the others get nothing.”

Top Stories

Harris, Walz plan bus tour across South Georgia

• Week In Review

WABE's Week In Review: More state election board changes could disrupt November and Georgians show up at the DNC

Atlanta lost its host bid, but Georgia still left its mark at the Democratic National Convention

• Delta Air Lines

Delta Air Lines COO departs amid flight cancellations and federal investigation of company

Georgia sheriff's deputy dies days after being shot while serving a search warrant

• Early Childhood Education

City Schools of Decatur to build new early learning center on Electric Avenue

• Share full article

Advertisement

Supported by

What Monkeys Can Teach Us About Fairness

By Nicholas Kristof

• June 3, 2017

Monkeys were taught in an experiment to hand over pebbles in exchange for cucumber slices. They were happy with this deal.

Then the researcher randomly offered one monkey — in sight of a second — an even better deal: a grape for a pebble. Monkeys love grapes, so this fellow was thrilled.

The researcher then returned to the second monkey, but presented just a cucumber for the pebble. Now, this offer was insulting. In some cases the monkey would throw the cucumber back at the primatologist in disgust.

In other words, the monkeys cared deeply about fairness. What mattered to them was not just what they received but also what others got.

Monkeys aren’t the only primates instinctively offended by inequality. For example, two scholars examined data from millions of flights to identify what factors resulted in “air rage” incidents. One huge factor: a first-class cabin.

An incident in a coach section was four times as likely if the plane also had a first-class cabin; a first-class section increased the risk of a disturbance as much as a nine-hour delay did.

We are having trouble retrieving the article content.

Please enable JavaScript in your browser settings.

Thank you for your patience while we verify access. If you are in Reader mode please exit and  log into  your Times account, or  subscribe  for all of The Times.

Thank you for your patience while we verify access.

Already a subscriber?  Log in .

Want all of The Times?  Subscribe .

Advertisement

Envious monkeys can spot a fair deal

By Roxanne Khamsi

13 November 2007

Monkeys invest less energy in a task if they see other monkeys receiving better rewards for the same effort, researchers report. They say that their experiment provides new evidence that non-human primates can feel envy. The findings could also help explain why humans have such a keen sense of fairness, according to experts.

Previous studies have found that monkeys put less effort into a task when they see cage-mates receiving tastier treats for completing the same task. But scientists have not felt confident in saying why the poorly rewarded animals slack off.

Some people have suggested the primates that refuse to repeat the task are simply greedy and therefore only willing to work for a bigger reward. Alternately, it has been proposed that the monkeys stop performing the task because they have received large rewards in the past and feel frustrated by the measly amounts offered in later trials.

To understand the monkeys’ reluctance to participate in the task, Frans de Waal at the Yerkes National Primate Research Center in Atlanta, Georgia, US, and colleagues decided to try several variations on this experiment.

Fruits of labour

They trained 13 capuchin monkeys ( Cebus apella ) to retrieve a small rock and place it in the experimenter’s hands. In exchange for completing this task, the animals received a reward.

Pairs of monkeys were seated beside one another in a test booth, separated by a mesh partition. In one trial, the monkeys received the same sized cucumber reward for their efforts and 90% completed the task within 5 seconds.

But then the researchers gave one of the monkeys a grape instead of a cucumber. To a human this may seem like a minor detail, but monkeys go bananas over grapes, which they far prefer to cucumbers.

When the monkeys given cucumber saw their partners receive this grape reward, they invested less effort in future repetitions of the task, and completed it within 5 seconds only 80% of the time.

In a third scenario, the monkeys both received the same cucumber reward, but could see a bowl of grapes just beyond their reach. Under these circumstances, the animals performed the task with the same willingness as when the grapes were hidden. The researchers say that this rules out the possibility that the primates alter their behaviour out of greed.

Species variation

De Waal’s team also found that the monkeys exhibited the same patterns of behaviour regardless of whether they had received a grape or cucumber in preceding experiments, discounting the possibility that the animals slacked off out of frustration from unmet expectations.

They say the study “confirms that capuchin monkeys react negatively to situations in which they receive a less favourable reward than their partner for the same task. Our control procedures suggest that this response was due solely to the discrepancy between the monkey’s own and the other’s rewards and not to individual factors such as greed or frustration.”

Other experts, however, note that earlier studies have shown that monkeys and chimps do not always care about fairness. Keith Jensen at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, recently demonstrated that chimpanzees will accept a rotten deal from a fellow chimp.

Jensen says that understanding how non-human primates view fairness can provide clues about how humans evolved a great capacity for cooperation. But he adds: “Human cooperation is special”.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0707182104)

Sign up to our weekly newsletter

Receive a weekly dose of discovery in your inbox! We'll also keep you up to date with New Scientist events and special offers.

More from New Scientist

Explore the latest news, articles and features

Neolithic engineers used scientific knowledge to build huge megalith

How deadly is mpox and what treatments are available?

DNA computer can play chess and solve sudoku puzzles

Subscriber-only

Our galaxy may host strange black holes born just after the big bang

Popular articles.

Trending New Scientist articles

Survival of the Fairest: Understanding Justice

Experiments show that monkeys have an innate sense of fairness

The next time you feel irritated about getting the short end of the stick, and wonder why it’s so hard to let go of your indignation, watch the YouTube video called “Two Monkeys Were Paid Unequally.” The popular video is an excerpt from primatologist Frans de Waal’s “Moral Behavior in Animals” TED talk. With over 10 million views, the video presents an experiment featuring two capuchin monkeys whose behaviors demonstrate that the drive for fairness is more universal than we thought, extending beyond the human species. The idea for the now-famous experiment arose from the observation of one of de Waal’s students, Sarah Brosnan, while she was working with captive capuchins. She noticed that one of the monkeys would become agitated when it saw another monkey get a better reward for performing the same task. Known as “inequity aversion” in human economics, this behavior prompted Brosnan and de Waal to design an experiment to explore what appeared to be a sense of fairness in these diminutive primates. The capuchins that participated were previously trained to give researchers small stones in exchange for food. During the experiment, the trained monkeys were paired and placed in adjacent cages, so they could see each other. The TED talk video excerpt shows a few rounds of stone-for-food exchanges between the monkeys and a researcher. During the first round, the monkey on the left gives the researcher a stone and in return receives a piece of cucumber, which it readily eats. The monkey on the right then hands over its stone and is given a grape—a food that capuchins greatly prefer to cucumbers—and it happily eats its reward. The interesting thing is that the monkey on the left immediately notices—with a calm curiosity—that its counterpart has received a much better reward for the exact same trade. In the second round, the monkey on the left is once again given a piece of cucumber in exchange for a stone. Even before the monkey on the right makes its exchange for a grape, the left monkey starts to throw a tantrum. It tastes the cucumber, then takes it out of its mouth and throws it at the researcher. It pounds the floor with its fists and rattles its cage. It repeats this same performance in the third round—clearly outraged that it is not getting a grape like the monkey on the right. At this point, most people viewing the video burst into empathic laughter because the monkey’s reaction is so incredibly humanlike. The monkey on the left is clearly getting shortchanged. It is performing the same work as the other monkey—exchanging a stone for food—but isn’t getting the same reward. When it throws the cucumber at the researcher, viewers can’t help but imagine it shouting, “You can take this job and...” Brosnan and de Waal’s experiment showed that monkeys’ sensitivity to fairness was linked to effort. If they did not work (make an exchange) but were given unequal food portions, the monkeys didn’t have negative reactions to any difference in the rations. However, if treats were used as payment for work—for the exchange of the stone—then the capuchins did notice inequities. In fact, the more effort it took to receive the reward, the more sensitive a monkey was to seeing another get something better. Researchers are starting to believe that a sense of fairness is most likely an evolutionary adaptation that developed in certain social species. When discussing the capuchin fairness experiments, for example, de Waal compared the similarity between the responses of the monkeys and chimps to the protesters in the Occupy Wall Street movement: all were objecting to the idea of economic injustice. As de Waal pointed out, if eating were the only thing that mattered, the monkeys would have as readily accepted the cucumber as the grape. But fairness matters, too. Over time, if inequities are allowed to perpetuate they become exploitative and have a detrimental impact on the health of individuals, groups, and perhaps even entire species. So, getting miffed over inequities may be a survival strategy. Perhaps evolution has favored emotions like indignation because it invokes behaviors that foster fairness. And when a species behaves fairly, not only is each individual better off, but the species as a whole is, too.

Bath Bomb: A Fragrant Accessory For Relaxation

Hearty soups for autumn, you may also like, reef revelations, 2023 natural + organic beauty awards, the ultimate guide to vegan beauty, wild beauty, the person of the forest, ocean motion.

TED is supported by ads and partners 00:00

Why monkeys (and humans) are wired for fairness

• decision-making

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Proc Natl Acad Sci U S A
• v.110(Suppl 2); 2013 Jun 18

Justice- and fairness-related behaviors in nonhuman primates

Author contributions: S.F.B. wrote the paper.

A distinctive feature across human societies is our interest in justice and fairness. People will sometimes invest in extremely costly behavior to achieve fair outcomes for themselves and others. Why do people care so much about justice? One way to address this is comparatively, exploring behaviors related to justice and fairness in other species. In this paper, I review work exploring responses to inequity, prosocial behavior, and other relevant behaviors in nonhuman primates in an effort to understand both the potential evolutionary function of these behaviors and the social and ecological reasons for the individual differences in behavior. I also consider how these behaviors relate to human behavior, particularly in the case of experimental studies using games derived from experimental economics to compare nonhuman primates’ responses to those of humans in similar experimental conditions. These results emphasize the importance of a comparative approach to better understand the function and diversity of human behavior.

A feature of humans that apparently sets us apart as a species is our focus on others’ well-being, as well as our own ( 1 , 2 ). We will, sometimes at great personal cost, protest outcomes that we consider unfair, whether they personally affect us or have no direct impact on our lives. What is it that causes people to behave in this way? One possibility is that it is attributable to culture. In fact, only English has a word for the concept of “fairness”; other languages have adopted the English word, indicating a culturally broad interest in the concept but potentially implying that the concept is not ubiquitous ( 3 ). Another possibility is that we have evolved to be interested in the well-being of others. Although there are clear fitness benefits to considering one’s own well-being, there are also (more delayed) benefits to considering others’ well-being. There may be costs to helping others in the short term, but if there are long-term benefits, either because of continued interactions based on reciprocity or, more indirectly, because of gaining a reputation as a “fair” person, then the behavior can be selected ( 4 ). If this behavior has evolved, we may find similar behaviors, or precursor behaviors, in other species. Other species will not show these behaviors in the same way that humans do. Among other reasons for this, many behaviors related to fairness and justice, such as the ability to share information about a third party’s previous behavior, require language. Nonetheless, an important question is the degree to which fairness and justice have evolved from similar sorts of behaviors in other species. This evolutionary approach provides insight into understanding our own behavior.

In humans, the concept of fairness is closely related to that of justice. Distinguishing the two, fairness involves voluntary interactions with other individuals, whereas justice is meted out by an impartial third party ( 3 ). Based on these definitions, most of the experimental work discussed below relates to fairness, rather than justice, because the subjects being studied are involved in the interactions and outcomes in question. Outside of the experimental context, observations suggest impartial interventions in others’ interactions, indicating that these species may also be sensitive to justice concerns. There are many different aspects of justice and fairness, including distributive, procedural, retributive, restorative, etc. Most experimental studies involving nonhuman species measure subjects’ responses to different distributions of food rewards and, hence, concern distributive justice or fairness. In humans, two common distribution mechanisms are egalitarianism, in which all individuals get the same outcome (e.g., equality) and equity, in which individuals’ benefits are proportional to their inputs. Both of these are amenable to study in other species and are the feature most commonly manipulated in the aforementioned experimental studies (e.g., by altering subjects’ payoffs compared with their partner’s). Outside of the experimental realm, observational studies indicate that nonhuman primates are also sensitive to nondistributional aspects of justice and fairness, such as judging the appropriateness of another’s behavior, providing a broader context in which to consider justice or fairness in these species.

