8612 stanford prison experiment

Stanford Prison Experiment: Zimbardo’s Famous Study

Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

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

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

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

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

On This Page:

• The experiment was conducted in 1971 by psychologist Philip Zimbardo to examine situational forces versus dispositions in human behavior.
• 24 young, healthy, psychologically normal men were randomly assigned to be “prisoners” or “guards” in a simulated prison environment.
• The experiment had to be terminated after only 6 days due to the extreme, pathological behavior emerging in both groups. The situational forces overwhelmed the dispositions of the participants.
• Pacifist young men assigned as guards began behaving sadistically, inflicting humiliation and suffering on the prisoners. Prisoners became blindly obedient and allowed themselves to be dehumanized.
• The principal investigator, Zimbardo, was also transformed into a rigid authority figure as the Prison Superintendent.
• The experiment demonstrated the power of situations to alter human behavior dramatically. Even good, normal people can do evil things when situational forces push them in that direction.

Zimbardo and his colleagues (1973) were interested in finding out whether the brutality reported among guards in American prisons was due to the sadistic personalities of the guards (i.e., dispositional) or had more to do with the prison environment (i.e., situational).

For example, prisoners and guards may have personalities that make conflict inevitable, with prisoners lacking respect for law and order and guards being domineering and aggressive.

Alternatively, prisoners and guards may behave in a hostile manner due to the rigid power structure of the social environment in prisons.

Zimbardo predicted the situation made people act the way they do rather than their disposition (personality).

To study people’s roles in prison situations, Zimbardo converted a basement of the Stanford University psychology building into a mock prison.

He advertised asking for volunteers to participate in a study of the psychological effects of prison life.

The 75 applicants who answered the ad were given diagnostic interviews and personality tests to eliminate candidates with psychological problems, medical disabilities, or a history of crime or drug abuse.

24 men judged to be the most physically & mentally stable, the most mature, & the least involved in antisocial behaviors were chosen to participate.

The participants did not know each other prior to the study and were paid $15 per day to take part in the experiment.

Participants were randomly assigned to either the role of prisoner or guard in a simulated prison environment. There were two reserves, and one dropped out, finally leaving ten prisoners and 11 guards.

Prisoners were treated like every other criminal, being arrested at their own homes, without warning, and taken to the local police station. They were fingerprinted, photographed and ‘booked.’

Then they were blindfolded and driven to the psychology department of Stanford University, where Zimbardo had had the basement set out as a prison, with barred doors and windows, bare walls and small cells. Here the deindividuation process began.

When the prisoners arrived at the prison they were stripped naked, deloused, had all their personal possessions removed and locked away, and were given prison clothes and bedding. They were issued a uniform, and referred to by their number only.

The use of ID numbers was a way to make prisoners feel anonymous. Each prisoner had to be called only by his ID number and could only refer to himself and the other prisoners by number.

Their clothes comprised a smock with their number written on it, but no underclothes. They also had a tight nylon cap to cover their hair, and a locked chain around one ankle.

All guards were dressed in identical uniforms of khaki, and they carried a whistle around their neck and a billy club borrowed from the police. Guards also wore special sunglasses, to make eye contact with prisoners impossible.

Three guards worked shifts of eight hours each (the other guards remained on call). Guards were instructed to do whatever they thought was necessary to maintain law and order in the prison and to command the respect of the prisoners. No physical violence was permitted.

Zimbardo observed the behavior of the prisoners and guards (as a researcher), and also acted as a prison warden.

Within a very short time both guards and prisoners were settling into their new roles, with the guards adopting theirs quickly and easily.

Asserting Authority

Within hours of beginning the experiment, some guards began to harass prisoners. At 2:30 A.M. prisoners were awakened from sleep by blasting whistles for the first of many “counts.”

The counts served as a way to familiarize the prisoners with their numbers. More importantly, they provided a regular occasion for the guards to exercise control over the prisoners.

The prisoners soon adopted prisoner-like behavior too. They talked about prison issues a great deal of the time. They ‘told tales’ on each other to the guards.

They started taking the prison rules very seriously, as though they were there for the prisoners’ benefit and infringement would spell disaster for all of them. Some even began siding with the guards against prisoners who did not obey the rules.

Physical Punishment

The prisoners were taunted with insults and petty orders, they were given pointless and boring tasks to accomplish, and they were generally dehumanized.

Push-ups were a common form of physical punishment imposed by the guards. One of the guards stepped on the prisoners” backs while they did push-ups, or made other prisoners sit on the backs of fellow prisoners doing their push-ups.

Asserting Independence

Because the first day passed without incident, the guards were surprised and totally unprepared for the rebellion which broke out on the morning of the second day.

During the second day of the experiment, the prisoners removed their stocking caps, ripped off their numbers, and barricaded themselves inside the cells by putting their beds against the door.

The guards called in reinforcements. The three guards who were waiting on stand-by duty came in and the night shift guards voluntarily remained on duty.

Putting Down the Rebellion

The guards retaliated by using a fire extinguisher which shot a stream of skin-chilling carbon dioxide, and they forced the prisoners away from the doors. Next, the guards broke into each cell, stripped the prisoners naked and took the beds out.

The ringleaders of the prisoner rebellion were placed into solitary confinement. After this, the guards generally began to harass and intimidate the prisoners.

Special Privileges

One of the three cells was designated as a “privilege cell.” The three prisoners least involved in the rebellion were given special privileges. The guards gave them back their uniforms and beds and allowed them to wash their hair and brush their teeth.

Privileged prisoners also got to eat special food in the presence of the other prisoners who had temporarily lost the privilege of eating. The effect was to break the solidarity among prisoners.

Consequences of the Rebellion

Over the next few days, the relationships between the guards and the prisoners changed, with a change in one leading to a change in the other. Remember that the guards were firmly in control and the prisoners were totally dependent on them.

As the prisoners became more dependent, the guards became more derisive towards them. They held the prisoners in contempt and let the prisoners know it. As the guards’ contempt for them grew, the prisoners became more submissive.

As the prisoners became more submissive, the guards became more aggressive and assertive. They demanded ever greater obedience from the prisoners. The prisoners were dependent on the guards for everything, so tried to find ways to please the guards, such as telling tales on fellow prisoners.

Prisoner #8612

Less than 36 hours into the experiment, Prisoner #8612 began suffering from acute emotional disturbance, disorganized thinking, uncontrollable crying, and rage.

After a meeting with the guards where they told him he was weak, but offered him “informant” status, #8612 returned to the other prisoners and said “You can”t leave. You can’t quit.”

Soon #8612 “began to act ‘crazy,’ to scream, to curse, to go into a rage that seemed out of control.” It wasn’t until this point that the psychologists realized they had to let him out.

A Visit from Parents

The next day, the guards held a visiting hour for parents and friends. They were worried that when the parents saw the state of the jail, they might insist on taking their sons home. Guards washed the prisoners, had them clean and polish their cells, fed them a big dinner and played music on the intercom.

After the visit, rumors spread of a mass escape plan. Afraid that they would lose the prisoners, the guards and experimenters tried to enlist help and facilities of the Palo Alto police department.

The guards again escalated the level of harassment, forcing them to do menial, repetitive work such as cleaning toilets with their bare hands.

Catholic Priest

Zimbardo invited a Catholic priest who had been a prison chaplain to evaluate how realistic our prison situation was. Half of the prisoners introduced themselves by their number rather than name.

The chaplain interviewed each prisoner individually. The priest told them the only way they would get out was with the help of a lawyer.

Prisoner #819

Eventually, while talking to the priest, #819 broke down and began to cry hysterically, just like two previously released prisoners had.

The psychologists removed the chain from his foot, the cap off his head, and told him to go and rest in a room that was adjacent to the prison yard. They told him they would get him some food and then take him to see a doctor.

While this was going on, one of the guards lined up the other prisoners and had them chant aloud:

“Prisoner #819 is a bad prisoner. Because of what Prisoner #819 did, my cell is a mess, Mr. Correctional Officer.”

The psychologists realized #819 could hear the chanting and went back into the room where they found him sobbing uncontrollably. The psychologists tried to get him to agree to leave the experiment, but he said he could not leave because the others had labeled him a bad prisoner.

Back to Reality

At that point, Zimbardo said, “Listen, you are not #819. You are [his name], and my name is Dr. Zimbardo. I am a psychologist, not a prison superintendent, and this is not a real prison. This is just an experiment, and those are students, not prisoners, just like you. Let’s go.”

He stopped crying suddenly, looked up and replied, “Okay, let’s go,“ as if nothing had been wrong.

An End to the Experiment

Zimbardo (1973) had intended that the experiment should run for two weeks, but on the sixth day, it was terminated, due to the emotional breakdowns of prisoners, and excessive aggression of the guards.

Christina Maslach, a recent Stanford Ph.D. brought in to conduct interviews with the guards and prisoners, strongly objected when she saw the prisoners being abused by the guards.

Filled with outrage, she said, “It’s terrible what you are doing to these boys!” Out of 50 or more outsiders who had seen our prison, she was the only one who ever questioned its morality.

Zimbardo (2008) later noted, “It wasn’t until much later that I realized how far into my prison role I was at that point — that I was thinking like a prison superintendent rather than a research psychologist.“

This led him to prioritize maintaining the experiment’s structure over the well-being and ethics involved, thereby highlighting the blurring of roles and the profound impact of the situation on human behavior.

Here’s a quote that illustrates how Philip Zimbardo, initially the principal investigator, became deeply immersed in his role as the “Stanford Prison Superintendent (April 19, 2011):

“By the third day, when the second prisoner broke down, I had already slipped into or been transformed into the role of “Stanford Prison Superintendent.” And in that role, I was no longer the principal investigator, worried about ethics. When a prisoner broke down, what was my job? It was to replace him with somebody on our standby list. And that’s what I did. There was a weakness in the study in not separating those two roles. I should only have been the principal investigator, in charge of two graduate students and one undergraduate.”

According to Zimbardo and his colleagues, the Stanford Prison Experiment revealed how people will readily conform to the social roles they are expected to play, especially if the roles are as strongly stereotyped as those of the prison guards.

Because the guards were placed in a position of authority, they began to act in ways they would not usually behave in their normal lives.

The “prison” environment was an important factor in creating the guards’ brutal behavior (none of the participants who acted as guards showed sadistic tendencies before the study).

Therefore, the findings support the situational explanation of behavior rather than the dispositional one.

Zimbardo proposed that two processes can explain the prisoner’s “final submission.”

Deindividuation may explain the behavior of the participants; especially the guards. This is a state when you become so immersed in the norms of the group that you lose your sense of identity and personal responsibility.

The guards may have been so sadistic because they did not feel what happened was down to them personally – it was a group norm. They also may have lost their sense of personal identity because of the uniform they wore.

Also, learned helplessness could explain the prisoner’s submission to the guards. The prisoners learned that whatever they did had little effect on what happened to them. In the mock prison the unpredictable decisions of the guards led the prisoners to give up responding.

