zimbardo experiment conclusion

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.

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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

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The Stanford Prison Experiment

Participants
Setting and Procedure

In August of 1971, psychologist Philip Zimbardo and his colleagues created an experiment to determine the impacts of being a prisoner or prison guard. The Stanford Prison Experiment, also known as the Zimbardo Prison Experiment, went on to become one of the best-known studies in psychology's history —and one of the most controversial.

This study has long been a staple in textbooks, articles, psychology classes, and even movies. Learn what it entailed, what was learned, and the criticisms that have called the experiment's scientific merits and value into question.

Purpose of the Stanford Prison Experiment

Zimbardo was a former classmate of the psychologist Stanley Milgram . Milgram is best known for his famous obedience experiment , and Zimbardo was interested in expanding upon Milgram's research. He wanted to further investigate the impact of situational variables on human behavior.

Specifically, the researchers wanted to know how participants would react when placed in a simulated prison environment. They wondered if physically and psychologically healthy people who knew they were participating in an experiment would change their behavior in a prison-like setting.

Participants in the Stanford Prison Experiment

To carry out the experiment, researchers set up a mock prison in the basement of Stanford University's psychology building. They then selected 24 undergraduate students to play the roles of both prisoners and guards.

Participants were chosen from a larger group of 70 volunteers based on having no criminal background, no psychological issues , and no significant medical conditions. Each volunteer agreed to participate in the Stanford Prison Experiment for one to two weeks in exchange for $15 a day.

Setting and Procedures

The simulated prison included three six-by-nine-foot prison cells. Each cell held three prisoners and included three cots. Other rooms across from the cells were utilized for the jail guards and warden. One tiny space was designated as the solitary confinement room, and yet another small room served as the prison yard.

The 24 volunteers were randomly assigned to either the prisoner or guard group. Prisoners were to remain in the mock prison 24 hours a day during the study. Guards were assigned to work in three-man teams for eight-hour shifts. After each shift, they were allowed to return to their homes until their next shift.

Researchers were able to observe the behavior of the prisoners and guards using hidden cameras and microphones.

Results of the Stanford Prison Experiment

So what happened in the Zimbardo experiment? While originally slated to last 14 days, it had to be stopped after just six due to what was happening to the student participants. The guards became abusive and the prisoners began to show signs of extreme stress and anxiety .

It was noted that:

While the prisoners and guards were allowed to interact in any way they wanted, the interactions were hostile or even dehumanizing.
The guards began to become aggressive and abusive toward the prisoners while the prisoners became passive and depressed.
Five of the prisoners began to experience severe negative emotions , including crying and acute anxiety, and had to be released from the study early.

Even the researchers themselves began to lose sight of the reality of the situation. Zimbardo, who acted as the prison warden, overlooked the abusive behavior of the jail guards until graduate student Christina Maslach voiced objections to the conditions in the simulated prison and the morality of continuing the experiment.

One possible explanation for the results of this experiment is the idea of deindividuation , which states that being part of a large group can make us more likely to perform behaviors we would otherwise not do on our own.

Impact of the Zimbardo Prison Experiment

The experiment became famous and was widely cited in textbooks and other publications. According to Zimbardo and his colleagues, the Stanford Prison Experiment demonstrated the powerful role that the situation can play in human behavior.

Because the guards were placed in a position of power, they began to behave in ways they would not usually act in their everyday lives or other situations. The prisoners, placed in a situation where they had no real control , became submissive and depressed.

In 2011, the Stanford Alumni Magazine featured a retrospective of the Stanford Prison Experiment in honor of the experiment’s 40th anniversary. The article contained interviews with several people involved, including Zimbardo and other researchers as well as some of the participants.

In the interviews, Richard Yacco, one of the prisoners in the experiment, suggested that the experiment demonstrated the power that societal roles and expectations can play in a person's behavior.

In 2015, the experiment became the topic of a feature film titled The Stanford Prison Experiment that dramatized the events of the 1971 study.

Criticisms of the Stanford Prison Experiment

In the years since the experiment was conducted, there have been a number of critiques of the study. Some of these include:

Ethical Issues

The Stanford Prison Experiment is frequently cited as an example of unethical research. It could not be replicated by researchers today because it fails to meet the standards established by numerous ethical codes, including the Code of Ethics of the American Psychological Association .