Studying other species’ behaviors in these situations allows us to elucidate the evolutionary function of justice and fairness by exploring behaviors that are related, either because the behavior itself is a component of justice or fairness or because it represents a precursor to human behavior. Studying other species is informative in two complementary ways, through homology and convergence. Homologies occur when a behavior exists in multiple species because the behavior existed in a shared common ancestor. This pinpoints when in the taxon’s phylogenetic history the trait evolved. Convergences occur when a behavior evolved in multiple species because of common selective pressures but without shared descent from a common ancestor. Convergences may be particularly informative when studying the function of a behavior because, through comparison across species, they may indicate which traits co-occur and the social or ecological pressures that may have selected for the behavior.

My goal in this review is to bring together data regarding behaviors related to justice and fairness in nonhuman primate species (hereafter, primates). Observations have highlighted situations in which primates act as if their behavior is guided by an interest in the outcomes of others ( 5 ). A decade ago, the first experimental studies emerged, focusing on one aspect of justice and fairness: how individuals responded to getting less than a partner ( 6 , 7 ). These studies used methods derived from game theory and showed that, in experimental settings in which inequity between two individuals was introduced, subjects responded negatively to inequity not in their favor. Since that time, this task has been extended to fourteen species, including 10 primate species, allowing for a broad phylogenetic view that provides insight into the evolutionary function of inequity ( 8 ). Additionally, responses to inequity have been explored in more species-specific contexts and situations ( 9 , 10 ). These results highlight the correlation between inequity and cooperation, as well as emphasizing the socioecological factors that influenced the emergence of justice- and fairness-related behavior. This comparative analysis is beginning to shed light on the factors that may have led to the evolution of justice- and fairness-related behaviors in humans and other primates.

Justice- and Fairness-Related Behavior in Other Species

One hypothesis for the evolution of fairness is that recognizing inequities helped individuals ascertain the value of their partners in cooperative interactions ( 8 , 11 ). Individuals should not continue to work with others if they do not, on average, benefit from the relationship. Whether outcomes are equitable may be used as a proxy; if one’s outcomes are routinely wanting compared with one’s partner’s, then it is likely that an interaction with another partner, even one chosen at random, will lead to a more beneficial outcome. This leads to a partner choice mechanism in which individuals sample other partners when they are experiencing high levels of inequity with the current partner or partners ( 12 ). Note that individuals, thus, recognize and respond to inequity without any understanding of why they are doing so. Additionally, this provides a benefit even if the individual’s outcomes in the less advantageous interaction are net positive, because the currency of natural selection is relative, rather than absolute, gains.

Although this hypothesis linking inequity and cooperation emerged in the context of humans, other species also cooperate with one another, so behaviors related to inequity may occur in other cooperative species as well. Comparative research is challenging. First, the manifestations of justice and fairness may be different in different species, making it difficult for human experimenters to recognize relevant behaviors. Second, nonhuman species are nonverbal, with the dual implications that we cannot ask them about their motivations for their behavior, nor can we ask them about outcomes that did not result in an overt change in their behavior. Thus, we will miss any response that does not have a behavioral manifestation. As a result, experiments focus on whether other species act in a certain way, not whether they mean to act in that way. Finally, the limitation to measuring behavioral changes means that the methods used in humans typically differ substantially from those used in other primates, which can complicate comparative analyses.

There have been two approaches to comparative work on justice and fairness. The first is to adapt game theory methods to explore decision-making in other species. Game theory is a powerful approach that allows complex decision-making to be modeled experimentally as a series of carefully controlled choices, which can be experimentally manipulated to rigorously explore the behavior of interest ( 13 ). The advantage of game theory for comparative research is the focus on very simple choices to uncover complex behavior, making these techniques amenable to use in a wide variety of other species. Procedures can be designed that require no verbal instruction whatsoever and that can be used in the same form in humans and other species, allowing for direct comparisons and subsequent explorations of shared outcomes or cognitive mechanisms ( 14 ). Although we cannot assume that different species (or different individuals within the same species) interpret identical procedures in the same way, if procedures differ between species, then we are never able to disentangle whether any resulting differences in behavior are attributable to species differences or differences in the procedure. One challenge to experimental approaches is that humans interact with an experimenter of the same species, whereas other species interact with an experimenter of a different species (a human). Although this is a practical necessity, other species did not evolve to interact with humans, and so careful controls are needed to determine that the nonhuman subjects were evaluating their outcomes relative to their conspecific partner, not the experimenter or another aspect of the environment. Additionally, experimental approaches are artificial, and so we may miss situations in which justice-related behavior occurs. Despite these drawbacks, game theoretic approaches have the advantage of being comparable to the human literature and so are indispensable for comparative research.

A second approach is to explore behaviors that may be related to justice and fairness in species-specific contexts. This includes observational studies, in which behavior is observed during unconstrained interactions. This approach has the advantage of being the most natural, which leads to likely candidate behaviors and a better understanding of how justice or fairness manifest in the species’ typical interactions. Moreover, because these studies are not reliant on manipulating outcomes and measuring subjects’ subsequent behavior, there is the opportunity to study justice outside of the context of food distributions. The disadvantages are that these results are less comparable across species, particularly if methods or the contexts in which individuals are attentive to inequity differ, and the underlying motivations for subjects’ behavior are not known. The ideal is to combine insights from both approaches.

Using Game Theory to Explore Justice-Related Behavior

The ultimatum game..

In 1982, Werner Guth presented the Ultimatum Game (UG), designed to explore fairness in bargaining behavior in humans ( 15 ) ( Fig. 1 ). In this game, one individual, a proposer, is given a set sum and told to allocate it between him or herself and a partner. If the partner, called the responder, accepts the allocation, both parties receive the money as allocated, but if the responder rejects it, neither party receives anything. Hundreds of experiments across the last three decades have shown that modern Western humans typically allocate about 40% of the sum to the responder, and responders typically reject any offer under about 20% of the allocation ( 16 ). Allocations are higher than those seen in a related game, the Dictator Game (DG), in which the responder has no recourse to the proposer’s allocation, indicating that the proposer alters his or her allocations dependent upon whether the responder can influence the outcome.

Schematic diagram of the UG.

The UG is often considered to measure fairness preferences; thus, it is particularly relevant to considerations of fairness and justice in other species. There have been two studies in chimpanzees, both relying on a limited-form version of the game in which proposers make a choice from between two preset distributions. In neither case did chimpanzee responders refuse allocations; however, proposers’ behavior differed between the studies. In the first, proposers chose between the two trays, each of which contained foods for them and their partner (neither chimpanzee could reach their partner’s food). After the proposer chose one option, by pulling the corresponding tray within reach of the responder, the responder could choose whether or not to accept the offer by pulling the tray in such a way that both the proposer and the responder could access their rewards. In this study, proposers consistently chose the larger outcome for themselves and responders accepted virtually any offer ( 17 ). However, responders accepted more than half of zero offers (e.g., they received nothing themselves), indicating that they may not have understood the task. A subsequent study showed that human responders rarely refused in a similar situation ( 18 ), indicating that the deviation from behavior typically seen in the UG could have been attributable to the experimental design.

In a more recent study ( 19 ), subjects were trained that one token represented an equal 3/3 split of six food items, whereas the other represented a 5/1 split of the foods in favor of the proposer. Proposers could choose a token and pass it to the responder, who could then trade it out to the experimenter (accepting the proposal) or not (refusing it). Proposers’ choices in the UG were compared with those in a DG-like condition in which the responder was present but had no recourse (proposers passed the chosen token directly to the experimenter). The procedure was repeated using children paired with another familiar individual from their daycare class to ensure that humans would respond similarly to chimpanzees in this procedure.

Despite responders never refusing offers, all chimpanzee proposers’ choices shifted from preferring the more beneficial 5/1 token in the DG-like condition to preferring the equal 3/3 split in the UG. Validating the procedure, children responded in the same way. These results differ from typical UG results because neither the children nor the chimpanzees ever refused the low offer. However, in typical human UGs, responders are interacting with anonymous partners, and their only recourse is to refuse the offer. In this study, responders were interacting with individuals from their social group and had options besides refusal, such as punishment or the threat of punishment, which are less costly means of protest than refusing a positive, if relatively smaller, outcome ( 20 ). Similarly, in typical UGs, proposers’ refusals decrease when they are given other options [e.g., the responder can write a note to the proposer ( 21 )]. These results do not necessarily mean that the chimpanzees showed a sense of fairness, because if this were this the case, they should have preferred the equal token in both the DG and the UG conditions. This also does not mean that proposers had prosocial motivations, because they may have changed their preference to avoid refusals by the responder. Nonetheless, both humans and chimpanzees were apparently sensitive to how their choices influenced their partner’s decisions and changed their behavior accordingly.

The Impunity Game.

Closely related to the UG is the Impunity Game (IG) ( Fig. 2 ). The IG is similar to the UG, but if the responder refuses the proposer’s offer, the responder gets nothing, whereas the proposer receives their portion of the allocation as indicated by the proposer ( 22 ). This game has received very little attention in the human literature. In part, this is due to the assumption that no rational responder would ever refuse an offer, because this action leaves them with both absolutely and relatively less than the proposer (in the UG, a refusal leaves the responder with absolutely less but relatively the same as the proposer). Nonetheless, in a study that used the same procedure for both games, human subjects refused in the IG about half as often as in the UG for a given distribution ( 23 ).

Schematic of the IG. The full IG has not yet been explored with other species; however, a typical inequity procedure is reminiscent of the responder’s choice in the IG (indicated by the dotted line).

Much as in the UG, the challenge of the IG with primates is assuring that the responders understand that their choice was constrained by the actions of the proposer. Most studies of primates to date have explored only responses to unequal distributions, to learn how individuals respond to inequity when they cannot alter their partner’s outcomes (reviewed in ref. 24 ). In a typical experiment, paired subjects alternate completing a task (such as exchanging a token) with a human experimenter. The experimenter rewards subjects with the same rewards (Equity condition) or gives one a more preferred reward (Inequity condition). To rule out the possibility of contrast effects ( 25 , 26 ), in which subjects compare their outcomes to those present in the environment without attending to the social component, pairs are given a Contrast condition, in which both partners are shown the preferred reward but, after completing the task, receive the less-preferred one ( 27 , 28 ). These responses are referred to as Inequity and Equity rather than Inequality and Equality because, despite the fact that the outcomes are identical (or not), we cannot know whether they are perceived identically by subjects because of differences in rank, hunger level, etc.

Initial studies confirmed that both capuchin monkeys ( 6 , 29 , 30 ) and chimpanzees ( 7 , 28 ) were more likely to refuse to complete the interaction (e.g., return the token or accept the subsequent food reward) in the Inequity condition compared with either the Equity condition or the Contrast condition, although there was variation within and between studies [discussed below in more detail ( 7 , 31 , 32 )]. Because humans refuse more frequently in situations in which they do not like the outcome (e.g., in the UG game), this similar behavior in other species has been interpreted as responding negatively to inequitable outcomes. The response is also sensitive to context, with refusals occurring only after subjects have completed a task but not when rewards are simply handed out for “free” ( 26 , 32 – 35 ). Despite this, subjects do not change their rate of refusal when they have to work harder than a partner to achieve their reward (ref. 36 , but see ref. 37 for an exception). This indicates that although subjects are sensitive to inequity in the context of joint action, it is the difference in outcome rather than effort that is important for their decision-making. This may indicate that subjects are more sensitive to distributional inequities than procedural ones.

Demographic variables also influence individuals’ responses, but not always in consistent ways. For instance, not all studies show a dominance effect, although for those that do, dominant individuals always respond more strongly than do subordinates, presumably because they are more accustomed to receiving higher-valued rewards ( 28 , 31 ). There are also no consistent sex differences ( 7 , 28 ), possibly because of relatively small sample sizes (although several dozen chimpanzees have been tested across three facilities, a large sample for captive primate studies, this is a very small sample size for untangling individual variation). The degree to which individual differences influence behavior—both in nonhuman and human primates—is a topic that requires additional exploration.