After the prison experiment was terminated, Zimbardo interviewed the participants. Here’s an excerpt:

‘Most of the participants said they had felt involved and committed. The research had felt “real” to them. One guard said, “I was surprised at myself. I made them call each other names and clean the toilets out with their bare hands. I practically considered the prisoners cattle and I kept thinking I had to watch out for them in case they tried something.” Another guard said “Acting authoritatively can be fun. Power can be a great pleasure.” And another: “… during the inspection I went to Cell Two to mess up a bed which a prisoner had just made and he grabbed me, screaming that he had just made it and that he was not going to let me mess it up. He grabbed me by the throat and although he was laughing I was pretty scared. I lashed out with my stick and hit him on the chin although not very hard, and when I freed myself I became angry.”’

Most of the guards found it difficult to believe that they had behaved in the brutal ways that they had. Many said they hadn’t known this side of them existed or that they were capable of such things.

The prisoners, too, couldn’t believe that they had responded in the submissive, cowering, dependent way they had. Several claimed to be assertive types normally.

When asked about the guards, they described the usual three stereotypes that can be found in any prison: some guards were good, some were tough but fair, and some were cruel.

A further explanation for the behavior of the participants can be described in terms of reinforcement.  The escalation of aggression and abuse by the guards could be seen as being due to the positive reinforcement they received both from fellow guards and intrinsically in terms of how good it made them feel to have so much power.

Similarly, the prisoners could have learned through negative reinforcement that if they kept their heads down and did as they were told, they could avoid further unpleasant experiences.

Critical Evaluation

Ecological validity.

The Stanford Prison Experiment is criticized for lacking ecological validity in its attempt to simulate a real prison environment. Specifically, the “prison” was merely a setup in the basement of Stanford University’s psychology department.

The student “guards” lacked professional training, and the experiment’s duration was much shorter than real prison sentences. Furthermore, the participants, who were college students, didn’t reflect the diverse backgrounds typically found in actual prisons in terms of ethnicity, education, and socioeconomic status.

None had prior prison experience, and they were chosen due to their mental stability and low antisocial tendencies. Additionally, the mock prison lacked spaces for exercise or rehabilitative activities.

Demand characteristics

Demand characteristics could explain the findings of the study. Most of the guards later claimed they were simply acting. Because the guards and prisoners were playing a role, their behavior may not be influenced by the same factors which affect behavior in real life. This means the study’s findings cannot be reasonably generalized to real life, such as prison settings. I.e, the study has low ecological validity.

One of the biggest criticisms is that strong demand characteristics confounded the study. Banuazizi and Movahedi (1975) found that the majority of respondents, when given a description of the study, were able to guess the hypothesis and predict how participants were expected to behave.

This suggests participants may have simply been playing out expected roles rather than genuinely conforming to their assigned identities.

In addition, revelations by Zimbardo (2007) indicate he actively encouraged the guards to be cruel and oppressive in his orientation instructions prior to the start of the study. For example, telling them “they [the prisoners] will be able to do nothing and say nothing that we don’t permit.”

He also tacitly approved of abusive behaviors as the study progressed. This deliberate cueing of how participants should act, rather than allowing behavior to unfold naturally, indicates the study findings were likely a result of strong demand characteristics rather than insightful revelations about human behavior.

However, there is considerable evidence that the participants did react to the situation as though it was real. For example, 90% of the prisoners’ private conversations, which were monitored by the researchers, were on the prison conditions, and only 10% of the time were their conversations about life outside of the prison.

The guards, too, rarely exchanged personal information during their relaxation breaks – they either talked about ‘problem prisoners,’ other prison topics, or did not talk at all. The guards were always on time and even worked overtime for no extra pay.

When the prisoners were introduced to a priest, they referred to themselves by their prison number, rather than their first name. Some even asked him to get a lawyer to help get them out.

Fourteen years after his experience as prisoner 8612 in the Stanford Prison Experiment, Douglas Korpi, now a prison psychologist, reflected on his time and stated (Musen and Zimbardo 1992):

“The Stanford Prison Experiment was a very benign prison situation and it promotes everything a normal prison promotes — the guard role promotes sadism, the prisoner role promotes confusion and shame”.

Sample bias

The study may also lack population validity as the sample comprised US male students. The study’s findings cannot be applied to female prisons or those from other countries. For example, America is an individualist culture (where people are generally less conforming), and the results may be different in collectivist cultures (such as Asian countries).

Carnahan and McFarland (2007) have questioned whether self-selection may have influenced the results – i.e., did certain personality traits or dispositions lead some individuals to volunteer for a study of “prison life” in the first place?

All participants completed personality measures assessing: aggression, authoritarianism, Machiavellianism, narcissism, social dominance, empathy, and altruism. Participants also answered questions on mental health and criminal history to screen out any issues as per the original SPE.

Results showed that volunteers for the prison study, compared to the control group, scored significantly higher on aggressiveness, authoritarianism, Machiavellianism, narcissism, and social dominance. They scored significantly lower on empathy and altruism.

A follow-up role-playing study found that self-presentation biases could not explain these differences. Overall, the findings suggest that volunteering for the prison study was influenced by personality traits associated with abusive tendencies.

Zimbardo’s conclusion may be wrong

While implications for the original SPE are speculative, this lends support to a person-situation interactionist perspective, rather than a purely situational account.

It implies that certain individuals are drawn to and selected into situations that fit their personality, and that group composition can shape behavior through mutual reinforcement.

Contributions to psychology

Another strength of the study is that the harmful treatment of participants led to the formal recognition of ethical  guidelines by the American Psychological Association. Studies must now undergo an extensive review by an institutional review board (US) or ethics committee (UK) before they are implemented.

Most institutions, such as universities, hospitals, and government agencies, require a review of research plans by a panel. These boards review whether the potential benefits of the research are justifiable in light of the possible risk of physical or psychological harm.

These boards may request researchers make changes to the study’s design or procedure, or, in extreme cases, deny approval of the study altogether.

Contribution to prison policy

A strength of the study is that it has altered the way US prisons are run. For example, juveniles accused of federal crimes are no longer housed before trial with adult prisoners (due to the risk of violence against them).

However, in the 25 years since the SPE, U.S. prison policy has transformed in ways counter to SPE insights (Haney & Zimbardo, 1995):

• Rehabilitation was abandoned in favor of punishment and containment. Prison is now seen as inflicting pain rather than enabling productive re-entry.
• Sentencing became rigid rather than accounting for inmates’ individual contexts. Mandatory minimums and “three strikes” laws over-incarcerate nonviolent crimes.
• Prison construction boomed, and populations soared, disproportionately affecting minorities. From 1925 to 1975, incarceration rates held steady at around 100 per 100,000. By 1995, rates tripled to over 600 per 100,000.
• Drug offenses account for an increasing proportion of prisoners. Nonviolent drug offenses make up a large share of the increased incarceration.
• Psychological perspectives have been ignored in policymaking. Legislators overlooked insights from social psychology on the power of contexts in shaping behavior.
• Oversight retreated, with courts deferring to prison officials and ending meaningful scrutiny of conditions. Standards like “evolving decency” gave way to “legitimate” pain.
• Supermax prisons proliferated, isolating prisoners in psychological trauma-inducing conditions.

The authors argue psychologists should reengage to:

• Limit the use of imprisonment and adopt humane alternatives based on the harmful effects of prison environments
• Assess prisons’ total environments, not just individual conditions, given situational forces interact
• Prepare inmates for release by transforming criminogenic post-release contexts
• Address socioeconomic risk factors, not just incarcerate individuals
• Develop contextual prediction models vs. focusing only on static traits
• Scrutinize prison systems independently, not just defer to officials shaped by those environments
• Generate creative, evidence-based reforms to counter over-punitive policies

Psychology once contributed to a more humane system and can again counter the U.S. “rage to punish” with contextual insights (Haney & Zimbardo, 1998).

Evidence for situational factors

Zimbardo (1995) further demonstrates the power of situations to elicit evil actions from ordinary, educated people who likely would never have done such things otherwise. It was another situation-induced “transformation of human character.”

• Unit 731 was a covert biological and chemical warfare research unit of the Japanese army during WWII.
• It was led by General Shiro Ishii and involved thousands of doctors and researchers.
• Unit 731 set up facilities near Harbin, China to conduct lethal human experimentation on prisoners, including Allied POWs.
• Experiments involved exposing prisoners to things like plague, anthrax, mustard gas, and bullets to test biological weapons. They infected prisoners with diseases and monitored their deaths.
• At least 3,000 prisoners died from these brutal experiments. Many were killed and dissected.
• The doctors in Unit 731 obeyed orders unquestioningly and conducted these experiments in the name of “medical science.”
• After the war, the vast majority of doctors who participated faced no punishment and went on to have prestigious careers. This was largely covered up by the U.S. in exchange for data.
• It shows how normal, intelligent professionals can be led by situational forces to systematically dehumanize victims and conduct incredibly cruel and lethal experiments on people.
• Even healers trained to preserve life used their expertise to destroy lives when the situational forces compelled obedience, nationalism, and wartime enmity.

Evidence for an interactionist approach

The results are also relevant for explaining abuses by American guards at Abu Ghraib prison in Iraq.

An interactionist perspective recognizes that volunteering for roles as prison guards attracts those already prone to abusive tendencies, which are intensified by the prison context.

This counters a solely situationist view of good people succumbing to evil situational forces.

Ethical Issues

The study has received many ethical criticisms, including lack of fully informed consent by participants as Zimbardo himself did not know what would happen in the experiment (it was unpredictable). Also, the prisoners did not consent to being “arrested” at home. The prisoners were not told partly because final approval from the police wasn’t given until minutes before the participants decided to participate, and partly because the researchers wanted the arrests to come as a surprise. However, this was a breach of the ethics of Zimbardo’s own contract that all of the participants had signed.

Protection of Participants

Participants playing the role of prisoners were not protected from psychological harm, experiencing incidents of humiliation and distress. For example, one prisoner had to be released after 36 hours because of uncontrollable bursts of screaming, crying, and anger.

Here’s a quote from Philip G. Zimbardo, taken from an interview on the Stanford Prison Experiment’s 40th anniversary (April 19, 2011):

“In the Stanford prison study, people were stressed, day and night, for 5 days, 24 hours a day. There’s no question that it was a high level of stress because five of the boys had emotional breakdowns, the first within 36 hours. Other boys that didn’t have emotional breakdowns were blindly obedient to corrupt authority by the guards and did terrible things to each other. And so it is no question that that was unethical. You can’t do research where you allow people to suffer at that level.”

“After the first one broke down, we didn’t believe it. We thought he was faking. There was actually a rumor he was faking to get out. He was going to bring his friends in to liberate the prison. And/or we believed our screening procedure was inadequate, [we believed] that he had some mental defect that we did not pick up. At that point, by the third day, when the second prisoner broke down, I had already slipped into or been transformed into the role of “Stanford Prison Superintendent.” And in that role, I was no longer the principal investigator, worried about ethics.”