Why was Zimbardo's experiment unethical?

Zimbardo's experiment was unethical due to a lack of fully informed consent, abuse of participants, and lack of appropriate debriefings. More recent findings suggest there were other significant ethical issues that compromise the experiment's scientific standing, including the fact that experimenters may have encouraged abusive behaviors.

Lack of Generalizability

Other critics suggest that the study lacks generalizability due to a variety of factors. The unrepresentative sample of participants (mostly white and middle-class males) makes it difficult to apply the results to a wider population.

Lack of Realism

The Zimbardo Prison Experiment is also criticized for its lack of ecological validity. Ecological validity refers to the degree of realism with which a simulated experimental setup matches the real-world situation it seeks to emulate.

While the researchers did their best to recreate a prison setting, it is simply not possible to perfectly mimic all the environmental and situational variables of prison life. Because there may have been factors related to the setting and situation that influenced how the participants behaved, it may not truly represent what might happen outside of the lab.

Recent Criticisms

More recent examination of the experiment's archives and interviews with participants have revealed major issues with the research method , design, and procedures used. Together, these call the study's validity, value, and even authenticity into question.

These reports, including examinations of the study's records and new interviews with participants, have also cast doubt on some of its key findings and assumptions.

Among the issues described:

One participant suggested that he faked a breakdown so he could leave the experiment because he was worried about failing his classes.
Other participants also reported altering their behavior in a way designed to "help" the experiment .
Evidence suggests that the experimenters encouraged the guards' behavior and played a role in fostering the abusive actions of the guards.

In 2019, the journal American Psychologist published an article debunking the famed experiment. It detailed the study's lack of scientific merit and concluded that the Stanford Prison Experiment was "an incredibly flawed study that should have died an early death."

In a statement posted on the experiment's official website, Zimbardo maintains that these criticisms do not undermine the main conclusion of the study—that situational forces can alter individual actions both in positive and negative ways.

The Stanford Prison Experiment is well known both inside and outside the field of psychology . While the study has long been criticized for many reasons, more recent criticisms of the study's procedures shine a brighter light on the experiment's scientific shortcomings.

Stanford University. About the Stanford Prison Experiment .

Stanford Prison Experiment. 2. Setting up .

Sommers T. An interview with Philip Zimbardo . The Believer.

Ratnesar R. The menace within . Stanford Magazine.

Jabbar A, Muazzam A, Sadaqat S. An unveiling the ethical quandaries: A critical analysis of the Stanford Prison Experiment as a mirror of Pakistani society . J Bus Manage Res . 2024;3(1):629-638.

Horn S. Landmark Stanford Prison Experiment criticized as a sham . Prison Legal News .

Bartels JM. The Stanford Prison Experiment in introductory psychology textbooks: A content analysis . Psychol Learn Teach . 2015;14(1):36-50. doi:10.1177/1475725714568007

American Psychological Association. Ecological validity .

Blum B. The lifespan of a lie . Medium .

Le Texier T. Debunking the Stanford Prison Experiment . Am Psychol . 2019;74(7):823-839. doi:10.1037/amp0000401

Stanford Prison Experiment. Philip Zimbardo's response to recent criticisms of the Stanford Prison Experiment .

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

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What the Stanford Prison Experiment Taught Us

Guards with a blindfolded prisoner, still from the Stanford Prison Experiment conducted by Phillip Zimbardo

In August of 1971, Dr. Philip G. Zimbardo of Stanford University in California conducted what is widely considered one of the most influential experiments in social psychology to date. Made into a New York Times best seller in 2007 ( The Lucifer Effect ) and a major motion picture in 2015 ( The Stanford Prison Experiment ), the Stanford Prison Experiment has integrated itself not only into the psychology community but also popular culture. The events that occurred within this experiment, though disturbing, have given many people insight into just how much a situation can affect behavior. They have also caused many to ponder the nature of evil. How disturbing was it? Well, the proposed two-week experiment was terminated after just six days, due to alarming levels of mistreatment and brutality perpetrated on student “prisoners” by fellow student “guards.”