Finally, not all primate species refuse in conditions of inequity. The same procedure to elicit inequity has now been used to test seven primate species, and similar procedures have been used with several others ( Table 1 ). Comparing these different species’ responses allows us to consider which social or environmental factors may have played a role in shaping the evolution of the response. Although more species will need to be tested to verify these conclusions, patterns are emerging. For instance, responding negatively to inequity is not a homology within the primates. Among the great apes, bonobos may respond similarly to chimpanzees and humans, indicating that the last common ancestor of Pan and Homo shared this behavior. Only five bonobos have been tested, making statistical analyses difficult; however, their refusal rates doubled from 10 to 20% in the Inequity compared with the Equity condition ( 31 ). On the other hand, orangutans showed no response to inequity ( 31 , 38 ), eliminating the possibility of a homology within the great apes. Additionally, the behavior is not a homology within the New World monkeys, because of the five New World monkeys tested, only capuchins responded differently to the inequity condition. The orangutan’s behavior also rules out the possibility that this is related to increased brain size or advanced cognitive capabilities, because orangutans have a similar brain-to-body ratio and cognitive skills as the other great apes.

Summary of inequity studies by species, including whether inequity aversion has been found with different methods and the influence of effort and social context

Dashes indicate that no study has yet been done on the topic. Adapted from Price and Brosnan ( 24 ) with permission from Springer Science+Business Media B.V.

Thus far, negative responding to inequity correlates positively with whether a species cooperates routinely with nonkin (reviewed in ref. 8 ) ( Fig. 3 ). Chimpanzees, bonobos, and capuchin monkeys cooperate with nonkin, for instance in coalitions and alliances, and all three species responded to inequity in these experiments. Macaques, too, both responded negatively to inequity ( 39 , 40 ) and showed cooperation in the form of coalitions and alliances ( 41 ). However, in squirrel monkeys, a species confamilial (and sympatric) with capuchins but lacking extensive social cooperation, males responded more strongly to the Contrast condition than either the Inequity or Equity conditions, indicating that their reactions were more strongly influenced by their previous offers than by rewards received by another monkey ( 27 ). Again considering orangutans, one way in which they differ from chimpanzees and bonobos is their relative lack of social cooperation. A potential difficulty arises with the species that show biparental care. These species cooperate extensively, working together to raise offspring, but thus far there is no indication that such species respond negatively to inequity in this experimental paradigm ( 34 ). However, the proposed function of responding to inequity is to judge the value of cooperative partners to determine whether to search for a new partner. It is very costly to find a new pair mate, so it is possible that even if individuals in biparental care species do notice inequities, they have evolved to respond only to large inequities, which does not include receiving a less-preferred reward than their mated partner.

Schematic diagram indicating the responses to inequity of species that have been tested using the typical inequity procedure in which subjects exchange tokens for rewards while sitting next to a partner. The photos representing species that show a negative response to inequity in this task are outlined in green, and those that do not are outlined in red. The names of species that show extensive social cooperation, such as coalitions and alliances, are in green, those that do not are in red, and interdependent species (e.g., with biparental care) are in violet. Humans show both extensive social cooperation and biparental care. Note that this diagram excludes gorillas, for whom too little information is known. The photographs of the macaque and bonobo are by F. B. M. de Waal. The photograph of the orangutan is by C. Talbot. The photograph of Darwin is from the public domain. All other photographs are by the author.

Related to this, subjects should be more sensitive to inequity when forming a relationship, which is a time when the costs of finding a new partner are less, than after the relationship is established and there is joint investment in offspring ( 8 ). One drawback to our understanding of human behavior is that most studies to date have involved unrelated individuals, mostly strangers, virtually always in conditions of anonymity, and often without repeated interactions, which removes the possibility of reputations forming. Although these conditions are informative for exploring the degree to which humans will cooperate without either a relationship or social knowledge, this is not as informative for telling us about typical human cooperative behaviors, which primarily take place within established relationships with known partners. Additional experiments that explore differences in behavior in the context of different social relationships and with different degrees of anonymity will be essential to understand how inequity functions in the context of the relationship.

Prosocial Games.

Despite children’s calls of “that’s not fair” when they receive a less-preferred outcome than another child, responding negatively to receiving less than one’s partner is only one part of a sense of fairness. A sense of fairness or justice requires responding not only to inequities that affect oneself but also to those that affect others ( 11 , 42 ). This has been experimentally explored most commonly using procedures reminiscent of the Dictator Game. In the typical experimental game with primates, the subject has the option to provide rewards, or not, to a social partner. Importantly, the subject’s behavior with a social partner is compared with their behavior when alone, ruling out the possibility that they are choosing the prosocial option because there are a greater number of rewards visible than in the nonprosocial option. The critical difference between these games and the DG is that choosing to reward the partner does not reduce the subject’s own payoffs in these prosocial games; thus, there are no disincentives for prosocial behavior.

Although reward structures have varied across experiments, making direct comparisons difficult, a sufficient number of these studies exist that patterns are emerging. Chimpanzees choose to bring rewards to their partners in some experiments ( 43 ) but not others ( 44 , 45 ), and it is not yet clear which features lead to prosocial behavior in this ape. It is also not clear that these results are reflective of chimpanzees’ prosocial tendencies. Results in the inequity studies described above imply that chimpanzees may recognize when they receive a better outcome than a partner even when they chose not to act to change the situation. In these studies, subjects sometimes refused preferred rewards when their partners got less-preferred ones and did so at greater rates than when both received preferred rewards ( 28 ). This does not mean that the subject’s motivations were prosocial, because they may have feared the partner’s reaction to receiving a less-preferred reward than the subject, but these results verify that chimpanzees recognized when they received better outcomes than a partner.

Among the monkeys, capuchin monkeys preferentially chose the prosocial option ( 46 , 47 ) and were more likely to reward kin than either nonkin group mates or nongroup mates ( 46 ). Callithrichids, one of the taxa that show biparental care, also chose the prosocial option that rewarded a group mate ( 48 , 49 ), although like the chimpanzees, they did not do so in all experiments ( 50 ). Finally, long-tailed macaques also showed prosocial behavior, but in this study, dominants chose the prosocial option, whereas subordinates did not ( 51 ). Again, these studies measured behavior, not motivations, so they cannot shed light on why the monkeys behaved prosocially (e.g., they cannot disentangle whether subjects were prosocially motivated to help their partners or were selfishly motivated to avoid repercussions for not helping their partners). Nonetheless, although there is still debate about the contexts under which each of these species show prosocial behavior and the selective pressures underpinning it, in some circumstances, all of the primates tested thus far actively chose an outcome that benefitted a partner as well as themselves.

Species-Specific Approaches to Justice and Fairness

Inequity in the context of cooperation..

If responding to inequity is a mechanism for identifying good cooperative partners, then inequity should influence behavior when cooperation is required. This can be experimentally explored by introducing inequity into an experimental cooperation paradigm. Capuchin monkeys have been studied extensively in the realm of cooperation, and there is evidence that they understand the contingencies of cooperative tasks and are sensitive to their partner’s behavior (reviewed in ref. 52 ). In the first study to explore cooperation in a situation of inequity, capuchin monkeys could work together to pull in a heavy tray to obtain food, but only one monkey got the food. Monkeys worked together, but only if the individual who received the food shared with the individual who did not. Perhaps anticipating this, the monkey who got the food was more likely to share in this condition than in a control condition in which they could acquire the food without their partner’s help. This indicates a sensitivity to their partner’s reaction and an anticipation of their need for their partner’s help ( 10 ).

In a study more explicitly exploring inequity and cooperation, monkeys were tested in a similar paradigm in which both monkeys always received food, but these foods differed in the degree to which the monkeys preferred them. Thus, sometimes both monkeys received the (same) preferred food, sometimes they received the (same) less-preferred food, and sometimes one received the preferred food, whereas the other received the less-preferred food. The monkeys were not separated nor were their roles predetermined by the experimenter, so in all cases, the monkeys had to negotiate between themselves who would pull from which location, which also determined who got which food item. The pair’s pulling success was not dependent upon the value of the rewards; pairs pulled in the tray just as often for two identical rewards as for two different ones. Instead, the monkeys were sensitive to their partner’s behavior. In some partnerships, individuals shared access to the more preferred reward when the rewards differed, each receiving it approximately half of the time. In these partnerships, cooperative pulling success was high (∼70%) in all three conditions. On the other hand, for partnerships in which one member dominated the preferred reward in the different-reward condition, they succeeded in pulling in the tray only about 30% of the time across all three conditions ( 9 ).

These results show two important things. First, subjects in the inequitable partnerships apparently reacted against their partner, not the reward distribution. That is, when one member dominated the preferred reward in the different-reward condition, pulling rates dropped across all conditions, even the two conditions in which both monkeys got the same reward. This supports the hypothesis that recognizing inequity helps to identify cooperative partnerships, because these subjects refused to work with a specific partner rather than refusing a certain outcome. Second, in the partnerships in which neither individual dominated the preferred rewards, subjects were, by definition, receiving the less-preferred reward on half of all different-reward trials, and yet cooperation was maintained. The reality of cooperation is that it is unlikely that every individual will receive the same reward on every trial, and these results indicate that capuchins are somehow able to extrapolate across multiple trials and therefore reap the gains of cooperation despite variation in outcome.

Inequity in Interactions with the Experimenter.

Although the above data relate to primates’ rewards in comparison with each other, how do primates react toward the experimenter who caused the inequity? A recent study explored which of two novel experimenters the monkeys preferred to interact with in a task in which the monkey returned a token to an experimenter to get a food reward. Subjects first gained experience with both experimenters, one of whom consistently provided the offered rewards and one of whom failed to provide the offered reward (or any reward) on up to 50% of trials. When the monkeys then had free choice as to which experimenter they would return the token to, subjects were equally likely to interact with both experimenters ( 53 ). Although it may be that capuchin monkeys do not form preferences for experimenters based on reliability [they do show preferences between experimenters in other situations ( 54 )], it is also possible that the relationship between humans and captive nonhuman primates influenced the results. Despite the fact that subjects in ref. 53 had never interacted with the experimenters who participated in the study, they did have extensive experience with experimenters in general, as well as with trials in which rewards were not given (e.g., because of incorrect responses). Thus, they may have responded to this situation by trying to “correct” their response, rather than recognizing the experimenter’s unreliability. Pet dogs, who may have a different relationship with humans, do discriminate between human experimenters in a similar task ( 55 ).

Inequity in Social Interactions.

Some of the best evidence in favor of a sense of justice or a sense of fairness comes from observational studies of nonhuman primates’ interactions during their natural behavior. These interactions also offer the opportunity to look beyond distributional equity. Unfortunately, in many cases, these events are extremely rare, making it difficult to make strong statements about these behaviors. Moreover, observational work yields correlations, which cannot tell us causation without controlled studies that alter one variable at a time. Nonetheless, these situations may be the best window we have into primates’ sense of fairness and justice because they are natural interactions, unconstrained by interactions with humans or experimental contingencies.

Chimpanzees display a sense of “social regularity” that has been linked to the human sense of justice ( 5 ). Chimpanzees appear to have expectations about others’ behavior and are known to express frustration, sometimes aggressively, when these expectations are violated. Moreover, such responses are not limited to the apes. Apes and monkeys both engage in policing behavior in which individuals, typically the highest-ranking males, intervene in fights to maintain group stability. Some of the best evidence for the utility of policing behavior comes from studies done with macaques. In these studies, the group's behavior was compared on typical days and those in which the highest ranking males were removed. Results demonstrated the males’ necessity in stabilizing the group’s interactions ( 56 , 57 ). Similarly, both macaque and chimpanzee males, once they have established high status, will intervene in fights on the side of the loser ( 58 , 59 ). Although there are many reasons for such behavior, it again indicates that these males recognized social inequalities in others’ interactions and were willing to act against their own short-term self interest to rectify them. Of course, in the longer term, maintaining group stability always benefits a high-ranking male, and a physical intervention may additionally emphasize his power to others in his group. Nonetheless, there are short-term costs to entering into any fight, particularly in favor of an individual who is losing.