However, in Zimbardo’s defense, the emotional distress experienced by the prisoners could not have been predicted from the outset.

Approval for the study was given by the Office of Naval Research, the Psychology Department, and the University Committee of Human Experimentation.

This Committee also did not anticipate the prisoners’ extreme reactions that were to follow. Alternative methodologies were looked at that would cause less distress to the participants but at the same time give the desired information, but nothing suitable could be found.

Withdrawal 

Although guards were explicitly instructed not to physically harm prisoners at the beginning of the Stanford Prison Experiment, they were allowed to induce feelings of boredom, frustration, arbitrariness, and powerlessness among the inmates.

This created a pervasive atmosphere where prisoners genuinely believed and even reinforced among each other, that they couldn’t leave the experiment until their “sentence” was completed, mirroring the inescapability of a real prison.

Even though two participants (8612 and 819) were released early, the impact of the environment was so profound that prisoner 416, reflecting on the experience two months later, described it as a “prison run by psychologists rather than by the state.”

Extensive group and individual debriefing sessions were held, and all participants returned post-experimental questionnaires several weeks, then several months later, and then at yearly intervals. Zimbardo concluded there were no lasting negative effects.

Zimbardo also strongly argues that the benefits gained from our understanding of human behavior and how we can improve society should outbalance the distress caused by the study.

However, it has been suggested that the US Navy was not so much interested in making prisons more human and were, in fact, more interested in using the study to train people in the armed services to cope with the stresses of captivity.

Discussion Questions

What are the effects of living in an environment with no clocks, no view of the outside world, and minimal sensory stimulation?

Consider the psychological consequences of stripping, delousing, and shaving the heads of prisoners or members of the military. Whattransformations take place when people go through an experience like this?

The prisoners could have left at any time, and yet, they didn’t. Why?

After the study, how do you think the prisoners and guards felt?

If you were the experimenter in charge, would you have done this study? Would you have terminated it earlier? Would you have conducted a follow-up study?

Frequently Asked Questions

What happened to prisoner 8612 after the experiment.

Douglas Korpi, as prisoner 8612, was the first to show signs of severe distress and demanded to be released from the experiment. He was released on the second day, and his reaction to the simulated prison environment highlighted the study’s ethical issues and the potential harm inflicted on participants.

After the experiment, Douglas Korpi graduated from Stanford University and earned a Ph.D. in clinical psychology. He pursued a career as a psychotherapist, helping others with their mental health struggles.

Why did Zimbardo not stop the experiment?

Zimbardo did not initially stop the experiment because he became too immersed in his dual role as the principal investigator and the prison superintendent, causing him to overlook the escalating abuse and distress among participants.

It was only after an external observer, Christina Maslach, raised concerns about the participants’ well-being that Zimbardo terminated the study.

What happened to the guards in the Stanford Prison Experiment?

In the Stanford Prison Experiment, the guards exhibited abusive and authoritarian behavior, using psychological manipulation, humiliation, and control tactics to assert dominance over the prisoners. This ultimately led to the study’s early termination due to ethical concerns.

What did Zimbardo want to find out?

Zimbardo aimed to investigate the impact of situational factors and power dynamics on human behavior, specifically how individuals would conform to the roles of prisoners and guards in a simulated prison environment.

He wanted to explore whether the behavior displayed in prisons was due to the inherent personalities of prisoners and guards or the result of the social structure and environment of the prison itself.

What were the results of the Stanford Prison Experiment?

The results of the Stanford Prison Experiment showed that situational factors and power dynamics played a significant role in shaping participants’ behavior. The guards became abusive and authoritarian, while the prisoners became submissive and emotionally distressed.

The experiment revealed how quickly ordinary individuals could adopt and internalize harmful behaviors due to their assigned roles and the environment.

Banuazizi, A., & Movahedi, S. (1975). Interpersonal dynamics in a simulated prison: A methodological analysis. American Psychologist, 30 , 152-160.

Carnahan, T., & McFarland, S. (2007). Revisiting the Stanford prison experiment: Could participant self-selection have led to the cruelty? Personality and Social Psychology Bulletin, 33, 603-614.

Drury, S., Hutchens, S. A., Shuttlesworth, D. E., & White, C. L. (2012). Philip G. Zimbardo on his career and the Stanford Prison Experiment’s 40th anniversary.  History of Psychology ,  15 (2), 161.

Griggs, R. A., & Whitehead, G. I., III. (2014). Coverage of the Stanford Prison Experiment in introductory social psychology textbooks. Teaching of Psychology, 41 , 318 –324.

Haney, C., Banks, W. C., & Zimbardo, P. G. (1973). A study of prisoners and guards in a simulated prison . Naval Research Review , 30, 4-17.

Haney, C., & Zimbardo, P. (1998). The past and future of U.S. prison policy: Twenty-five years after the Stanford Prison Experiment.  American Psychologist, 53 (7), 709–727.

Musen, K. & Zimbardo, P. (1992) (DVD) Quiet Rage: The Stanford Prison Experiment Documentary.

Zimbardo, P. G. (Consultant, On-Screen Performer), Goldstein, L. (Producer), & Utley, G. (Correspondent). (1971, November 26). Prisoner 819 did a bad thing: The Stanford Prison Experiment [Television series episode]. In L. Goldstein (Producer), Chronolog. New York, NY: NBC-TV.

Zimbardo, P. G. (1973). On the ethics of intervention in human psychological research: With special reference to the Stanford prison experiment.  Cognition ,  2 (2), 243-256.

Zimbardo, P. G. (1995). The psychology of evil: A situationist perspective on recruiting good people to engage in anti-social acts.  Japanese Journal of Social Psychology ,  11 (2), 125-133.

Zimbardo, P.G. (2007). The Lucifer effect: Understanding how good people turn evil . New York, NY: Random House.

Further Information

• Reicher, S., & Haslam, S. A. (2006). Rethinking the psychology of tyranny: The BBC prison study. The British Journal of Social Psychology, 45 , 1.
• Coverage of the Stanford Prison Experiment in introductory psychology textbooks
• The Stanford Prison Experiment Official Website

Watch CBS News

Shocking "prison" study 40 years later: What happened at Stanford?

December 27, 2011 / 11:15 AM EST / CBS News

It's considered one of the most notorious psychology experiments ever conducted - and for good reason. The "Stanford prison experiment" - conducted in Palo Alto, Calif. 40 years ago - was conceived by Dr. Philip G. Zimbardo as a way to use ordinary college students to explore the often volatile dynamic that exists between prisoners and prison guards - and as a means of encouraging reforms in the way real-life prison guards are trained.

But what started out as make-believe quickly devolved into an all-too-real prison situation. Some student "guards" became sadistic overlords who eagerly abused the "prisoners," many of whom began to see themselves as real prisoners.

Just what happened in the basement of the Stanford psychology department all those years ago? Keep clicking for a glimpse back in time...

It all started with a newspaper ad: "Male college students needed for psychological study of prison life." Dr. Philip Zimbardo and his team selected 24 college students and offered them $15 per day for the two-week study. A coin-flip would decide who would be "prisoner" or "guard." Nobody, including Zimbardo, had any idea what was in store.

On a quiet Sunday in August, Zimbardo enlisted real Palo Alto police officers to help kick off the study - by arresting students from their homes for armed robbery. The idea was to make the experience as "real" as possible.

The students were read their rights, frisked, cuffed, then carted off to the Palo Alto police station.

At the police station, "suspects" were fingerprinted, read their charges, blindfolded, and taken to a holding cell to await transportation to the "prison" at Stanford.

While the "suspects" were being rounded up by the real-world police, Zimbardo and his team put the finishing touches on the "prison." They nailed bars on cells and set up a closet for solitary confinement - known as "the hole." Real ex-cons served as consultants to make things as realistic as possible.

A hidden video camera was installed, and cells were bugged so the researchers could see and hear what was happening at all times.

Many of the "prisoners" were still reeling from the surprise arrests when they arrived at the "prison." But things quickly grew even worse for the "prisoners," as they were stripped naked and "deloused" with a spray.

Each "prisoner" was issued a smock with ID number, stocking cap, rubber sandals - and each had a chain bolted to his ankle. The chain was to remind "prisoners" at all times that they were incarcerated and unable to escape.

"Guards" wore khakis, mirrored sunglasses, and carried around a whistle and a baton. They were untrained, free to do whatever they deemed necessary to maintain law and order. Some played nice, but others grew increasingly sadistic.

"Prisoners" expected some harassment and a poor diet when they volunteered. But they didn't expect to be rudely awakened at 2:30 a.m. the first night and forced to line up for roll call. "Guards" asserted authority by forcing "prisoners" to memorize their prison numbers and do push-ups.

On the second day of the experiment, the "prisoners" barricaded themselves in their cells, ripped off their numbers and caps, and began taunting the "guards." That surprised the researchers.

The "guards" responded by shooting fire extinguishes at the "prisoners," and then stripping the "prisoners" naked and removing their beds. "Guards" tossed the rebellion's leader into "the hole."

When the "guards" realized they couldn't always physically control their "prisoners," they turned to psychological tactics. The "guards" set up a "privilege cell" where the most cooperative "prisoners" got their clothes and beds back and were allowed to wash, brush their teeth, eat, and sleep.

"Guards" soon denied "prisoners" the right to use the bathroom, providing buckets. Emptying the bucket? That privilege was granted only to cooperative "prisoners."

"Prisoners" believed the "guards" were chosen because they were bigger and stronger. In reality, there was no height difference between the groups.

"Guards" put paper bags on the prisoners as they walked around - just one of many dehumanizing tactics.

This "prisoner," No. 8612, went into a fit of rage less than 36 hours into the experiment, telling his fellow "prisoners" that they couldn't quit the experiment. It wasn't true, of course, but the message seemed to terrify the other "prisoners."

Zimbardo set up visiting hours with some of the "prisoners''" friends and family. He had the "prisoners" clean themselves and their cells, and fed them a big meal so worried parents wouldn't insist that their kids leave the study. Some parents nevertheless complained to Zimbardo - but he brushed off their concerns.

Rumors soon spread that prisoner #8612, who had been released following his outbursts, was arranging a prison break to free the "prisoners." When Zimbardo caught wind of the plan, he tried unsuccessfully to arrange for the "prisoners" to be transferred to a real prison. "Guards" blindfolded "prisoners" and led them to a different floor.

Zimbardo waited all night, but the prison break never materialized. Like his study's participants, Zimbardo seemed to have blurred the lines between reality and make-believe, by acting like a real-world prison superintendent.

After the rumored jail break, the "guards" escalated their harassment of the "prisoners." They upped the number of jumping jacks and push-ups the "prisoners" were told to do, and forced them to do unpleasant tasks, including scrubbing toilets.

Zimbardo called in a priest to interview "prisoners," just as it might hapen in a real prison. To Zimbardo's amazement, "prisoners" introduced themselves to the priest not by their names but by their prison numbers.