Recently, inequity has also been linked with play fighting in gorillas. Gorillas who gained the upper hand during a bout of play fighting worked to maintain it, possibly indicating that they were aware of the social dynamics and strove to maintain their competitive advantage ( 60 ). The authors emphasized the benefit of studying inequity in a natural social context and considered how responses to inequities may vary depending on whether the individual in question has the social advantage. Again, for practical experimental reasons, much work focuses on inequity of food rewards, but attention to inequity may have evolved in the social realm and only more recently adapted to physical outcomes, such as food. Future work will help to determine how responses to inequity vary depending upon the commodity in question.

Inequity and Related Behaviors

Inequity likely interacts with other behaviors, although, thus far, there have been few studies to explore these interactions.

Punishment.

Recognizing inequity is only one of several behaviors that likely underpin cooperation. Punishment may also support cooperation. Cleaner fish, which cooperate with nonkin during the cleaning interaction, do not respond to inequity of rewards compared with a social partner ( 61 ). However, the fish do punish one another for acting against the pair’s interests ( 62 ). Thus, it may be that in species or situations in which finding a new partner would be difficult or costly, punishment to change the current partner’s behavior is used in lieu of finding a new partner ( 63 ).

Inequity and Contrast Effects.

It seems likely that responses to inequity share cognitive mechanisms with behaviors such as loss aversion and contrast effects, both of which involve reactions to unexpectedly lesser outcomes. These are rather difficult to untangle experimentally, given that inequity is essentially a contrast effect with another's outcome as the referent (similarly, inequity is a loss with another's outcome as the referent). However, we can compare the relative strengths of these motivations using well-designed experiments. For instance, whereas some species (e.g., chimpanzees and capuchin monkeys) were more sensitive to inequity with one’s partner than to contrast with previously offered outcomes, others (e.g., squirrel monkeys) showed the reverse. Mapping such preferences may help to determine the underlying influences on the expression of these behaviors, providing insight into the relative strength of social and nonsocial environmental stimuli on a species’ decision-making.

Future Directions and Conclusions

Although in the previous decade we have learned much about nonhuman primates’ responses to inequity, there remains much to learn. First and foremost, humans are primates, which makes nonhuman primates a natural group for comparison, yet other species also respond to inequity ( 55 , 61 , 64 , 65 ). More work is needed to identify which species respond to inequity, whether these responses are similar across species, and the nature of individual differences in response in these species. This will also provide a stronger test of the hypothesis that inequity responses correlate with cooperation.

Another important area of inquiry is distinguishing situations in which nonhuman species notice versus respond to inequity. All of the studies described above focus on behavioral responses to differing outcomes, but subjects may notice an inequitable situation that they do not to respond to, for instance, because they are unable to inhibit their desire for the reward, because of social pressure, or for other reasons not yet known. One way to address this question is to explore changes in individual’s affect across different conditions to identify responses that occur in the absence of an overt behavioral change. This approach has been successful in identifying recognition of inequity in young children ( 66 ).

Inequity also occurs in a variety of contexts that are not yet reflected in the nonhuman literature because of the focus on distributional concerns in experimental tests. One major focus of human research that has received little attention in the nonhuman literature is procedural inequity ( 67 ). Although preliminary investigations reveal no change in subjects’ behavior based on procedural variations ( 28 ), nonhuman primates have expectations about others’ behaviors and it is reasonable to assume that they are sensitive to procedural differences.

All of the experimental work to date has involved an egocentric approach to fairness and justice, yet observational studies of natural behavior indicate that primates will intervene in the interactions of others, in some cases impartially. Although challenging, it is possible to study fairness in the laboratory removed from egocentric reactions. Experimental studies on reputation in chimpanzees indicates that these apes are able to form opinions about human experimenters from watching these experimenters interact with other chimpanzees ( 68 ). A fruitful line of inquiry would be to explore nonhuman primates’ judgments of the equity of others’ interactions. Such third-party assessments of others’ distributions would be the first research to experimentally examine justice in other species.

Finally, studies of justice and fairness will advance significantly when work from the laboratory is combined with what we know about animals’ natural behaviors in the wild. In this way, we will better understand the social and ecological conditions under which these preferences manifest, which lends additional insight into their function. Additionally, combining these behavioral studies with what we know about cognition may yield insights in to these behaviors, such as the overlap between inequity and delay of gratification ( 24 ).

Humans are not alone in responding negatively to differential treatment compared with a partner. This response is shared with other species and appears to be instrumental in successful cooperation. Understanding the evolution of this response provides insight into our own behavior. Although nonhuman primates do not show a sense of justice or fairness in the same way as humans do, gaining knowledge about the evolution of justice and fairness from comparative studies will improve our understanding of these judgments in humans as well.

Acknowledgments

I thank L. Salwiczek for helpful comments on an earlier draft of this manuscript. Funding was provided by National Science Foundation (NSF) Faculty Early Career Development Award SES 0847351 and NSF Grant SES 1123897.

The author declares no conflict of interest.

This paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “In the Light of Evolution VII: The Human Mental Machinery,” held January 10–12, 2013, at the Arnold and Mabel Beckman Center of the National Academies of Sciences and Engineering in Irvine, CA. The complete program and audio files of most presentations are available on the NAS Web site at www.nasonline.org/evolution_vii .

This article is a PNAS Direct Submission.

Study: Monkeys Have Sense of Justice

Sept. 18 -- It turns out monkeys, like people, are no fools when it comes to equal pay for equal work.

A new study found when brown capuchin monkeys noticed their partners were getting a better reward — a juicy grape — for the same task, and sometimes for no task at all, they became indignant.

The results suggest people and monkeys may have inherited a sense of justice over the course of evolution and it is not something humans simply learn from society.

"There's a theory that people who have a sense of fairness are more likely to cooperate," explained Sarah Brosnan, a researcher at Emory University in Atlanta, Ga. whose study appeared this week in the journal Nature. "We know that capuchins cooperate and we wanted to find out if fairness mattered."

It mattered.

Sour Grapes

In the tests, Brosnan and her colleague, Frans de Waal, handed monkeys a granite stone in the presence of another monkey. The monkeys were trained to then return the stone in exchange for a reward.

If both monkeys got a cucumber slice in return, the animals completed the trade 95 percent of the time. But if one monkey got a grape while the other received a lesser reward of a cucumber chunk, the slighted animal would cooperate only 60 percent of the time. Sometimes it would refuse the cucumber or turn its back to their human subject.

If the animal's partner received a grape without even having to carry out a trade, the partner who had to complete the trade for a cucumber became even more annoyed and cooperated only 20 percent of the time. In some cases, the monkey would throw its cucumber slice back at the human testers.

"It's hard to judge the emotions of non-human animals — you can't ask them," said Brosnan. "But they did show signs of what might be frustration — it's highly unusual for a capuchin to turn down food."

Brosnan used five female monkeys for the study since female capuchin monkeys live in groups in tropical forests and depend on cooperation to share food. Male capuchins, meanwhile, generally live on their own or as alpha males ruling over a group of females.

Trending Reader Picks

Pilot who tried to shut down engines shares story

• Aug 23, 6:10 AM

Will RFK Jr.'s endorsement give Trump momentum?

• Aug 23, 6:32 PM

Trump responds angrily to Harris DNC speech

• Aug 23, 12:34 AM

Free at-home COVID tests program to restart

• Aug 23, 1:36 PM

JD Vance pushes for 1M deportations

• Aug 11, 9:00 AM

ABC News Live

24/7 coverage of breaking news and live events

Stack Exchange Network

Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Was the experiment with five monkeys, a ladder, a banana and a water spray conducted?

I've found the following picture online. It is about the moral/paradigm behind consistent behavior.

Click to enlarge.

The image text says

A group of scientists placed 5 monkeys in a cage and in the middle, a ladder with bananas on the top. Every time a monkey went up the ladder, the scientists soaked the rest of the monkeys with cold water. After a while, every time a monkey went up the ladder, the others beat up the one on the ladder. After some time, no monkey dare[d] to go up the ladder regardless of the temptation. Scientists then decided to substitute one of the monkeys. The 1 st thing this new monkey did was to go up the ladder. Immediately the other monkeys beat him up. After several beatings, the new member learned not to climb the ladder even though he never knew why. A 2 nd monkey was substituted and the same occurred. The 1 st monkey participated on [ sic ] the beating for [ sic ] the 2 nd monkey. A 3 rd monkey was changed and the same was repeated (beating). The 4 th was substituted and the beating was repeated and finally the 5 th monkey was replaced. What was left was a group of 5 monkeys that even though never received a cold shower, continued to beat up any monkey who attempted to climb the ladder. If it was possible to ask the monkeys why they would beat up all those who attempted to go up the ladder ... I bet you the answer would be ... "I don't know — that's how things are done around here" Does it sound familiar? Don't miss the opportunity to share this with others as they might be asking themselves why we continue to do what we are doing if there is a different way out there.

This seems like an experiment, but now I'm wondering... Was this experiment ever conducted? If not, was any similar experiment conducted that shows the same effect?

• 13 There were several positive negative reinforcement experiments performed but this sounds like an extrapolation of predicted results combined with humanized responses. This story makes it sound like negative reinforcement alone can trigger this powerful anti social group behavior. Its a myth –  Chad Commented Nov 4, 2011 at 18:31
• 16 You are probably anyway not allowed to do this kind of tests on monkeys any more. Nowadays you would need to use interns etc. –  Martin Scharrer Commented Apr 12, 2012 at 9:16
• 34 You need ten monkeys. . . –  Rory Alsop Commented Mar 28, 2013 at 13:27
• 33 Actually they seem to me like pretty darn smart monkeys. This effect is how humans avoid many dangers to astonishing levels of reliability, like traffic, poisonous berries, bad puns, and esoteric discussions. Oh wait. –  Bob Stein Commented Jul 26, 2013 at 10:53
• 23 What @BobStein-VisiBone said. This story is told to show how people follow traditions mindlessly. But the monkeys are helping each other avoid a bad outcome. The consequences may be capricious (the researchers could stop spraying water), but the monkeys don't know that. If the contraindicated activity were eating poisonous mushrooms, we wouldn't think the monkeys were clever for occasionally eating some to make sure they were still lethal. Perhaps the real message of this thought experiment is that a tradition can have a good reason behind it, even if we've forgotten what that reason is? –  Kyralessa Commented Jan 21, 2016 at 0:42

2 Answers 2

The earliest mention I could find of this experiment was in the popular business/self-help book, Competing for the future by Gary Hamel and C. K. Prahalad (1996). Here is the quote from the book:

4 monkeys in a room. In the center of the room is a tall pole with a bunch of bananas suspended from the top. One of the four monkeys scampers up the pole and grabs the bananas. Just as he does, he is hit with a torrent of cold water from an overhead shower. He runs like hell back down the pole without the bananas. Eventually, the other three try it with the same outcome. Finally, they just sit and don’t even try again. To hell with the damn bananas. But then, they remove one of the four monkeys and replace him with a new one. The new monkey enters the room, spots the bananas and decides to go for it. Just as he is about to scamper up the pole, the other three reach out and drag him back down. After a while, he gets the message. There is something wrong, bad or evil that happens if you go after those bananas. So, they kept replacing an existing monkey with a new one and each time, none of the new monkeys ever made it to the top. They each got the same message. Don’t climb that pole. None of them knew exactly why they shouldn’t climb the pole, they just knew not to. They all respected the well established precedent. EVEN AFTER THE SHOWER WAS REMOVED! ( Source )

The authors did not provide a source for this claim. This story was later repeated in various other popular business/self-help books.

Every source online I could find erroneously attributed the experiment to one of the above authors. No one, anywhere , seems to have a reference to the actual experiment.

C. K. Prahalad is deceased, but Gary Hamel is still alive. I tried contacting him several times, but unfortunately both he and his secretary were very evasive. The best I could get was

Our apologies, but Professor Hamel does not have the original source information at hand in terms of your request.

Given that there seems to be no evidence anywhere of this experiment ever actually taking place, that all trails of references eventually lead to the claim in this book, and that this is the earliest available mention of the experiment, until further evidence becomes available the most reasonable conclusion is that C. K. Prahalad or Gary Hamel made up the experiment for their book.

Even if the above authors were not the creators of the myth, there is still reason to believe that, as @Chad puts it (comments above), this claim is an "extrapolation of predicted results combined with humanized responses."

Here is a quote from an "anthropology professor who's worked with hundreds of monkeys over the last 30 years." When asked what he thought of the experiment, he responded succinctly with:

If you have bananas on a pole, you'll lose your bananas.

• 27 That last quote is interesting, I'm still wondering what Gary Hamel has to say about that. –  Tamara Wijsman Commented Nov 4, 2011 at 21:06
• 5 @Tom: see edit. I've given up trying to contact him. Perhaps if more people ask , we can get a better response. –  BlueRaja - Danny Pflughoeft Commented Nov 28, 2011 at 18:47
• 226 Followup question: if 4 more people replied that it's not a real experiment, would the next person reply without even bothering to do the research? –  JeffSahol Commented Aug 5, 2013 at 17:58
• 17 The human version of this experiment: en.wikipedia.org/wiki/Asch_conformity_experiments –  Pacerier Commented Jul 3, 2015 at 10:59
• 50 It's not a real experiment. Source: everyone else told me it wasn't real when I got here. –  Dan Henderson Commented Oct 11, 2015 at 16:47

TL;DR: It sounds like a similar monkey experiment did take place, and the results were similar to that presented in the picture, but if this is the same experiment, most of the details are wrong.

The first google result for monkeys ladder experiment contains to the following information:

Stephenson (1967) trained adult male and female rhesus monkeys to avoid manipulating an object and then placed individual naïve animals in a cage with a trained individual of the same age and sex and the object in question. In one case, a trained male actually pulled his naïve partner away from the previously punished manipulandum during their period of interaction, whereas the other two trained males exhibited what were described as "threat facial expressions while in a fear posture" when a naïve animal approached the manipulandum. When placed alone in the cage with the novel object, naïve males that had been paired with trained males showed greatly reduced manipulation of the training object in comparison with controls. Unfortunately, training and testing were not carried out using a discrimination procedure so the nature of the transmitted information cannot be determined, but the data are of considerable interest.

Sources: Stephenson, G. R. (1967). Cultural acquisition of a specific learned response among rhesus monkeys. In: Starek, D., Schneider, R., and Kuhn, H. J. (eds.), Progress in Primatology, Stuttgart: Fischer, pp. 279-288.

Mentioned in: Galef, B. G., Jr. (1976). Social Transmission of Acquired Behavior: A Discussion of Tradition and Social Learning in Vertebrates. In: Rosenblatt, J.S., Hinde, R.A., Shaw, E. and Beer, C. (eds.), Advances in the study of behavior, Vol. 6, New York: Academic Press, pp. 87-88.

The above quote is found on page 88 of the 1976 document quoted above .

It is possible the claim is referring to this experiment, with diverging details, or that another experiment took place that was closer to the details in the claim.

• 15 @BlueRaja-DannyPflughoeft, after reading the paper link bellow, it does look like the beginning of the described experiment; learning passed on. It does fail to join all subjects that haven't interacted with the object and have them pass their knowledge to their fellow kin. I would say the folloing 'anecdote' uses the basis for this experiment and greatly builds upon it. The answer to the OP would be NO, it hasn't. scribd.com/doc/73492989/… –  Frankie Commented Apr 15, 2013 at 18:30
• 4 Stephenson's paper: erikbuys.files.wordpress.com/2012/04/… . –  amoeba Commented Sep 14, 2017 at 9:41

You must log in to answer this question.

Not the answer you're looking for browse other questions tagged psychology behavior memory morality ..

• Featured on Meta
• Bringing clarity to status tag usage on meta sites
• We've made changes to our Terms of Service & Privacy Policy - July 2024
• Announcing a change to the data-dump process

Hot Network Questions

• Will this be the first time, that there are more People an ISS than seats in docked Spacecraft?
• Unsupervised classifier, no data in training input
• What do the hexadecimal numbers represent on the ls output of the /dev directory?
• Can figere come with a dative?
• How can I address my colleague communicating with us via chatGPT?
• How can one says that a particle IS a representation of some group?
• Why if gravity were higher, designing a fully reusable rocket would be impossible?
• What does 北渐 mean?
• How to extract code into library allowing changes without workflow overhead
• What is the difference between an `.iso` OS for a network and an `.iso` OS for CD?
• How did the cop infer from Uncle Aaron's statement that Miles has been visiting?
• Are Experimental Elixirs Magic Items?
• Idiomatic alternative to “going to Canossa”
• What Christian ideas are found in the New Testament that are not found in the Old Testament?
• Can the speed of light inhibit the synchronisation of a power grid?
• When a submarine blows its ballast and rises, where did the energy for the ascent come from?
• Fast circular buffer
• Jacobi two square's theorem last step to conclusion
• Miracle Miracle Octad Generator Generator
• Everyone hates this Key Account Manager, but company won’t act
• Vector of integers such that almost all dot products are positive
• Can you successfully substitute pickled onions for baby onions in Coq Au Vin?
• Does gluing two points prevent simple connectedness?
• How to calculate APR and amount owed

Is it time to end biomedical experiments on monkeys?

Some researchers argue testing on primates is both unethical and irrelevant, but vaccine developers and others say it saves human lives — and the pandemic is their latest example, niranjana rajalakshmi • february 11, 2022.

Confining monkeys in small cages instead of their natural forest environment changes the results of experiments, some researchers say. [Credit: Wikimedia Commons]

Chimpanzee justice, roni jacobson • november 19, 2012, the monkey in the mirror, mary beth griggs • january 19, 2011, the end of biomedical research on u.s. chimps may imperil their wild brethren, mark d. kaufman • february 17, 2017.

In 2015 , the National Institutes of Health banned experiments on chimps, our closest genetic relatives . But that hasn’t ended tests on other primates, despite never-ending criticism from both ethicists and some researchers. 

This is the kind of research that Pfizer and Moderna relied on to get their COVID-19 vaccines to the market as soon as possible. Tests on rhesus macaques were important in speeding along the process, says Matthew R. Bailey , president of the Foundation For Biomedical Research . “To argue that primate research should not be conducted is itself unethical. It means you’ve delivered a death sentence to a lot of people who are depending on that research to save their lives,” he says.

But other animal experts, including several who formerly worked in research facilities, think it’s time to consider an outright ban on all monkey experiments. Noting that experimenting on chimps and other large apes is already banned in most countries , including the U.S., they argue that the monkeys in medical experiments suffer physically and psychologically. That raises not only ethical concerns but also scientific ones, since research monkeys living in a lab are more restricted in their movement than are monkeys that are free to roam.

In justifying the phase-out of chimp testing, NIH Director Dr. Frances Collins stated that “ new scientific methods and technologies have rendered their use in research largely unnecessary.” However, Collins has also said that continued testing on monkeys and other primates is vital to improving human health – even though chimps are actually much closer to humans than monkeys. We share almost 99% of our DNA with chimpanzees, compared to just 93% with rhesus monkeys . 

“It’s deeply illogical,” asserts Lisa Jones-Engel , a former primate scientist at the University of Washington who is now a consultant to People for the Ethical Treatment of Animals (PETA). “It’s just about money. Monkeys are smaller and cheaper than chimpanzees. There are more of them available in the wild. It has nothing to do with scientific or ethical relevance.”

The cost associated with buying and maintaining chimps was one of the factors that influenced the NIH to ban chimpanzee testing, according to Dr. Larry Carbone , a former university veterinarian in San Francisco who is now an independent animal welfare consultant. “Chimps will cost you $100,000, and you spend $100 a day to house them”, he says. On the other hand, a rhesus monkey costs about $7,000, and just $15 to $20 per day to house and feed, Carbone adds. 

Ultimately, the NIH concluded that “chimps are not useful enough” to justify the expense and the regulatory complications, since chimps are also an endangered species, unlike rhesus macaques, Carbone says.

No one knows exactly how many monkeys are used in research projects in the U.S. because the private companies that do much of the testing don’t have to disclose that information, according to Carbone. However, a 2019 federal report  puts the total at more than 68,000. Even so, there was a monkey shortage when the COVID vaccine research was at its peak — one that still continues. “The shortfall of monkeys began in 2018 and their overall demand increased when the pandemic struck”, says Sheri Hild , an NIH program director for primate research. 

The strongest case for continuing to use monkeys in experiments is for research on diseases like HIV and Ebola : diseases that monkeys are known carriers for . “The immune systems between humans and monkeys are so similar. That allows the testing of new treatment interventions,” says Caroline Pereira Bittencourt Passaes , who studies HIV-induced inflammation in rhesus macaques at the Pasteur Institute in Paris. “Giving HIV vaccines directly to humans would be a disaster,” she says. 

But even in HIV research, monkeys are not an ideal experimental model for humans. For one thing, they tend to get less severe HIV infections than humans, making it more difficult to design appropriate drugs and vaccines.  

Opponents of monkey testing, like Jones-Engels, extend this argument, claiming that “95% of drugs and treatments that work in animals, including monkeys, actually fail in humans.”. However, the NIH says the 95% failure rate applies to the entire drug discovery process, not to the animal tests that occur just before the human clinical trials. 

COVID-19 vaccines are the latest reason most biomedical researchers continue to defend monkey experimentation. In a recent statement , a network of seven primate research centers argued that monkey tests were essential for getting fast approval for the Pfizer and Moderna mRNA vaccines, as did a group of European researchers . Both companies tested their vaccines in monkeys and found they could induce SARS-CoV-2 antibodies. 

Monkey testing was important in the development of the COVID treatments and vaccines because the SARS-CoV-2 cellular receptor in humans is more similar to the one in monkeys than in other lab animals such as mice, according to the Pasteur Institute’s Passaes. “Monkeys have given a very valuable contribution to all these preclinical studies of drugs, monoclonal antibodies and of course, vaccines to fight COVID pandemic.”

But there was a dark side to some of that COVID-19 research, according to Jones-Engel. She says some monkeys used in the research were captured in forests in India and Bangladesh instead of being bred in captivity. “That is completely antithetical to best practices in the scientific community,” she says. “These monkeys were not bred for experiments. They were not specific-pathogen-free. How do you expect the results to be accurate?” For India’s COVAXIN  vaccine, for example, authorities allowed researchers to capture 30 rhesus monkeys from the wild. 

Primatologists point out that monkeys in cages are very different from their wild cousins, which inevitably affects experimental outcomes. “Some primates can walk for 50 kilometers a day, and they cannot do that in any lab. That’s a very big limitation,” says Constança Carvalho , a biologist at the University of Lisbon. 

Wild monkeys not only range widely, they also engage in a variety of mind-stimulating behaviors, everything from gouging holes in tree trunks and cracking open nuts to being curious like humans . Restricting their movement and suppressing their natural instincts in the lab setting makes some scientists doubt the accuracy of research conducted on them.

“Housing animals with large brains in cramped cages has a powerful effect on their physiological and neurological systems”, says John P. Gluck , a retired primatologist at the University of New Mexico who now works on animal welfare issues. “Practically, primate models are not as good as we once thought and that has a lot to do with how we house them.” This could be relevant for vaccine studies, since at least one study has shown that separating young monkeys from their families and housing them indoors affects their immune system .

If monkeys are used at all for research, Carvalho thinks that they should be treated the same way as humans. “You need to have someone appointed to be in charge of defending the best interests of that particular animal, in the same way you have someone responsible for a child. And this is not what is done in labs.”

Operators of primate research labs, however, say critics are misrepresenting conditions at some facilities. At the California Primate Research Center , for example, most monkeys are housed outdoors with their families, says  Kent Pinkerton , who is a scientist there. Outdoor monkeys “are happy with each other,” he adds, “and it’s not just one monkey with its offspring — it’s a colony.”

Opponents of monkey research cite the rise of alternative ways to model how humans may respond to experimental drugs, including  3D-printed human tissues and organoids and even organs on chips . Most of those tools, however, are still being developed and are not ready for widespread use yet.

And even when they are ready for prime time, alternative techniques like organs on chips can only be complementary tools to animal models, according to Hild, the NIH program director for primate research. “They definitely cannot be viewed as replacements for a whole organism,” she says. “They are just refinements that help in reducing animal usage in research.”