When the priest asked "prisoners" why they were in jail, or if they needed a lawyer, some took him up on the offer.

More "prisoners" succumbed to the harsh conditions inside the "prison." One stopped eating and cried hysterically. Zimbardo told him he could leave the study, but he declined - saying he didn't want the others to believe he was a bad "prisoner."

No prison experience is complete without going before the parole board. But this "board" was made up of psychology department secretaries and graduate students. They met with "prisoners" who thought they had grounds for parole. The "prisoners" seemed to forget that they could leave anytime they wanted. Said Zimbardo, "Their sense of reality had shifted."

Five days into the experiment, some "guards" calmed down and became "good guys." But others kept up their brutal treatment of the "prisoners," including one notoriously tough "guard" the "prisoners" nicknamed "John Wayne."

Parents eventually called Zimbardo, asking if they could contact a lawyer to get their kids out of "prison." The calls, combined with the increasingly abusive treatment of the "prisoners," convinced Zimbardo that the experiment had gone too far. But Zimbardo ended the experiment only after being admonished by a newly minted PhD who had returned to Stanford and was shocked by what she saw.

The experiment was certainly shocking, but did it bring about the sorts of prison reforms that Zimbardo had hoped for? Not really. "Research and knowledge rarely changes systems," Zimbardo told CBS News in an email.

But the experiment has been cited again and again over the years - for example, by experts trying to explain the 1971 riots at Attica Correctional Facility in New York, or even the dehumanizing photos that came out of Iraq's Abu Ghraib in 2003.

What's more, as Zimbardo points out, just about everyone fills the role of "prisoner" or "guard" at some point in their lives - as when a boss restricts the actions of his/her subordinates or a parent disciplines a child. And it's in these roles that we live up to - or down to - our own expectations. As Zimbardo puts it, "Human behavior is under situational control more than we imagine or want to believe and admit."

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Stanford Prison Experiment

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Stanford Prison Experiment , a social psychology study in which college students became prisoners or guards in a simulated prison environment . The experiment, funded by the U.S. Office of Naval Research, took place at Stanford University in August 1971. It was intended to measure the effect of role-playing, labeling, and social expectations on behaviour over a period of two weeks. However, mistreatment of prisoners escalated so alarmingly that principal investigator Philip G. Zimbardo terminated the experiment after only six days.

More than 70 young men responded to an advertisement about a “psychological study of prison life,” and experimenters selected 24 applicants who were judged to be physically and mentally healthy. The paid subjects—they received $15 a day—were divided randomly into equal numbers of guards and prisoners. Guards were ordered not to physically abuse prisoners and were issued mirrored sunglasses that prevented any eye contact. Prisoners were “arrested” by actual police and handed over to the experimenters in a mock prison in the basement of a campus building. Prisoners were then subjected to indignities that were intended to simulate the environment of a real-life prison. In keeping with Zimbardo’s intention to create very quickly an “atmosphere of oppression,” each prisoner was made to wear a “dress” as a uniform and to carry a chain padlocked around one ankle. All participants were observed and videotaped by the experimenters.

On only the second day the prisoners staged a rebellion. Guards then worked out a system of rewards and punishments to manage the prisoners. Within the first four days, three prisoners had become so traumatized that they were released. Over the course of the experiment, some of the guards became cruel and tyrannical, while a number of the prisoners became depressed and disoriented. However, only after an outside observer came upon the scene and registered shock did Zimbardo conclude the experiment, less than a week after it had started.

The Stanford Prison Experiment immediately came under attack on methodological and ethical grounds. Zimbardo admitted that during the experiment he had sometimes felt more like a prison superintendent than a research psychologist. Later on, he claimed that the experiment’s “social forces and environmental contingencies” had led the guards to behave badly. However, others claimed that the original advertisement attracted people who were predisposed to authoritarianism . The most conspicuous challenge to the Stanford findings came decades later in the form of the BBC Prison Study, a differently organized experiment documented in a British Broadcasting Corporation series called The Experiment (2002). The BBC’s mock prisoners turned out to be more assertive than Zimbardo’s. The British experimenters called the Stanford experiment “a study of what happens when a powerful authority figure (Zimbardo) imposes tyranny.”

The Stanford Prison Experiment became widely known outside academia . It was the acknowledged inspiration for Das Experiment (2001), a German movie that was remade in the United States as the direct-to-video film The Experiment (2010). The Stanford Prison Experiment (2015) was created with Zimbardo’s active participation; the dramatic film more closely followed actual events.

The Stanford Prison Experiment: The Power of the Situation

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Philip Zimbardo is best known for his 1971 Stanford Prison Experiment (SPE). Early in his career, he conducted experiments in the psychology of deindividualization, in which a person in a group or crowd no longer acts as a responsible individual but is swept along and participates in antisocial actions. After moving to Stanford University, he began to focus on institutional power over the individual in group settings, such as long-term care facilities for the elderly and prisons. His research proposal for a simulated prison was approved by the Stanford University Human Subjects Research Review Committee in July 1971. He built a mock prison in the basement of the University’s psychology building and recruited college-aged male subjects to play prisoners and guards. The study began on Sunday, August 8th, and was to run for 2 weeks but ended on Friday morning August 13th. In less than a week, several of the mock guards hazed and brutalized the mock prisoners, some of whom found ways of coping, while others exhibited symptoms of mental breakdown.

The degree of civilization in a society can be judged by entering its prisons. — attributed to Fyodor Dostoevsky, The House of the Dead

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I wish to thank Chris Herrera, Jonathan K. Rosen, David Segal and Ruth Spivak for their comments on this chapter.

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Stanford Prison Experiment

In 2015, The Stanford Prison Experiment was released in theaters. The movie detailed an infamous 1971 experiment in which 24 college students were “put in prison.” While the “experiment” was supposed to last for two weeks, it was terminated after just six days due to the psychological effects it was having on both the “guards” and “prisoners.”

So what actually happened during the Stanford Prison Experiment? Why is it so infamous? Does the movie get everything right, or is it just a dramatization? Find out for yourself. 

What Was the Stanford Prison Experiment?

After Stanley Milgram’s experiment rocked the world of psychology, many people were left with questions about obedience, power dynamics, and the abuse of power. Philip Zimbardo, a professor at Stanford, wanted to explore these questions further. With a grant from the Navy, Zimbardo set up the Stanford Prison Experiment.

Could a person’s role influence their behavior? This is the question Philip Zimbardo wanted to answer.

How Was the Stanford Prison Experiment Conducted?

Zimbardo and his team interviewed 70 applicants at Stanford who were willing to participate in the study for 14 days and receive $15 a day. They wanted to make sure that they chose the brightest and most mentally sound participants. After narrowing their applicants down to 24, the researchers flipped a coin and assigned the roles. Half of the participants would be prisoners and half would be guards. 

The researchers then set up a basement at Stanford to look like a real prison. They were very serious about treating the experiment like a simulation. Prisoners were “arrested” in public and taken into the prison. (They were even booked, fingerprinted, and strip searched.) 

Zimbardo’s team also gave prisoners numbers that they were meant to use instead of their real name. They claimed that it would help give the prisoners a sense of anonymity and help the experiment. 

Guards had pretty much free reign on how they could treat the prisoner, although they had two main rules:

• Guards could not hit the prisoners
• Guards could not put prisoners in solitary confinement (“the hole”) for more than an hour

Zimbardo played the role of prison superintendent. His graduate students and research partners also played roles as members of the “parole board” and the prison warden. 

Prisoners were tasked with certain activities like writing a letter home to their “visitors” and making a case to the parole board about why they should be let off. Guards also subjected the prisoners to “counts” in which they forced the prisoners to do jumping jacks, push-ups, and degrading tasks. 

How Long Did the Stanford Prison Experiment Last? 

It did not take long for the guards to abuse their power. Within one day, a guard hit one of the prisoners with his nightstick.

On the second day, the prisoners tried to rebel and their beds were taken away. To punish the prisoners, the guards shot a fire extinguisher into the cell. Guards used physical and psychological abuse, including sleep deprivation, to punish and intimidate the prisoners throughout the study.

The prisoners were forced to wear dressings and stocking caps the whole time. At some points, guards would put bags over the prisoners’ heads. Since the study has ended, it has been compared to actions at the Abu Ghraib detention center - Zimbardo has written about the case and its parallels to the prison experiment since. 

Why Did It Get Shut Down? 

Very quickly, the guards started to abuse their power. The prisoners started to spiral. On the third day, Prisoner #8612 started to cry and scream uncontrollably. He threatened to harm himself and call a lawyer. To avoid potential psychological damage or a lawsuit, he was let go. Two other prisoners were let go in the next two days. One had refused to eat. 

On the fifth day, Zimbardo’s girlfriend (and former student) came to visit the experiment. Zimbardo and his team had been monitoring the experiment, and playing their roles in it, 24/7. When she saw the horrors of what was going on in the prison, she asked Zimbardo to end the “experiment” immediately. She even threatened to break up with him. 

On the sixth day, Zimbardo ended the experiment. 

Stanford Prison Experiment Movie 

In 2015, a movie about the Stanford Prison Experiment was released on Netflix. The movie is no longer streaming on Netflix, but you can order the DVD version if you want to watch it. Although all movies based on true events are seen through a specific point of view, critics say that this is a very accurate portrayal of what happened during the experiment. 

Why Was the Stanford Prison Experiment Unethical?

This experiment showed the world just how quickly people can abuse power when it’s given to them. But it remains as one of the most controversial experiments in the world of social psychology . There are a few reasons why. 

The first obvious one is the psychological abuse that the prisoners endured during the study. Is it ethical to put human subjects through that kind of distress and trauma, so much so that many couldn’t endure the experiment? 

(Zimbardo claims that none of the participants have suffered long-term psychological consequences from their participation.) 

Was The Stanford Prison Experiment Fake?

In more recent years, critics have also come forward to say that the results were not as “natural” as Zimbardo and his team may want you to think. Transcripts and audio recordings from the Stanford Prison Experiment show that Zimbardo’s team “coached” guards. They told them to be “tough” for the sake of the experiment. 

Even the prisoners may have been “faking” their responses. Prisoner #8612, who is most well-known for his blood-curdling “I’m burning up inside!” has come forward to say that his time in the Stanford County Jail was more of an “improv exercise.” Many critics have likened the experiment to a drama rather than a legitimate psychology experiment. 

Carlo Prescott, the experiment’s prison consultant, has also come forward to say that the experiment’s more cruel treatments were not naturally thought up and executed by the guards alone. He wrote the following in an op-ed:

“Ideas such as bags being placed over the heads of prisoners, inmates being bound together with chains and buckets being used in place of toilets in their cells were all experiences of mine at the old "Spanish Jail" section of San Quentin and which I dutifully shared with the Stanford Prison Experiment braintrust months before the experiment started. To allege that all these carefully tested, psychologically solid, upper-middle-class Caucasian "guards" dreamed this up on their own is absurd.” 