Even critics like Gluck acknowledge that ending primate testing overnight would slow down drug development — for the simple reason that the use of animals is such an ingrained tradition in biomedical research. “If all the primate research centers were emptied in the middle of a pandemic like this, it would have slowed down vaccine development, because that’s the way we think,” Gluck says, “even if it’s inferior thinking.”

About the Author

Niranjana Rajalakshmi

Niranjana Rajalakshmi is a veterinarian from South India. After a master’s in veterinary microbiology, she has combined her subject matter expertise with her fervor for storytelling and transitioned as a science journalist. From the three seasons of her city – summer, summerer, and summerest – she thinks moving to NYC will add at least one more season to her life and more flavor to her writing. Niranjana enjoys cooking, singing, and feeling nostalgic about her furry patients.

Experimenting on other species is fundamentally flawed because while they are like humans in their ability to feel pain and suffer, their physiology differs significantly from humans’. That’s why drugs that have passed animal tests with flying colors have sickened and even killed humans. Testing drugs on animals is as unnecessary as it is cruel. A prime example is the development of COVID vaccines. To expedite the process, the FDA and NIH allowed potential COVID vaccines to go to human clinical trials without first being tested extensively on animals. If they had required the usual years of animal tests, we still might not have an effective vaccine available.

YES YES YES! There are kinder and more accurate research methods available that take advantage of cutting-edge technology instead of cutting into animals.

It’s good to see this being written about, but the article needed some additional vetting. For instance: “But even in HIV research, monkeys are not an ideal experimental model for humans. For one thing, they tend to get less severe HIV infections than humans, making it more difficult to design appropriate drugs and vaccines.”

Monkeys are immune to HIV. Monkeys used in HIV research are infected with a different retrovirus called SIV (Simian Immunodeficiency Virus.) So, a different species being infected with a different virus is claimed to be HIV research.

I think that it is barbaric to experiment on any animals. How could any human experiment on any animal knowing the pain and suffering is going to be inflicted on that animal. This is something that needs to stop.

Yes let’s let’s end this!!!! Please! Hard to see these monkey suffering!

Yes shut down these labs. How can a human being do this. It’s barbaric. A person that does this has no soul or feelings.

A big thank you to the author of this article. How can we respect or believe the medical researchers for being so cruel to animals!! I agree their motivation is purely money and trying to win a prize. Leave the animals to live their lives free of human cruelty. People fighting for animal rights deserve a huge prize.

I wish someone would let people know that the monkey videos are staged and the monkeys were abused and most are dead, Kaka and Deim ones, multi pages fooling people thinking they are good people and treat Kaka like family, someone please make an article about what happen.

Leave a Reply

Your email address will not be published. Required fields are marked *

The Scienceline Newsletter

Sign up for regular updates.

February 08, 2023 Media Release More Than 380 Scientists Call for an End to Funding of Cruel Monkey Experiments at Harvard Medical School

For immediate release, 8 February 2023

Today, Harvard Law School’s Animal Law & Policy Clinic and the Wild Minds Lab at the University of St. Andrews School of Psychology and Neuroscience in the UK sent a letter to the National Institutes of Health (NIH) urging it to review and terminate its ongoing funding of cruel experiments on non-human primates at Harvard Medical School and elsewhere. More than 380 scientists, doctors, and academics from around the world joined the request to NIH—including renowned primatologists Dr. Jane Goodall, Dr. Ian Redmond, and Harvard’s Dr. Richard Wrangham .

As detailed in the letter, an NIH-funded Harvard Medical School lab run by neurobiologist Dr. Margaret S. Livingstone has used infant macaque monkeys to study visual recognition by depriving them of the ability to see faces, either by sewing their eyes shut or by requiring staff to wear welders’ masks around them. In some cases, the lab implants electrode arrays into the monkeys’ brains.

By design, these experiments require maternal deprivation—a fact that drew the ire of scientists last fall, when Proceedings of the National Academy of Sciences (PNAS) published an Inaugural Article by Dr. Livingstone entitled Triggers for Mother Love . The article describes the lab’s practice of taking infant macaques from their mothers shortly after birth and attempting to appease the mothers’ distress by giving them plush toys as “surrogate infants.”

“As a primatologist with decades of experience in the field, I can say with complete confidence that we know that infant primates and their mothers suffer greatly when they are separated,” said Dr. Wrangham, Moore Research Professor of Biological Anthropology at Harvard University.

He added: “We also know that depriving infants of the ability to see faces will have adverse impacts on their brain and eye development. Taking infant monkeys from their mothers to use in invasive brain experiments could only be justified by expectations of extraordinarily important benefits for the monkeys themselves, or for humans. Because that high ethical bar has not been met, I see no legitimate need for any such research.”

Dr. Livingstone has received over $32 million in NIH grants since the 1980s.

“These studies fail on both scientific and ethical grounds,” said Dr. Catherine Hobaiter, Principal Investigator at the Wild Minds Lab. “The doublethink argument that maternally-separated individuals represent appropriate models for conditions such as anxiety, while arguing these methods do not cause significant distress is fundamentally flawed. Our fundamental role as scientists is to update, refine, and redefine our understanding of the world around us. Doing so must include not only our theoretical positions, but our ethical responsibility to the animals we have given no choice in becoming our subjects of study.”

Last fall, the Wild Minds Lab submitted a letter on behalf of 260 animal behavior scientists calling for PNAS to retract Triggers for Mother Love because it promotes cruel practices long known to cause monkeys lasting behavioral and psychological harms. The journal declined to publish the letter. The Harvard Animal Law & Policy Clinic also called on Harvard Medical School’s Institutional Animal Care and Use Committee (IACUC) to review Dr. Livingstone’s research protocols with the aim of ending cruel experiments. The IACUC has not responded.

“As long as non-human primates are used in scientific experiments, we are morally obligated to provide them with sufficient social conditions that ensure their emotional wellbeing,” said Gal Badihi, a graduate research student in the Wild Minds Lab. “This is not only an ethical requirement but essential for research validity and integrity.”

Today’s request to the NIH places Dr. Livingstone’s research in a broader context and calls for the agency to “to internally review not only these particular studies at the Harvard Medical School, but also all other ongoing non-human primate experiments of a similar nature, and to permanently end funding for current or future projects that lack ecological validity and involve cruel and inhumane treatment of animals used in experimentation.” The signatories further urge the NIH to direct some of its considerable funding for research to develop alternatives to animal testing.

“An institution like Harvard Medical School should be at the forefront of developing alternatives to animal research,” said Rebecca Garverman, Clinical Fellow in Harvard’s Animal Law & Policy Clinic. “The NIH must lead the way by terminating funding of cruel experiments on monkeys and instead backing innovative, human-relevant approaches.”

For more information or interview requests, please contact:

Sarah Pickering, Harvard Animal Law & Policy Clinic, [email protected] , + 1 617-852-6484

Gal Badihi. Wild Minds Lab, [email protected]

Catherine Hobaiter, Wild Minds Lab, [email protected]

• Future Perfect

What can caged lab monkeys tell us about free human beings?

Where biomedicine gets it wrong about primate research.

by Garet Lahvis

A friend says they can always tell when you’re hungover. The way you close the cage latch. With so little to do, their attention can focus on those subtle differences in movement: the way it turns, whether it drops all or part of the way.

After easing the latch back open, the monkey climbs down to the concrete floor, past the rolling service station with its cotton swabs, boxes, bottles, and syringes.

Out in the hallway, two caretakers see him crouched against the cinderblock wall, hands pressed against the cream-colored paint, shoulders pulled up, head turned sideways and facing down the corridor, eyes toward them.

Over the past couple of years, experimentation on non-human primates has had a run of bad publicity. In 2020, media attention focused on a federal laboratory that studied the neurobiology of anxiety by scaring monkeys with toy snakes . In November, the US Justice Department indicted members of an alleged “primate smuggling ring” for trafficking and selling wild long-tailed macaques , an endangered species, to biomedical researchers in the US.

Around the same time, attention turned to the Livingstone Lab at Harvard University, where researchers sewed baby macaques’ eyelids shut to investigate how visual deprivation affects brain development. The controversy landed in Science magazine , where scientists debated the ethics of blinding monkeys. I was asked to weigh in. But my questions were different — less about the blinded macaques, and more about the controls staring at their cage walls.

For 16 years, I worked as a professor for medical schools in Wisconsin and Oregon. Both universities had primate centers. I knew about their operations, though I never experimented on primates. Instead, my laboratories mostly studied mice. Our goal was to identify the genetic and pollutant risk factors for autism, a disability that features challenges with social emotions. We never successfully identified any risk factors, but we did discover that mice enjoy one another’s company and have empathy for their pain.

After publishing more than 40 scientific papers, I left academia. In part, I left on principle. I believed that if we experimented on animals, we were obligated not to waste them. I also believed that biomedical scientists were obliged to consider the implications of our own discoveries — like how our animals were responding to their cage environments — so we could do better science. Eventually, I lost faith in the process. I also lost the stomach to confine sentient creatures to tiny cages.

Scientists know that the tight confinement of standard laboratory cages distorts the psychology and physiology of our animal subjects. Yet despite a half-century of evidence, we continue to cage them as if their biology is baked into their genetics. From decades of rodent studies, scientists know that an animal’s brain anatomy and physiology are highly vulnerable to even modest changes in their living environments. Mice housed in standard cages, rather than slightly larger ones furnished with blocks and tunnels for mental stimulation, are more susceptible to drug abuse, genetic modifications, and toxic chemicals. Monkeys, nearly our next of kin, can become so mentally deranged by their cage environments that they no longer resemble healthy humans. They might have more in common with children housed in Romanian orphanages in the 1980s and 1990s, who were so deprived of human contact that they still struggle with lifelong physiological and psychological disabilities .

Can we use mentally damaged animals to model mental health?

Primate experiments have undeniably aided the discovery of treatments for human disease, particularly vaccines and surgical techniques. More than a century ago, for example, scientists collected extracts from the spinal cord of a boy who died of polio, injected them into monkeys, studied how the infection spread, and then developed a vaccine that nearly eradicated polio. Much more recently, primate experiments were useful for developing a brain-spine interface that can restore the ability of people with paralysis to walk .

But these successes have been rare. Part of the problem lies in the question we now ask. Globally, scientists use approximately 100,000 non-human primates at any given time, often to explore highly nuanced questions, like finding risk factors and treatments for mental health challenges — autism, ADHD, schizophrenia, addiction, anxiety, depression, post-traumatic stress disorder. And here, we mostly fail. Most drugs showing extreme promise in animal studies fall short in human trials. We haven’t developed a new category of drugs for treating psychiatric illness in more than 50 years; new psychiatric drugs introduced over the same period have been modified versions of existing drugs.

Scientists also use primates to understand how human-like immune systems respond to infectious diseases — but, like mental health, immunity is also highly sensitive to how the monkeys feel inside their cages.

Housing for monkeys is tight. The standard cage for a rhesus macaque, a common laboratory primate, is about 2.5 feet across, narrow enough for its inhabitant to touch both walls at once. By contrast, their wild relatives can navigate home ranges averaging about 1.5 square miles. Macaques are built to navigate 740 American football fields’ worth of savannah grasslands and forest canopies. Yet inside biomedical labs, they typically get confined to the equivalent of a telephone booth .

Housing situations vary. Some live “singly housed” — a situation that resembles solitary confinement, often for a few months, sometimes for life. Others get “protected contact” — two monkeys separated by a grate that permits fingertips to touch. Others live as “buddies in a cage” — sharing the space of a shower stall until one buddy gets pulled out, often leaving the remaining one stressed and with a depressed immune system for weeks to months depending on his temperament (and, perhaps, how close he felt to his buddy).

In some respects, singly housed monkeys have it better than human inmates in solitary. For instance, they can more easily hear each other vocalize. Some have handheld mirrors to see their neighbors. Many have opportunities to rattle their squeeze bars, the metal poles fixed to the cage’s back walls, used to pull the monkeys forward for procedures like injections and blood draws. But while the United Nations considers more than 15 days of solitary confinement in humans to be torture, research monkeys often get a lifetime — especially if they lose it and assault their buddy in the cage. And although humans in solitary get time each day outside their cell, primates usually don’t get a break.