The Lasting Effect of the Stanford Prison Experiment 

The Stanford Prison Experiment seems to have raised more questions than it answered. Where should psychologists draw the line when it comes to subjecting participants to distress? How easily can psychologists blur the lines of “experiment” vs. “simulation” or “drama?” And if the Stanford Prison Experiment didn’t exactly answer its original questions about power dynamics and obedience , what similar experiments can? How can the Stanford Prison experiment be improved? 

These are just some of the questions that psychologists face today. Maybe your work can help to figure out the answers!

Related posts:

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• The Monster Study (Summary, Results, and Ethical Issues)
• Beck’s Depression Inventory (BDI Test)
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• Published: 22 July 2015

Experimental psychology: The anatomy of obedience

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Brendan Maher reviews two films probing notorious US psychological experiments.

The Stanford Prison Experiment

Director: Kyle Patrick Alvarez. Sandbar Pictures/Abandon/Coup d'Etat: 2015

Experimenter

Director: Michael Almereyda. BB Film/FJ Productions/Intrinsic Value/Jeff Rice/2B: 2015.

Would you rather be a prisoner or a guard? In 1971, many of the 24 volunteers for an unusual psychological experiment at Stanford University in California said that they would prefer the former. “Nobody likes guards,” answered one. Ultimately, a coin flip determined the roles that these students took in the Stanford Prison Experiment, a notorious investigation of obedience and power run by psychologist Philip Zimbardo and commissioned by the US Office of Naval Research. A chilling film of the same name, directed by Kyle Patrick Alvarez, is now on limited release. Meanwhile, Michael Almereyda's Experimenter explores the work of social psychologist Stanley Milgram, whose infamous 1961 experiment on obedience to authority stands as a shocking example of how well-intentioned people can be convinced to harm others.

These experiments spanned a decade of US political upheaval. Milgram's was a response to the trial of Adolf Eichmann, one of the prime organizers of the Holocaust, whose unsuccessful defence was that he was following orders. Zimbardo's experiment took place as reports of atrocities by US soldiers filtered back from the Vietnam War. Interpretations have long been debated, but both experiments haunt the imagination by putting extreme behaviour on display.

The Stanford Prison Experiment is stark and claustrophobic, much like the makeshift 'prison' that Zimbardo and his colleagues constructed in the Stanford psychology department's basement. The screenplay is adapted from Zimbardo's The Lucifer Effect (Random House, 2007), which aimed to explain how situations and group effects can bring about evil behaviours. The film traces the experiment from volunteer recruitment until day six, when Zimbardo, concerned for the prisoners' well-being, shut it down prematurely.

A handful of documentaries have explored the study's findings and legacy, but Alvarez captures something intimate and atmospheric that cannot be gleaned from grainy videos or interviews. The 1970s are certainly there: the hair, the polyester and the lax research oversight. There are also subtle emotional moments, such as when cocksure humour drains from the face of 'prisoner 8612' as he is instructed to strip naked for delousing.

Zimbardo intended to explore how prisoners adapt to powerlessness, but he has contended that the experiment demonstrates how swiftly arbitrary assignment of power can lead to abuse. It has been invoked as paralleling the harm done to Iraqi detainees at the US-run Abu Ghraib prison in 2003: several guards in the film verbally taunt prisoners, restrict access to basic necessities and resort to sexual humiliation. One guard, nicknamed John Wayne, adopts the affect and southern drawl of the sadistic prison captain in the 1967 film Cool Hand Luke , preying undeterred on the weaknesses of 8612 in particular.

The prisoners, at first rebellious, are broken by the guards and pitted against one another; the experimenters themselves lose perspective. When 8612 begs to be released, Zimbardo and his colleagues initially refuse, convinced that he is faking his distress — even though that should not override the voluntary nature of the experiment. Several subjects, all screened as emotionally well grounded, have breakdowns; rather than fear for their well-being, Zimbardo develops a paranoid belief that outside forces will shut “his prison”. Finally, psychology PhD student Christina Maslach (later Zimbardo's wife) persuades him to change his mind after seeing the prisoners, half-naked and chained together, with bags over their heads, on a trip to the toilet. She tells Zimbardo: “Those are boys, and you are harming them.” The next day, as guards force prisoners to pantomime sexual intercourse, Zimbardo tells them that it is time to go home.

The film pulls few punches regarding Zimbardo's behaviour. This is consistent with his confession, in The Lucifer Effect , that he failed to provide “adequate oversight and surveillance when it was required ... the findings came at the expense of human suffering”. He wrote, “I am sorry for that and to this day apologize for contributing to this inhumanity.” The study was subsequently deemed to fall within existing ethical guidelines.

Others have wondered, however, whether Zimbardo oversold the results. When I contacted the real-life 'John Wayne', Dave Eshelman, he said that the experiment reveals no generalizable truths about humans' propensity for evil, and that he was playing a part, running his own experiment to see how far he could push people. “I figured I was doing them a favour by trying to force some results.” At least one other guard has said that Zimbardo went out of his way to create tension.

Milgram, too, has a complex legacy, as Experimenter reveals. Through an imaginative structure, the film explores several of his contributions to behavioural psychology. But he is best known for his electroshock experiments at Yale University in New Haven, Connecticut, a decade before Zimbardo's experiment. In them, an authority figure asked volunteers to administer what they were told were increasingly painful electric shocks to an actor who they believed was another volunteer. Two-thirds maxed out the voltage despite the actor's anguished cries.

It was difficult for many to come to terms with the results — including some of the research subjects, who were unhappy about the deception (Milgram preferred “illusion”). Almereyda playfully gives the audience a backseat view of the psychologist's approach. There are scenes in which Peter Sarsgaard, playing Milgram, speaks directly to camera — an homage to Milgram's own films explaining his experiments. This is a work, as the title implies, much more about the experimenter than about the experiment. Zimbardo has spoken of meeting Milgram, who “embraced me and said, 'I'm so happy you did this because now you can take off some of the heat of having done the most unethical study'.”

The shared legacies of the researchers can be seen in updated regulations for psychological research on human subjects, which prevent the kind of deception that Milgram perpetrated and the unstructured opportunity for abuse that Zimbardo created. But their experiments will always hold captive a dark part of the human imagination as we wonder just what kind of pain we would be willing to inflict on other human beings.

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Maher, B. Experimental psychology: The anatomy of obedience. Nature 523 , 408–409 (2015). https://doi.org/10.1038/523408a

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SOC101: Introduction to Sociology (2020.A.01)

The stanford prison experiment.

Read this article on the Stanford Prison Experiment. Philip Zimbardo is a social psychologist who wanted to research the effects of power structures and labeling in a prison setting. To do so, he experimented with college students by creating a prison-like experience. What does this experiment tell us about power and authority? What does it tell us about obedience and conformity?

Purpose of the Study

Zimbardo and his colleagues (1973) were interested in finding out whether the brutality reported among guards in American prisons was due to the sadistic personalities of the guards (i.e., dispositional) or had more to do with the prison environment (i.e., situational).

For example, prisoner and guards may have personalities which make conflict inevitable, with prisoners lacking respect for law and order and guards being domineering and aggressive. Alternatively, prisoners and guards may behave in a hostile manner due to the rigid power structure of the social environment in prisons. Zimbardo predicted the situation made people act the way they do rather than their disposition (personality).

To study the roles people play in prison situations, Zimbardo converted a basement of the Stanford University psychology building into a mock prison.

He advertised asking for volunteers to participate in a study of the psychological effects of prison life.

24 men judged to be the most physically & mentally stable, the most mature, & the least involved in antisocial behaviors were chosen to participate. The participants did not know each other prior to the study and were paid $15 per day to take part in the experiment. Participants were randomly assigned to either the role of prisoner or guard in a simulated prison environment. There were two reserves, and one dropped out, finally leaving ten prisoners and 11 guards. Prisoners were treated like every other criminal, being arrested at their own homes, without warning, and taken to the local police station. They were fingerprinted, photographed and 'booked'. Then they were blindfolded and driven to the psychology department of Stanford University, where Zimbardo had had the basement set out as a prison, with barred doors and windows, bare walls and small cells. Here the deindividuation process began. When the prisoners arrived at the prison they were stripped naked, deloused, had all their personal possessions removed and locked away, and were given prison clothes and bedding. They were issued a uniform, and referred to by their number only.

The use of ID numbers was a way to make prisoners feel anonymous. Each prisoner had to be called only by his ID number and could only refer to himself and the other prisoners by number. Their clothes comprised a smock with their number written on it, but no underclothes. They also had a tight nylon cap to cover their hair, and a locked chain around one ankle. All guards were dressed in identical uniforms of khaki, and they carried a whistle around their neck and a billy club borrowed from the police. Guards also wore special sunglasses, to make eye contact with prisoners impossible. Three guards worked shifts of eight hours each (the other guards remained on call). Guards were instructed to do whatever they thought was necessary to maintain law and order in the prison and to command the respect of the prisoners. No physical violence was permitted. Zimbardo observed the behavior of the prisoners and guards (as a researcher), and also acted as a prison warden.

Within a very short time both guards and prisoners were settling into their new roles, with the guards adopting theirs quickly and easily.

Asserting Authority

Within hours of beginning the experiment some guards began to harass prisoners. At 2:30 A.M. prisoners were awakened from sleep by blasting whistles for the first of many "counts". The counts served as a way to familiarizing the prisoners with their numbers. More importantly, they provided a regular occasion for the guards to exercise control over the prisoners. The prisoners soon adopted prisoner-like behavior too. They talked about prison issues a great deal of the time. They 'told tales' on each other to the guards. They started taking the prison rules very seriously, as though they were there for the prisoners' benefit and infringement would spell disaster for all of them. Some even began siding with the guards against prisoners who did not obey the rules.

Physical Punishment

The prisoners were taunted with insults and petty orders, they were given pointless and boring tasks to accomplish, and they were generally dehumanized. Push-ups were a common form of physical punishment imposed by the guards. One of the guards stepped on the prisoners' backs while they did push-ups, or made other prisoners sit on the backs of fellow prisoners doing their push-ups.

Asserting Independence

Because the first day passed without incident, the guards were surprised and totally unprepared for the rebellion which broke out on the morning of the second day. During the second day of the experiment, the prisoners removed their stocking caps, ripped off their numbers, and barricaded themselves inside the cells by putting their beds against the door. The guards called in reinforcements. The three guards who were waiting on stand-by duty came in and the night shift guards voluntarily remained on duty.

Putting Down the Rebellion

The guards retaliated by using a fire extinguisher which shot a stream of skin-chilling carbon dioxide, and they forced the prisoners away from the doors. Next, the guards broke into each cell, stripped the prisoners naked and took the beds out. The ringleaders of the prisoner rebellion were placed into solitary confinement. After this, the guards generally began to harass and intimidate the prisoners.

Special Privileges

One of the three cells was designated as a "privilege cell". The three prisoners least involved in the rebellion were given special privileges. The guards gave them back their uniforms and beds and allowed them to wash their hair and brush their teeth. Privileged prisoners also got to eat special food in the presence of the other prisoners who had temporarily lost the privilege of eating. The effect was to break the solidarity among prisoners.

Consequences of the Rebellion

Over the next few days, the relationships between the guards and the prisoners changed, with a change in one leading to a change in the other. Remember that the guards were firmly in control and the prisoners were totally dependent on them. As the prisoners became more dependent, the guards became more derisive towards them. They held the prisoners in contempt and let the prisoners know it. As the guards' contempt for them grew, the prisoners became more submissive. As the prisoners became more submissive, the guards became more aggressive and assertive. They demanded ever greater obedience from the prisoners. The prisoners were dependent on the guards for everything so tried to find ways to please the guards, such as telling tales on fellow prisoners.

Prisoner #8612

Less than 36 hours into the experiment, Prisoner #8612 began suffering from acute emotional disturbance, disorganized thinking, uncontrollable crying, and rage. After a meeting with the guards where they told him he was weak, but offered him "informant" status, #8612 returned to the other prisoners and said "You can't leave. You can't quit". Soon #8612 "began to act 'crazy,' to scream, to curse, to go into a rage that seemed out of control". It wasn't until this point that the psychologists realized they had to let him out.

A Visit from Parents

The next day, the guards held a visiting hour for parents and friends. They were worried that when the parents saw the state of the jail, they might insist on taking their sons home. Guards washed the prisoners, had them clean and polish their cells, fed them a big dinner and played music on the intercom. After the visit, rumor spread of a mass escape plan. Afraid that they would lose the prisoners, the guards and experimenters tried to enlist the help and facilities of the Palo Alto police department. The guards again escalated the level of harassment, forcing them to do menial, repetitive work such as cleaning toilets with their bare hands.

Catholic Priest

Zimbardo invited a Catholic priest who had been a prison chaplain to evaluate how realistic our prison situation was. Half of the prisoners introduced themselves by their number rather than name. The chaplain interviewed each prisoner individually. The priest told them the only way they would get out was with the help of a lawyer.

Prisoner #819

Eventually while talking to the priest, #819 broke down and began to cry hysterically, just two previously released prisoners had. The psychologists removed the chain from his foot, the cap off his head, and told him to go and rest in a room that was adjacent to the prison yard. They told him they would get him some food and then take him to see a doctor. While this was going on, one of the guards lined up the other prisoners and had them chant aloud: "Prisoner #819 is a bad prisoner. Because of what Prisoner #819 did, my cell is a mess, Mr. Correctional Officer". The psychologists realized #819 could hear the chanting and went back into the room where they found him sobbing uncontrollably. The psychologists tried to get him to agree to leave the experiment, but he said he could not leave because the others had labeled him a bad prisoner.

Back to Reality

At that point, Zimbardo said, "Listen, you are not #819. You are [his name], and my name is Dr. Zimbardo. I am a psychologist, not a prison superintendent, and this is not a real prison. This is just an experiment, and those are students, not prisoners, just like you. Let's go". He stopped crying suddenly, looked up and replied, "Okay, let's go," as if nothing had been wrong.

An End to the Experiment

Zimbardo (1973) had intended that the experiment should run for two weeks, but on the sixth day it was terminated, due to the emotional breakdowns of prisoners, and excessive aggression of the guards. Christina Maslach, a recent Stanford Ph.D. brought in to conduct interviews with the guards and prisoners, strongly objected when she saw the prisoners being abused by the guards. Filled with outrage, she said, "It's terrible what you are doing to these boys!" Out of 50 or more outsiders who had seen our prison, she was the only one who ever questioned its morality.

Zimbardo (2008) later noted, "It wasn't until much later that I realized how far into my prison role I was at that point -- that I was thinking like a prison superintendent rather than a research psychologist".

According to Zimbardo and his colleagues, the Stanford Prison Experiment revealed how people will readily conform to the social roles they are expected to play, especially if the roles are as strongly stereotyped as those of the prison guards. Because the guards were placed in a position of authority, they began to act in ways they would not usually behave in their normal lives. The "prison" environment was an important factor in creating the guards' brutal behavior (none of the participants who acted as guards showed sadistic tendencies before the study). Therefore, the findings support the situational explanation of behavior rather than the dispositional one. Zimbardo proposed that two processes can explain the prisoner's 'final submission'. Deindividuation may explain the behavior of the participants; especially the guards. This is a state when you become so immersed in the norms of the group that you lose your sense of identity and personal responsibility. The guards may have been so sadistic because they did not feel what happened was down to them personally – it was a group norm. The also may have lost their sense of personal identity because of the uniform they wore. Also, learned helplessness could explain the prisoner's submission to the guards. The prisoners learned that whatever they did had little effect on what happened to them. In the mock prison the unpredictable decisions of the guards led the prisoners to give up responding. After the prison experiment was terminated, Zimbardo interviewed the participants. Here's an excerpt:    'Most of the participants said they had felt involved and committed. The research had felt "real" to them. One guard said, "I was surprised at myself. I made them call each other names and clean the toilets out with their bare hands. I practically considered the prisoners cattle and I kept thinking I had to watch out for them in case they tried something".     Another guard said "Acting authoritatively can be fun. Power can be a great pleasure". And another: "... during the inspection I went to Cell Two to mess up a bed which a prisoner had just made and he grabbed me, screaming that he had just made it and that he was not going to let me mess it up. He grabbed me by the throat and although he was laughing I was pretty scared. I lashed out with my stick and hit him on the chin although not very hard, and when I freed myself I became angry"'. Most of the guards found it difficult to believe that they had behaved in the brutalizing ways that they had. Many said they hadn't known this side of them existed or that they were capable of such things. The prisoners, too, couldn't believe that they had responded in the submissive, cowering, dependent way they had. Several claimed to be assertive types normally. When asked about the guards, they described the usual three stereotypes that can be found in any prison: some guards were good, some were tough but fair, and some were cruel.

Critical Evaluation

Demand characteristics could explain the findings of the study. Most of the guards later claimed they were simply acting. Because the guards and prisoners were playing a role, their behavior may not be influenced by the same factors which affect behavior in real life. This means the study's findings cannot be reasonably generalized to real life, such as prison settings. I.e, the study has low ecological validity. However, there is considerable evidence that the participants did react to the situation as though it was real. For example, 90% of the prisoners' private conversations, which were monitored by the researchers, were on the prison conditions, and only 10% of the time were their conversations about life outside of the prison. The guards, too, rarely exchanged personal information during their relaxation breaks - they either talked about 'problem prisoners,' other prison topics, or did not talk at all. The guards were always on time and even worked overtime for no extra pay. When the prisoners were introduced to a priest, they referred to themselves by their prison number, rather than their first name. Some even asked him to get a lawyer to help get them out. The study may also lack population validity as the sample comprised US male students. The study's findings cannot be applied to female prisons or those from other countries. For example, America is an individualist culture (were people are generally less conforming) and the results may be different in collectivist cultures (such as Asian countries). A strength of the study is that it has altered the way US prisons are run. For example, juveniles accused of federal crimes are no longer housed before trial with adult prisoners (due to the risk of violence against them). Another strength of the study is that the harmful treatment of participant led to the formal recognition of ethical guidelines by the American Psychological Association. Studies must now undergo an extensive review by an institutional review board (US) or ethics committee (UK) before they are implemented. A review of research plans by a panel is required by most institutions such as universities, hospitals, and government agencies. These boards review whether the potential benefits of the research are justifiable in the light of the possible risk of physical or psychological harm. These boards may request researchers make changes to the study's design or procedure, or in extreme cases deny approval of the study altogether.

Ethical Issues

The study has received many ethical criticisms, including lack of fully informed consent by participants as Zimbardo himself did not know what would happen in the experiment (it was unpredictable). Also, the prisoners did not consent to being 'arrested' at home. The prisoners were not told partly because final approval from the police wasn't given until minutes before the participants decided to participate, and partly because the researchers wanted the arrests to come as a surprise. However, this was a breach of the ethics of Zimbardo's own contract that all of the participants had signed. Participants playing the role of prisoners were not protected from psychological harm, experiencing incidents of humiliation and distress. For example, one prisoner had to be released after 36 hours because of uncontrollable bursts of screaming, crying and anger. However, in Zimbardo's defense, the emotional distress experienced by the prisoners could not have been predicted from the outset. Approval for the study was given by the Office of Naval Research, the Psychology Department and the University Committee of Human Experimentation. This Committee also did not anticipate the prisoners' extreme reactions that were to follow. Alternative methodologies were looked at which would cause less distress to the participants but at the same time give the desired information, but nothing suitable could be found. Extensive group and individual debriefing sessions were held, and all participants returned post-experimental questionnaires several weeks, then several months later, then at yearly intervals. Zimbardo concluded there were no lasting negative effects. Zimbardo also strongly argues that the benefits gained about our understanding of human behavior and how we can improve society should out balance the distress caused by the study. However, it has been suggested that the US Navy was not so much interested in making prisons more human and were, in fact, more interested in using the study to train people in the armed services to cope with the stresses of captivity.

Discussion Questions

1. What are the effects of living in an environment with no clocks, no view of the outside world, and minimal sensory stimulation? 2. Consider the psychological consequences of stripping, delousing, and shaving the heads of prisoners or members of the military. What transformations take place when people go through an experience like this? 3. The prisoners could have left at any time, and yet, they didn't. Why? 4. After the study, how do you think the prisoners and guards felt? 5. If you were the experimenter in charge, would you have done this study? Would you have terminated it earlier? Would you have conducted a follow-up study?

A Theater of Inquiry and Evil

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The guard, eyes hidden behind mirrored sunglasses, scanned the lineup of inmates along the corridor wall, stopping on prisoner No. 416.

“Why don’t you play Frankenstein,” he said. It was a command, not a suggestion.

“2093,” he drawled, turning to another prisoner as a video camera captured every move. “You can be the bride of Frankenstein. You stand over here.”

The inmates wore stocking caps, flip-flops and smocks without underwear. It was the uniform they had been issued the day they were rounded up, stripped naked and locked in the dark basement, three to a cell.

The prisoners knew this guard as the most oppressive. They called him John Wayne.

He was 18, stood 6 feet 2, had long sideburns and worked the evening shift. A whistle dangled from his neck as he paced the halls.

“I want you to walk over here like Frankenstein and say that you love 2093,” he calmly told 416.

Body swaying, knees locked, arms outstretched, 416 plodded toward his bride.

“I love you, 2093,” he said.

“Get up close!” another guard barked. “Get up close!”

John Wayne shoved the prisoners together into an embrace.

“I love you, 2093,” the prisoner repeated.

In the basement of the psychology building at Stanford University, Philip Zimbardo, a young professor in the department, watched John Wayne with growing interest.

It was August 1971, and the professor’s experiment was spinning into the stuff of social scientist dreams. Clues to the nature of evil seemed to be unfolding before him.