Studies show that human solitary confinement in prisons can cause depression, anxiety, paranoia, violent fantasies, full-blown panic attacks, hallucinations, psychosis, and schizophrenia. Some incarcerated people also self-mutilate, cutting their wrists and arms, ingesting foreign objects, self-burning, and reopening stitches from prior injuries. Physical symptoms include cardiovascular disease , migraine headaches, back pain, profound fatigue, and deterioration of eyesight.

Likewise, lab monkeys express behaviors that suggest psychological trauma. Among 362 singly housed rhesus monkeys, a study found that 89 percent expressed abnormal behavior. Most were what we call “stereotypies” — repetitive behaviors that serve no purpose, save coping. Some monkeys pace in circles. Others rock or bounce for hours, like idling engines. Some methodically somersault. Others incessantly rattle their squeeze bars. A few spend time in “eye salute,” a euphemism for self-stimulation by sticking fingers into one’s own eye.

My friend tells me he’s seen some monkeys cross the line of no return. Unresponsive to the caretakers interacting with them, they can’t stop rocking, twirling, circling, or twitching. They can’t pull away from the back of the cage. Their eyes no longer make contact.

Up to 15 percent of laboratory monkeys self-mutilate . They might pluck single hairs from their backsides until they turn bright pink, or bang their heads repeatedly against their cage walls, or bite themselves deep enough to require sutures. Unlike their wild brethren, caged macaques often paint the walls with their feces — a substance they can manipulate.

Nearly one-quarter of caged macaques express “floating limb” behaviors. Watch one for long enough and you might see his leg writhe or kick. He might grab his leg as it slowly elevates, seemingly out of control. It might hover behind his back. Or his foot might relentlessly smack the back of his head. He might respond by attacking his leg, as if it were foreign.

Scientists have normalized the idea that their caged primates are healthy

I suspect these behaviors are manifestations of an intolerable allostatic load : a “wear and tear on the body and brain resulting from chronic overactivity or inactivity of physiological systems that are normally involved in adaptation to environmental challenge.” Cramped living spaces deny primates the ability to act on their innate motivations: to seek pleasures, avoid discomforts, and explore complex and changing environments. Oysters don’t need these motivations because they can flourish cemented to a rock. For moving animals, motivations help us make decisions. An innate taste for sugar and salt prompts us to seek the calories and sodium we need to survive. When scientists remove the pleasure center of a rat brain, called the nucleus accumbens, they no longer eat .

Curiosity is also an innate drive. In the wild, animals feel compelled to investigate their environments — where to go, what to eat, with whom to interact — to know their options when their situations change. Scientists leverage an animal’s innate curiosity to study how memory works: Introduce a laboratory mouse to a novel object and a familiar one, and if the rodent remembers the object they encountered before, they’ll spend more time sniffing the unfamiliar one. Since the 1950s , scientists have known that monkeys will solve complex puzzles simply for the challenge of solving the task.

I suspect that, deprived of varied and ongoing challenges to overcome, environments to explore, or a natural range of body movements, caged monkeys — studied because they resemble us — go insane with boredom. Still, I’ve heard scientists insist that these animals are happier in cages because they get food, water, and safety from predators. They’ll tell you laboratory primates get “environmental enrichment,” like a rubber ball stuffed with a treat, a toy dangling from a cage door, a mirror to play with, or snacks scattered on the cage floor. I suppose they get exercise, too. For glutes and biceps, they can rock back and forth or rattle their cage doors. For a cardio workout, they can pace in circles or slam themselves against the cage walls.

Here’s the rub. Scientists must believe that lab animals thrive physically and mentally — not for animal welfare reasons, but to justify our experiments. We need healthy controls, not psychologically broken ones, to benchmark our disease models. And we need the animals used as disease models to be otherwise healthy because we lack the scientific capacity to separate the biology of a nuanced disorder, like autism or ADHD, from confounding factors like the mental damage caused by incarceration.

My qualm with the Livingstone Lab’s experiment, the one that entailed sewing baby monkeys’ eyelids shut, is not primarily ethical but scientific. They claimed that by blinding monkeys, they could gain “insight into evolutionary changes in the functional organization of high-level visual cortex.” But they wrongly presumed that their “healthy” control monkeys, who were denied most visual stimulation save the depleted sensory environment of a steel-gray cage, had normal visual functioning.

By describing what they’re studying as “evolutionary changes,” the researchers lured us into believing the ridiculous — that brain development behind steel bars is not only normal but natural enough to be relevant to evolutionary changes occurring outside the lab. Yet their monkeys experienced no full spectrum of color, no natural movement like the rustling of leaves, and no passing landscape. Like most other primate experimenters, the lab normalized the idea that monkeys naturally live inside telephone booths, not in the vast, dynamic, and aesthetically complex expanses of nature.

What bothers me most is that the scientific community expresses so little concern about whether we’re chasing artifacts of confinement. And for the few of us who ask, the answer is loud with silence.

Can we do better?

Admittedly, scientists are in a fix. Our problem might have begun during the late Middle Ages, about 800 years ago, when Italian philosopher and theologian Thomas Aquinas argued that because animals lacked “rational souls,” they were like machines. Centuries later, René Descartes, a father of modern science, called animals automata , robots driven by reflexes, without thoughts or feelings — like the mechanical men of his era, built to hammer the bells of village clock towers. Armed with this philosophy, scientists tacked dogs to walls and opened them up without anesthesia to learn that the heart, not the liver, pumped blood. Their shrieks and howls were thought of as if they were bells ringing on the hour.

The cruel irony is that the ethical justification for experimenting on animals — that they lack subjective experiences — allowed us to find cogent evidence that they do. Now we’re forced to ignore what we’ve learned from science — so that we can keep doing it.

Rather than envision a new paradigm, scientists have devised arguments to keep things the same, claiming, for example, that we need small cages to control for confounding variables in an animal’s environment. But we routinely accept the inescapable variables inside their confines — sound, lighting, food quality, social situations — that are either impossible or too inconvenient to control. In truth, we use small cages because they afford the cheapest and most convenient way to generate scientific publications.

What could scientists do differently? We could pivot to more helpful alternatives. We could deploy spatially and temporally complex spaces to study smaller organisms under conditions where they might thrive like the free human beings they are meant to resemble. Mice and rats could live in small research barns with varied food and shelter options and penned-in outdoor access, where they could author their own experiences and meet ongoing and unpredictable challenges . Zebrafish, snails, and fruit flies could also get environments complex enough to operate as they might in the wild. Remote technologies could help deliver various drugs and biomolecules to moving animals and help us monitor their responses.

Biomedical research institutions could double down on financially neglected health research programs, like disease prevention. We could expand monitoring of human and wildlife populations for elevated pockets of disease — like cancer, congenital disorders, and mental illness — arising from our exposures to thousands of pesticides and industrial contaminants.

Present-day concerns over “forever chemicals” in our food and drinking water , and the enormous price tag we now face for cleanup, could have been predicted and more easily remediated decades ago, when epidemiologists and chemists found evidence of their presence in humans and wildlife. The elevated prevalence of congenital disorders, endocrine disruption, immune dysfunction, and mental illness found in fish-eating wildlife in pollutant hot spots around the Great Lakes and along the US coasts could be used to identify regional exposures to chemical mixtures that also threaten human health. Why not focus on these issues ? With advanced epidemiological computer modeling, and gene sequencing tools, along with high-efficiency cell culture systems that can test multiple chemicals at a time without the use of animals, we could identify harmful compounds, then remove them. The potential is far greater than whatever we might learn from using rubber snakes to scare mentally enfeebled monkeys.

Many people believe that science differs from blind faith. If that’s true, I wonder how many more rabbit holes we’ll plumb before we see that cage-deteriorated primates don’t resemble free human beings. Perhaps scientists collectively disregard animal subjectivity out of fear of the moral implications of experimenting on other sentient creatures. Or are we blinded by our ambitions for careers and legacies? No matter the cause, we have obligations to the societal trust placed in us. And if we’re 1,000 years overdue for a paradigm shift, let’s hope that today’s young scientists can find the unfettered clarity of sight to make it happen.

The fugitive still cowers in the main hall, cheek and chest pressed against the cinderblock, eyes looking upward, seemingly fixed on the audible ballast of the fluorescent lights. Or the fly circling, then resting, beneath it. He might hear the buzz of both, one against the other, a two-tone that cannot calm the anxiety of being outside that room. Having known only metal walls and the fetid mire of idling bodies, he lacks familiarity with concrete surfaces, unfouled air, and the taking of risks.

The protocol is straightforward. Face the escapee, chest out, shoulders straight, eyes toward his. Wedge open the colony room door. Use push brooms to coax him back into his cage.

The convict returns. They close his cage door. He pivots, then grabs the bars of the door as if he’s now the master, then shakes them violently like he’s trying to get out. He’ll be studied over and over again because he somehow represents us. Maybe he does.

Garet Lahvis was an associate professor and the graduate program director of behavioral neuroscience at Oregon Health and Science University. He is currently writing a book for the University of Chicago Press on his experiences with the limits of science, and of the scientific community, in addressing some of our most pressing biomedical issues. Follow him on X (formerly Twitter) at @GLahvis .

• Animal Welfare
• Neuroscience

Most Popular

• Kamala Harris’s speech triggered a vintage Trump meltdown
• A Trump judge ruled there’s a Second Amendment right to own machine guns
• The difference between American and UK Love Is Blind
• The massive Social Security number breach is actually a good thing
• What you need to know about the new Covid-19 vaccine

Today, Explained

Understand the world with a daily explainer plus the most compelling stories of the day.

This is the title for the native ad

More in Future Perfect

Scientific fraud kills people. Should it be illegal?

Organ companies are getting up to pancreas hijinks.

Even OpenAI warns that chatting with an AI voice can breed “emotional reliance.”

However current companies do financially, the big AI safety challenges remain.

But there might be global consequences.

Researchers wildly underestimated how many people don’t have safe drinking water.

An official website of the United States government

Here's how you know

Official websites use .gov A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS A lock ( Lock A locked padlock ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

• The Attorney General
• Organizational Chart
• Budget & Performance
• Privacy Program
• Press Releases
• Photo Galleries
• Guidance Documents
• Publications
• Information for Victims in Large Cases
• Justice Manual
• Business and Contracts
• Why Justice ?
• DOJ Vacancies
• Legal Careers at DOJ
• Our Offices

Archived Press Releases

Archived News

Para Notícias en Español

Iowa Man Charged with Distributing Videos Depicting Monkey Torture and Mutilation

An indictment was unsealed today in which an individual was charged based on his involvement with online groups dedicated to creating and distributing videos depicting acts of extreme violence and sexual abuse against monkeys.

Philip Colt Moss, of Iowa, was charged with conspiracy to create and distribute so-called “animal crush videos,” and with distributing animal crush videos. According to court documents, in March and April 2023, Moss allegedly conspired with Nicholas Dryden and Giancarlo Morelli to create and distribute videos depicting acts of sadistic violence against baby, adolescent and adult monkeys. Dryden and Morelli were previously indicted and are awaiting trial. 

The videos alleged to have been created as part of the conspiracy included depictions of monkeys having their genitals burned, having their genitals cut with scissors, being sodomized with a wooden skewer and being sodomized with a spoon.

If convicted, Moss faces a maximum penalty of five years in prison for the conspiracy charge and a maximum penalty of seven years in prison for the charges related to the creation and distribution of animal crush videos. A federal district court judge will determine any sentence after considering the U.S. Sentencing Guidelines and other statutory factors.

Assistant Attorney General Todd Kim of the Justice Department’s Environment and Natural Resources Division and U.S. Attorney Kenneth L. Parker for the Southern District of Ohio made the announcement.

The U.S. Fish and Wildlife Service and FBI investigated the case.

Senior Trial Attorney Adam Cullman of the Environment and Natural Resources Division’s Environmental Crimes Section and Assistant U.S. Attorney Tim Oakley for the Southern District of Ohio are prosecuting the case.