With money left over from an Office of Naval Research grant to study antisocial behavior, he had set up a mock prison and recruited young men to serve as prisoners and guards. The professor convinced the Navy that the study might help improve conditions in its prisons.

Past attempts to explain prison brutality had focused largely on personality. Prisoners were social misfits; guards were sometimes unstable themselves and prone to violence.

Zimbardo wondered if there was something inherent in the social structure of prison -- powerful guards and powerless inmates -- that could make ordinary people do evil things.

The experiment was to last two weeks.

Three decades later, the Stanford Prison Experiment stands as one of the seminal studies on the psychology of evil.

It is mentioned in nearly every introductory psychology and sociology textbook. “Quiet Rage,” the documentary Zimbardo made about the experiment, is shown in classes across the country.

The work made Zimbardo a psychology star. His study has been frequently paired with another classic experiment on human cruelty conducted by Stanley Milgram at Yale University in the 1960s. That experiment, in which subjects delivered what they believed were increasingly powerful electric shocks to people seated across a barrier, showed a human tendency to obey authority figures, even if it meant inflicting great pain on others.

When the photos of grinning U.S. soldiers, posing with stacks of naked Iraqi inmates at Abu Ghraib prison near Baghdad, recently flashed across television screens, the lessons of the Stanford Prison Experiment were revived once again.

Zimbardo has given dozens of interviews comparing Abu Ghraib to the prison in his experiment: the lack of training of the guards, the gradual escalation of abuse, the lack of accountability.

“There are so many eerie parallels,” said Zimbardo, now semiretired from Stanford.

Or are there?

Just ask the guards and prisoners three decades later.

Dave Eshleman, now a successful mortgage broker in Saratoga, has lived all these years with the maddening ghost of John Wayne.

He’s not the type to hold a grudge, but he is annoyed that Zimbardo has propagated the idea that his transformation into the sadistic guard John Wayne happened naturally.

“This is not the kind of person I am,” he said.

Douglas Korpi, who was a prisoner in the experiment and later became a prison psychologist, long ago severed all contact with Zimbardo, disgusted with the experiment and the professor’s promotion of it.

“That clever Zimbardo,” Korpi said. “He manages to be everywhere somehow.”

Like most things in life, the truth of those few days in 1971 is a matter of interpretation.

It started with an ad in the Palo Alto Times: “Male college students needed for psychological study of prison life.”

The pay: $15 a day.

Zimbardo screened more than 70 applicants to make sure they were stable. The final group of 18 -- plus several alternates -- was randomly split into prisoners and guards.

The day before the prisoners arrived, Zimbardo convened the guards and told them their job was to maintain order without using violence.

“You can create a sense of fear in them to some degree,” he said. “We’re going to take away their individuality in various ways. In general, what this all leads to is a sense of powerlessness. We have total power in this situation and they have none.”

Instructed to create the prison rules, the guards came up with 17. Each guard would be addressed as “Mr. Correctional Officer.” Prisoners would call each other by the numbers sewn on their uniforms. No talking during meals. No references to an experiment.

Zimbardo would play the superintendent.

It wasn’t long before the first signs of strain appeared. On Day 2, Korpi, prisoner No. 8612, was already pleading to leave.

He and his cellmate, No. 1037, ripped the numbers off their smocks and used their beds to barricade their cell shut. The guards sprayed a fire extinguisher through the bars and pushed open the door. They chained the two prisoners together and made them stagger down the hall naked.

By the evening, 8612 seemed to be losing control. John Wayne ordered him into “the hole,” a tiny closet used for solitary confinement.

After being returned to his cell, 8612 began to cry out: “I got to go ... to a doctor ... anything ... I can’t stay in here ... I want out!” His voice rose to a scream. “And I want out now!”

“I mean, God. I mean, Jesus Christ! I’m burning up inside, don’t you know.”

Zimbardo reluctantly let 8612 leave. The other inmates were told that he had been sent to a maximum-security unit.

It was only the beginning.

After a 10-minute prison visit on Day 3, a mother wrote to Zimbardo complaining that her “haggard” inmate son had “not seen the sun for so long.”

“I had not expected anything quite so severe,” she wrote, signing the letter, “Mother of 1037.”

The prisoners were forced to clean toilets with their bare hands, pluck thorns out of blankets that had been dragged through the bushes and defecate in buckets that remained in their cells overnight.

John Wayne grew more perverse, forcing some prisoners to play leapfrog, which caused their smocks to ride up, exposing their genitals.

Once John Wayne asked two inmates to simulate sodomy, although he gave up when they refused. The other guards said nothing.

Before each eight-hour shift, John Wayne stood before a bathroom mirror, smacking a nightstick into his palm. “Son of a bitch, I’m going to get you today,” he muttered, preparing to stride into the cellblock.

His abuse increased even as the inmates stopped resisting. More began to crumble. A few wept. One prisoner, berated at a “parole hearing,” broke out in a rash and was sent home.

From behind a black wall at the end of the cellblock, Zimbardo’s graduate students were videotaping the experiment.

“Do you see that?” Zimbardo asked a young visitor. “Come on, look -- it’s amazing stuff.”

A line of inmates, chained together with bags over their heads, marched down the hall, on a circuitous route to the bathroom. John Wayne was cursing out the inmates.

The visitor was Christina Maslach, who had just earned her doctorate under Zimbardo and was dating him.

She had heard about John Wayne, and was horrified to learn that he was the nice young man she had just met in the guards’ break room.

There he was, the same person she had found so pleasant. He now spoke with a Southern accent. He even seemed to move differently.

Unsettled, Maslach tried to ignore Zimbardo’s pleas to watch the drama -- and the way he seemed to enjoy the dehumanization of the prisoners.

“I already saw it!” she shot back.

Maslach, who had just been hired as an assistant professor at UC Berkeley, suddenly felt she no longer knew Zimbardo.

“I think it’s terrible what you are doing to those boys,” she told him.

Zimbardo, absorbed in his role as superintendent, initially defended the study. But the next day -- Day 6 -- the professor called off the experiment.

That might have been the end of the Stanford Prison Experiment, but the next day three inmates and three guards at San Quentin State Prison were killed during a revolt and escape attempt. Three weeks later, more than 40 people died at Attica Correctional Facility in upstate New York in a four-day riot over inhumane treatment.

In October 1971, Zimbardo described his study at a congressional hearing: The enormous power of control given to guards can ignite the darker side of human nature.

In the ensuing years, the professor appeared on Phil Donahue’s show “That’s Incredible” and “60 Minutes.” There was a failed deal for a movie starring Leonardo DiCaprio. And there was a German film, “Das Experiment,” which began like the Stanford study but quickly turned into a massacre.

But was the corrupting power of prison actually revealed by those college students?

Eshleman, now 51 and 30 pounds heavier than in his John Wayne days, chuckled slightly.

“I was doing a role,” he explained in his office. “Anybody that knows me, if they had seen me do this shtick, they would have just laughed at me.”

He explained that he had been acting to help Zimbardo get results. That first night on the job, as he watched the prisoners through the bars, he was struck that everybody was treating the study like summer camp.

“I was going to make something happen in this experiment,” he recalled. “That would be a good thing because it would help show the evils inherent in a prison-type environment.”

He had played the lead in high school musicals and knew something about acting. He tried to imagine the “worst S.O.B. guard” he could, settling on the prison captain in the 1967 movie “Cool Hand Luke.”

He got ideas for abuse from the hazing upperclassmen had inflicted on him the previous year when he rushed Lambda Phi Alpha at Chapman College in Orange.

“If I wasn’t pushing the envelope, would we still be talking about this experiment?” he said. “I don’t know.”

Some academics have criticized the study, arguing that the prisoners and guards were simply trying to fulfill Zimbardo’s expectations.

One of the experiment’s most famous abuses -- the placing of bags over the prisoners’ heads -- was an idea hatched by the professor and his team so the illusion of prison would not be broken when inmates were taken to the bathroom outside the “prison” compound.

And it was Carlo Prescott, an ex-convict who had helped inspire the experiment and worked as its chief consultant, who had viciously lambasted one inmate at his mock parole hearing and triggered the much-cited psychosomatic rash.

Korpi, the crazed star of the prison video, says his role has been distorted by Zimbardo.

Korpi said the cruelty of some guards was real: “When you see it in their eyes, it doesn’t matter if they say they were just acting. They were into it.”

But he said he staged the distress of prisoner 8612.

He had just graduated from UC Berkeley and was furious when guards refused to call his girlfriend to deliver the books he needed to study for the graduate school entrance exam.

His screaming was all part of a plan to convince the researchers that he had lost control. They would have to release him.

“If a clinician had seen what I did -- it was obvious, “ said Korpi, now 55. “Zimbardo thought I was losing it.”

The professor has heard all the criticisms before.

“What’s really difficult is to separate out people’s justification after the fact from what they were really thinking, feeling, doing during the time,” he said.

Zimbardo said acting was in fact the first step toward becoming a “John Wayne.” By living the part eight hours a day, Eshleman had begun “internalizing his character,” the professor said. “He’s becoming that person.”

In a sense, evil is theater.

The actors in the Stanford experiment have continued to vie for control of the stage long after the performance ended.

In an interview in the 1980s for Zimbardo’s documentary, Korpi did not downplay his apparent freakout.

“I’ve never screamed so much in my life. I’ve never been so upset in my life,” he said in the video. “It was an experience of being out of control -- both of the situation and of my feelings.”

“Maybe I have always had difficulty with the notion of losing control. I wanted to understand myself, so I went into psychology.”

Korpi gave that interview only after Zimbardo agreed to scale back the hysteria scene in the documentary.

“He’s embarrassed that he became like a little kid -- that he cried,” Zimbardo said.

Korpi won’t talk to Zimbardo anymore.

“This guy is an entertainer,” Korpi said dismissively.

Zimbardo has, in fact, seemed to be everywhere lately.

Since the Abu Ghraib scandal broke in late April, his prison experiment website, www.prison-exp.org, has gotten 1 million unique hits a week. He has appeared in news articles, on the radio and on television.

“From Bush on down, we’re saying that it’s a few bad apples, it’s isolated,” he said on CNN in late May. “But what’s bad is the barrel.... It’s the barrel of the evil of prisons.”

Married to Maslach, 71-year-old Zimbardo is now working on a book about the study. An official at Maverick Films, the production company co-owned by Madonna, said they were close to sealing a deal for a new script based on the prison experiment.

The U.S. Army has started to use Zimbardo’s documentary to train its prison guards in Iraq.

The images from Abu Ghraib stunned Eshleman, as they did most people.

“They were digging it,” he said of the soldiers. “They were getting off on it.”

But thinking back to his days as a guard, he could understand how the abuse could have escalated.

“As an 18-year-old, you’re so enamored with what you’re maybe getting away with that you just keep pushing it. You want to see where the limits are. How far can you take this thing?”

He never got the chance to find out with John Wayne because the experiment was cut short. “It’s not my favorite role, but it will probably be my most famous,” he said.

He still acts on the side. Last month, at a private retreat in Portola Valley, he appeared in the play “Honeymooners in Vegas,” as a lounge singer.

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Here's Why We Need To Rethink Everything We Know About The Stanford Prison Experiment

This could have huge implications for social psychology.

BuzzFeed Staff

The Stanford Prison Experiment is arguably one of the most famous experiments in modern psychology and has been used as a demonstration of how people rapidly conform to their roles in extraordinary circumstances and perform acts that would be branded as "evil" in average contexts.

The experiment has become part of the fabric of modern psychology and has been taught routinely to first-year psychology students around the world, making an appearance in the great majority of social psychology textbooks.

However, its legitimacy is now being openly debated by a panel of international psychology experts including professor Philip Zimbardo, the researcher from Stanford University who designed and conducted the experiment.

So, what was the Stanford Prison Experiment?

The experiment was part of a trend in modern psychology to understand the emergence of violent and immoral human behaviour in different contexts in the wake of World War II and the Holocaust.

The experiment took place in the summer of 1971 using 24 male college student volunteers.

"Stanford County Prison" was created by boarding up and building cells in a section of the basement in the psychology department of Stanford University.

The participants were randomly assigned to one of two groups — guards or prisoners.

The prisoners were referred to by ID numbers rather than their names by the guards and fellow prisoners.

Still from the 2001 BBC Prison Study.

Zimbardo and his co-authors wrote a paper on the study, which began: "What happens when you put good people in an evil place? Does humanity win over evil, or does evil triumph? These are some of the questions we posed in this dramatic simulation of prison life".

The study began by "arresting" the prisoners and taking them from their homes in a police car. The prisoners were then searched, stripped naked and deloused with a spray.

Over the course of six days at the Stanford County Prison psychological and physical abuse was committed by the guards against the prisoners.

The study was intended to span a fortnight but was cut off early by legal complaints and the objections of a PhD student who was brought in to interview the participants.

The guards inflicted punishments such as menial tasks, exercising (jumping jacks and push-ups), solitary confinement, sleep deprivation and cleaning toilets with their bare hands.

One of the prisoners (#8612), Douglas Korpi, a 22-year-old Berkeley graduate, began to exhibit uncontrollable crying and rage 36 hours into the experiment, described by Zimbardo as "acute emotional disturbance".

Korpi told other prisoners "you can't leave, you can't quit" and he was removed early from the prison experiment due to his psychological distress.

Another prisoner (#819) was exhibiting psychological distress and continuous crying. Zimbardo recounts his release in his official report of the study:

"I suggested we leave, but he refused. Through his tears, he said he could not leave because the others had labelled him a bad prisoner. Even though he was feeling sick, he wanted to go back and prove he was not a bad prisoner. At that point I said, 'Listen, you are not #819. You are [his name], and my name is Dr Zimbardo. I am a psychologist, not a prison superintendent, and this is not a real prison. This is just an experiment, and those are students, not prisoners, just like you. Let's go.' He stopped crying suddenly, looked up at me like a small child awakened from a nightmare, and replied, 'Okay, let's go'."

The guards, who all wore opaque aviators (inspired by the movie Cool Hand Luke ) were allegedly given no specific training on how to be guards in the official accounts of the study.

One guard, who was renowned for taking his role particularly seriously and acting with cruelty, was dubbed "John Wayne" by the prisoners.

Zimbardo reflected:

"Where had our 'John Wayne' learned to become such a guard? How could he and others move so readily into that role? How could intelligent, mentally healthy, 'ordinary' men become perpetrators of evil so quickly? These were questions we were forced to ask."

The Stanford Prison Experiment has since been used in psychology as a demonstration of how humans can behave aggressively and abuse power and exhibit "evil" within certain authority contexts.

But now the experiment and the legitimacy of its results are being called into question.

In a consensus statement released this week, professors Craig Haney and Zimbardo from the Stanford Prison Experiment, as well as professors Alex Haslam and Stephen Reicher who conducted the BBC Prison Study , have called for a constructive debate on the findings and legacy of the experiment.

The BBC Prison Study was an experiment undertaken by Haslam and Reicher and broadcast in 2002.

The study was similar to the Stanford Prison Experiment and took place over nine days with five guards and 10 prisoners.

However, there was a profound difference from the results of Zimbardo's experiment in the power balance between the prisoners and guards.

In the BBC study it was found that the prisoners banded together and acted against the prison guards, challenging their authority and driving some distressed guards to leave the experiment.

Haslam and Reicher concluded: "People do not conform blindly to roles; they only internalise roles when they identify with the groups that create them."

The results of the BBC study, as well as decades of social psychology research, appear to contradict evidence from the Stanford Prison Experiment that it is context alone that leads people to abuse power or act sadistically.

The controversy begins with some perceived flaws in Zimbardo's experimental design.

Firstly, the digitisation of the footage and audio recordings from the Stanford Prison Experiment archive contradicted Zimbardo's claim that the prison guard's brutal treatment of the prisoners was a "natural" consequence of their assigned role.

In 2016, social science researcher Thibault Le Texier published Histoire d'un Mensonge (Story of a Lie), a book investigating inconsistencies in Zimbardo's original reports.

New evidence outlined in Le Texier's book suggested Zimbardo and the experimenters had, in fact, encouraged particular behaviours from the guards.

One audio recording of a meeting with an assigned prison guard involves Zimbardo's prison warden and researcher David Jaffe telling the guard that they "really want to get you active and involved because the guards have to know that every guard is going to be what we call a tough guard".

"You have to try and get it in you ... you have to be firm and you have to be in the action and that sort of thing," said Jaffe. "It's really important for the workings of the experiment."

Audio recordings such as these, as well as the transcript of the orientation of the Stanford County Prison guards, suggest that the participants were coached to act in a certain way, rather than exhibiting a natural abuse of powers.

Zimbardo himself told the guards in an orientation session:

"You can create in the prisoners feelings of boredom, a sense of fear to some degree, you can create a notion of arbitrariness that their life is totally controlled by us, by the system, you, me … They can do nothing, say nothing, that we don't permit…"

Zimbardo has denied that these sort of statements could have such extreme implications for the way the guards behaved in Stanford County Prison.

In an interview with Vox's Brian Resnick, Zimbardo stated:

"The point is telling a guard to be tough does not mean telling a guard to be mean, to be cruel, to be sadistic, which many of the guards became of their own volition playing the role of what they thought was a prison guard. So I reject your assumption entirely."

Haslam, who has been studying the dynamics of social interactions such as these for decades and has formed theories that contradict Zimbardo's, told BuzzFeed News that the discovery of these recordings was like the "Rosetta Stone" for him and research partner Reicher.

Haslam's theory is that extraordinary accounts of extreme cruelty and dehumanisation that have occurred throughout history, such as the Holocaust and the Rwandan Genocide of 1994, rest upon nuances of leadership.

"Part of his [Zimbardo's] theoretical analysis is that if you put people in a toxic context, they will become toxic essentially on their own and that's really not what happens."

Haslam states that the recordings and transcripts are a "really important part of the study and it makes what happened in the Stanford Prison Experiment more relevant to us and more interesting to us in many ways".

Haslam stresses that in order to persuade people to act aggressively towards an out-group, they must be convinced that they have a common link and common grounds for motivation to act in that manner.

Haslam notes that in Jaffe's orientation session as prison warden, he used the term "we" approximately 50 times — a factor that contributes to the guards perceiving themselves as a united force against a common enemy.

In a 2007 paper Dr Thomas Carnahan and Dr Sam McFarland also put forward the idea that the results of the Stanford Prison Experiment were misleading because Zimbardo advertised for volunteers in the newspaper.

Carnahan and McFarland note that the sort of personalities who put their names forward for such an experiment from newspaper advertisements were rated highly on "Machiavellianism, narcissism and social dominance, and lower on empathy and altruism".

The treatment of the prisoners, as well as the legitimacy of their reactions, has also come into question.

According to an investigation by author Ben Blum, who wrote a piece deconstructing the Stanford Prison Experiment titled The Lifespan Of A Lie, Korpi (Prisoner #8612) denies that his psychological breakdown was legitimate.

Korpi told Blum: "Anybody who is a clinician would know that I was faking ... If you listen to the tape, it's not subtle. I'm not that good at acting."

Korpi and fellow prisoner Richard Yacco reported that they were simply shocked that the experimenters would not let them leave Stanford County Prison when requested to exit the study.

However, Zimbardo denies this claim in the interview with Resnick, saying he believes Korpi made his statement in retrospect because he is "ashamed of having broken down".

So, what do other studies say?

In 1979, professor Sydney Lovibond from the University of New South Wales (UNSW) conducted a study that looked at the effects of three different types of "prison" regimes, including one based on a normal medium-security prison, and two that allowed prisoners to participate and exhibit individuality.

The study observed some of the same behaviours of exertion of authority by the guards over the prisoners, including the following interaction:

Officer: Get your head in. Prisoner: Why? Officer: Because I'm an officer and you're a prisoner and I'm telling you — that's why! Prisoner: It's an open window and I've got a right to look out. Officer: In a real prison there wouldn't be an open window, and as such you wouldn't have the right to look out. Now get your head in! Prisoner: Well, it isn't a real prison is it, and I'll look out when I want to — mate! Officer: You're on report. Prisoner: Big deal. Officer (putting his face close up to the prisoner's): You've got four more days in here sonny, four more days remember?

However, the most important difference between Lovibond's conclusion and Zimbardo's is that the UNSW study found it was the "social organisation" of a prison regime rather than the characteristics of the individuals themselves that most influenced the behaviour exhibited.

Haslam also concluded in another paper that in classic conformity studies such as Zimbardo's or Stanley Milgram's obedience and electronic shock experiment (in which participants were found to willingly submit their peers to dangerous electric shocks when told to by researchers), there is always a significant amount of resistance to the demands.

In the Milgram experiment, participants actually exhibited three types of explicit resistance to the researchers' demands.

Haslam notes that the guard who was told to act "tough" by Jaffe in the audio recording was being instructed to do so because he wasn't submitting sufficiently to acting as the guards were expected to.

He believes that this aspect of significant resistance to authority regimes has been ignored by the conformity narrative.

So, why does any of this really matter?

The implications of Zimbardo's study – that people will conform to roles and abuse authority without question – have far-reaching political consequences.

Haslam believes that Zimbardo's conclusions need to be inspected because they suggest people will always fall in line with authority, despite moral objections.

"It's also I think very politically problematic to suggest that if you put people in bad situations, they'll do bad things, because it takes away any agency and it also takes away responsibility."

Haslam hopes that an open debate with Zimbardo and Haney will lead to a more nuanced discussion about personal responsibilities in the face of authoritarian regimes or bodies of power.

"The point is, in history tyranny has always been overthrown because ultimately people push back against it and say, 'This is not right'".

* BuzzFeed News has sought comment from Professor Philip Zimbardo.

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Stanford Prison Experiment

• Quiet Rage: The Stanford Prison Experiment

Tape E: 8612

Bibliography.