An indictment is merely an allegation. All defendants are presumed innocent until proven guilty beyond a reasonable doubt in a court of law.

Related Content

Two individuals were charged for their involvement with online groups dedicated to creating and distributing videos depicting acts of extreme violence and sexual abuse against monkeys.

A federal grand jury charged a New York man in a three-count indictment alleging he illegally shipped eastern box turtles and three-toed box turtles, both protected wildlife species, from the...

Envigo RMS LLC pleaded guilty today to conspiring to knowingly violate the Animal Welfare Act, and Envigo Global Services Inc. pleaded guilty to a felony of conspiring to knowingly violate...

• Alzheimer's disease & dementia
• Arthritis & Rheumatism
• Attention deficit disorders
• Autism spectrum disorders
• Biomedical technology
• Diseases, Conditions, Syndromes
• Endocrinology & Metabolism
• Gastroenterology
• Gerontology & Geriatrics
• Health informatics
• Inflammatory disorders
• Medical economics
• Medical research
• Medications
• Neuroscience
• Obstetrics & gynaecology
• Oncology & Cancer
• Ophthalmology
• Overweight & Obesity
• Parkinson's & Movement disorders
• Psychology & Psychiatry
• Radiology & Imaging
• Sleep disorders
• Sports medicine & Kinesiology
• Vaccination
• Breast cancer
• Cardiovascular disease
• Chronic obstructive pulmonary disease
• Colon cancer
• Coronary artery disease
• Heart attack
• Heart disease
• High blood pressure
• Kidney disease
• Lung cancer
• Multiple sclerosis
• Myocardial infarction
• Ovarian cancer
• Post traumatic stress disorder
• Rheumatoid arthritis
• Schizophrenia
• Skin cancer
• Type 2 diabetes
• Full List »

share this!

August 23, 2024

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

Smallpox vaccination in childhood could offer protection against monkeypox clade II viruses, study finds

by European Centre for Disease Prevention and Control (ECDC)

A study by co-authors from the ECDC, WHO and national public health institutes in four European countries, and published in Eurosurveillance, has found that prior smallpox vaccination in childhood could protect against infections caused by monkeypox virus (MPXV) clade II in men. However, the estimated degree of protection varied among countries, highlighting the need for further research to validate the study findings.

In light of the 2022–2023 outbreak of mpox in Europe that mainly affected certain groups with high-risk behavior among men who have sex with men, the study sought to determine the effectiveness of historical smallpox vaccination during childhood against laboratory-confirmed mpox, to inform vaccination efforts.

Case-based surveillance data were selected from countries that collected information on prior smallpox vaccination status of mpox cases and had available data on historical smallpox vaccination coverage, namely Denmark, France (mainland only), the Netherlands (mainland only) and Spain.

The study analyzed mpox cases born in these countries during the height of national smallpox vaccination campaigns (latest in 1971). Too few mpox cases in females were reported to adjust for sex in the analysis, so only cases recorded as male were included.

Vaccine effectiveness and corresponding 95% confidence intervals (CI) for each country were then estimated using logistic regression as per the Farrington screening method. A pooled estimate was then calculated using a random effects model.

Results and public health implications

Estimated historical smallpox coverage was high (80–90%) across all countries until the end of the 1960s, dropping off considerably during the last 10 years of vaccination programs.

Estimates of vaccine effectiveness of prior smallpox vaccination against mpox caused by MPXV clade II varied widely between countries, ranging from 42% in the Netherlands to 84% in Spain, possibly reflecting different booster strategies. The pooled vaccine effectiveness estimate was 70% with a wide 95% confidence interval of 23–89%, indicating a high level of uncertainty.

The study findings suggest that historical childhood smallpox vaccination in a European setting could protect two-thirds of men against mpox caused by MPXV clade II. However, there was significant uncertainty in the results and variation between countries. The results of this study are therefore not sufficient to support differential smallpox vaccination to protect against mpox based on historical smallpox vaccination status or age.

The authors recommend that individuals with a high risk of exposure be offered mpox vaccination, regardless of vaccination history. With the recent surge of clade Ib mpox cases in several countries in central and East Africa, there is an urgent need to conduct similar studies on the effectiveness of the smallpox vaccine against the most recent circulating clade.

Explore further

Feedback to editors

Study identifies metabolic switch essential for generation of memory T cells and anti-tumor immunity

Aug 24, 2024

Multiple sclerosis appears to protect against Alzheimer's disease

Aug 23, 2024

Good sleep habits important for overweight adults, study suggests

Mediterranean diet supplement can affect epigenetics associated with healthy aging

New method for quantifying boredom in the body during temporary stress

Cancer researchers develop new method that uses internal clock inside tumor cells to optimize therapies

Strength training activates cellular waste disposal, interdisciplinary research reveals

Being a 'weekend warrior' could be as good for brain health as exercising throughout the week

Simple blood test for Alzheimer's disease could change how the disease is detected and diagnosed

Chlamydia can settle in the intestine, organoid experiments reveal

Related stories.

Historical smallpox vaccination may confer some protection against mpox disease

Jul 19, 2024

Mpox 'not the new Covid', says WHO

Aug 20, 2024

Mpox vaccine maker says 'better prepared' than in 2022

Aug 22, 2024

Report investigates willingness to receive smallpox vaccine for mpox prevention in Japan

Jul 27, 2023

Mpox vaccine maker gets European order for 440,000 doses

Is there a vaccine for mpox? Who can get the shot and where? How to find it in Florida

Aug 21, 2024

Recommended for you

Spike mutations that help SARS-CoV-2 infect the brain discovered

Men infected with high-risk types of HPV could struggle with fertility

Macrophage mix helps determine rate and fate of fatty liver disease, study finds

A new culprit in Huntington's: Brain organoid model implicates gene in disease progression

Universal flu vaccine candidate protects against infection in mice

Let us know if there is a problem with our content.

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form . For general feedback, use the public comments section below (please adhere to guidelines ).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

E-mail the story

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Medical Xpress in any form.

Newsletter sign up

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

More information Privacy policy

Donate and enjoy an ad-free experience

We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account.

E-mail newsletter

• Site Search:
• Site Search
•  Help/Tutorials
•  Settings
•  Messages

Job Posting: Program Manager

Department of Justice

$7,643.00 - $9,496.00 per Month

Final Filing Date: 8/26/2024

Job Description and Duties

Are you looking for a great job where your contributions truly matter? Within the Justice Data Investigative Services Bureau, it is our mission to provide reliable data and investigative services to our criminal justice partners and public policy stakeholders to support their efforts in protecting Californians. Our values - believe in teamwork, operate with integrity, lead by example, dare to be innovative, represent our commitment to an inclusive and supportive work culture. Please consider joining our team!

Under the general direction of the Staff Services Manager (SSM) III, develop the Controlled Substance Utilization Review and Evaluation System (CURES) Program strategic plan for business operations; direct program activities to support ongoing improvements to the CURES web application and web services; direct program activities in support of interstate and intrastate access to CURES data; provide direct supervision to two SSM Is; direct program activity related to the CURES Help Desk Section and Program Services Section; represent the Department to external agencies, special interest groups, and the Legislature in meetings; direct program responses to bureau assignments; direct program administrative activities related to budgets, procurements, and personnel matters.

Please let us know how you heard about our position by taking this brief survey:

https://www.surveymonkey.com/r/P7X675V

You will find additional information about the job in the Duty Statement .

Working Conditions

This position is eligible for telework 5 days a week, in accordance with the Statewide Telework Policy, and will be required to report to the office as needed/required. A teleworker is considered Remote-centered if they work fifty percent or more of their time from an alternate work location. The successful candidate must reside in California upon appointment.

Minimum Requirements

• STAFF SERVICES MANAGER II (SUPERVISORY)

Additional Documents

• Job Application Package Checklist
• Duty Statement

Position Details

Department information.

This position is located in the California Justice Information Services Division, Justice Data and Investigative Services Bureau, Justice Data and Auditing Branch, Client Services and Controlled Substance Utilization Review & Evaluation System Program.

Please disregard the SROA/Surplus language below as the Department of Justice requires applicants to submit their SROA/Surplus Letter if that is the basis of their eligibility.

For more information about the department, please visit the Attorney General’s website at www.oag.ca.gov .

Special Requirements

A fingerprint check is required.

Clearly indicate JC-443622 in the “Examination(s) or Job Title(s) For Which You Are Applying” section of your State Application.

If you are using education to meet the minimum qualifications for this position, you must submit a copy of your transcript or diploma . An official transcript will be required prior to appointment.

A background check is required (if applicable).

Application Instructions

Completed applications and all required documents must be received or postmarked by the Final Filing Date in order to be considered. Dates printed on Mobile Bar Codes, such as the Quick Response (QR) Codes available at the USPS, are not considered Postmark dates for the purpose of determining timely filing of an application.

Who May Apply

How To Apply

Address for Mailing Application Packages

You may submit your application and any applicable or required documents to:

Address for Drop-Off Application Packages

You may drop off your application and any applicable or required documents at:

Required Application Package Documents

The following items are required to be submitted with your application. Applicants who do not submit the required items timely may not be considered for this job:

• Current version of the State Examination/Employment Application STD Form 678 (when not applying electronically), or the Electronic State Employment Application through your Applicant Account at www.CalCareers.ca.gov. All Experience and Education relating to the Minimum Qualifications listed on the Classification Specification should be included to demonstrate how you meet the Minimum Qualifications for the position.
• Resume is required and must be included.
• Statement of Qualifications - The Statement of Qualifications (SOQ) is required for this position. The SOQ is a narrative discussion of the candidate's education, training, experience, and skills as it relates to the desirable qualifications and duties for the position. The SOQ serves as documentation of each candidate's ability to present information clearly and concisely in writing. The SOQ should explain in detail why the candidate believes his or her knowledge, skills, and abilities could apply towards this position. Your response should be typed in Arial 12 point font and no more than two pages in length. Resumes will not be considered a substitute for the SOQ.

Desirable Qualifications

• Reason logically, creatively, and utilize a variety of analytical techniques to resolve complex governmental and managerial problems.
• Develop and evaluate alternatives.
• Analyze data and present ideas and information effectively both orally and in writing.
• Consult with and advise administrators or other interested parties on a wide variety of subject-matter areas.
• Gain and maintain the confidence and cooperation of those contacted during the course of work.
• Review and edit written reports, utilize interdisciplinary teams effectively.
• Manage a complex Staff Services program.
• Establish and maintain project priorities.
• Develop and effectively utilize all available resources.

Benefit Information - Please access this link for information on benefits afforded to employees who work for the State of California - https://www.calhr.ca.gov/Pages/California-State-Civil-Service-Employee-Benefits-Summary.aspx

Contact Information

The Human Resources Contact is available to answer questions regarding the position or application process.

Please direct requests for Reasonable Accommodations to the interview scheduler at the time the interview is being scheduled. You may direct any additional questions regarding Reasonable Accommodations or Equal Employment Opportunity for this position(s) to the Department's EEO Office.

Additional Information on Application Filing

Please note, if using the United States Postal Service for delivery, there is no guarantee that your application will be date stamped and will arrive by the final filing date. If your application does not have a postmark or date stamp and arrives after the final filing date, your application will not be accepted. Therefore, to ensure timely delivery of your application, it is recommended that you use either electronic delivery, parcel service, or certified mail. Using one of these options will provide proof of delivery prior to the final filing date.

Equal Opportunity Employer

The State of California is an equal opportunity employer to all, regardless of age, ancestry, color, disability (mental and physical), exercising the right to family care and medical leave, gender, gender expression, gender identity, genetic information, marital status, medical condition, military or veteran status, national origin, political affiliation, race, religious creed, sex (includes pregnancy, childbirth, breastfeeding and related medical conditions), and sexual orientation.

It is an objective of the State of California to achieve a drug-free work place. Any applicant for state employment will be expected to behave in accordance with this objective because the use of illegal drugs is inconsistent with the law of the State, the rules governing Civil Service, and the special trust placed in public servants.

Automatic log out in

Select 'Stay Logged In' below to resume your activity.

You must enable Javascript to use this site.