The study aimed to test the effects of prison life on behavior and wanted to tackle the effects of situational behavior rather than just those of disposition. After placing an ad in the newspaper, Zimbardo selected 24 mentally and physically healthy undergraduate students to participate in the study. The idea was to randomly assign nine boys to be prisoners, nine to be guards, and six to be extras should they need to make any replacements. After randomly assigning the boys, the nine deemed prisoners were “arrested” and promptly brought into a makeshift Stanford County Prison, which was really just the basement of the Stanford Psychology Department building. Upon arrival, the boys’ heads were shaved, and they were subjected to a strip search as well as delousing (measures taken to dehumanize the prisoners). Each prisoner was then issued a uniform and a number to increase anonymity. The guards who were to be in charge of the prisoners were not given any formal training; they were to make up their own set of rules as to how they would govern their prison.

Over the course of six days, a shocking set of events unfolded. While day one seemed to go by without issue, on the second day there was a rebellion, causing guards to spray prisoners with a fire extinguisher in order to force them further into their cells. The guards took the prisoners’ beds and even utilized solitary confinement. They also began to use psychological tactics, attempting to break prisoner solidarity by creating a privilege cell. With each member of the experiment, including Zimbardo, falling deeper into their roles, this “prison” life quickly became a real and threatening situation for many. Thirty-six hours into the experiment, prisoner #8612 was released on account of acute emotional distress, but only after (incorrectly) telling his prison-mates that they were trapped and not allowed to leave, insisting that it was no longer an experiment. This perpetuated a lot of the fears that many of the prisoners were already experiencing, which caused prisoner #819 to be released a day later after becoming hysterical in Dr. Zimbardo’s office.

The guards got even crueler and more unusual in their punishments as time progressed, forcing prisoners to participate in sexual situations such as leap-frogging each other’s partially naked bodies. They took food privileges away and forced the prisoners to insult one another. Even the prisoners fell victim to their roles of submission. At a fake parole board hearing, each of them was asked if they would forfeit all money earned should they be allowed to leave the prison immediately. Most of them said yes, then were upset when they were not granted parole, despite the fact that they were allowed to opt out of the experiment at any time. They had fallen too far into submissive roles to remember, or even consider, their rights.

On the sixth day, Dr. Zimbardo closed the experiment due to the continuing degradation of the prisoners’ emotional and mental states. While his findings were, at times, a terrifying glimpse into the capabilities of humanity, they also advanced the understanding of the psychological community. When it came to the torture done at Abu Ghraib or the Rape of Nanjing in China, Zimbardo’s findings allowed for psychologists to understand evil behavior as a situational occurrence and not always a dispositional one.

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How the Stanford Prison Experiment Worked

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The Takeaways

Zimbardo realized that rather than a neutral scenario, he created a prison much like real prisons, where corrupt and cruel behavior didn't occur in a vacuum, but flowed from the rules and principles of the institution to the people who carried out those principles. The behavior of the guards and prisoners wasn't dictated by some inherent internal trait, but by the situation they were in. The theory that external circumstances are the primary drivers of human behavior is known as situationist theory . Zimbardo didn't form the theory, but his experiment and later writings helped popularize it.

Experimental ethics are also an issue to consider. The Stanford Human Subjects Review Committee and Zimbardo's superiors approved the experiment — another layer of authority complicit in the experiment's outcome (it's like situationist "Inception") — but experimental ethics are more rigorous today. A modern institutional review board would likely never approve such an experiment without major modifications. Zimbardo has said that he feels the initial experiment was ethical (all the participants understood what they'd signed up for and consented), but that he suffered an ethical lapse when he allowed it to continue beyond the first emotional breakdown of a prisoner [source: Stanford Prison Experiment ].

The idea that humans have an inherent tendency toward abuse of authority and submission to authority is not ruled out by the experiment, however. The Stanford Prison Experiment is closely related to another psychological experiment that's as infamous: Stanley Milgram's obedience to authority experiment . In fact, Zimbardo and Milgram were high school classmates and colleagues at Yale University. In the obedience experiment, volunteers were directed to press buttons delivering increasingly powerful, and eventually fake lethal shocks to another person at the direction of a researcher. A large percentage of volunteers went along with the researcher's demands. However, like the Stanford Prison Experiment, the ethics, methodology and conclusions of Milgram's experiment have been called into question recently . And both experiments influenced changes in the regulation and ethical guidelines of studies with human subjects [sources: Zimbardo et al. , Defiesta ].

Zimbardo's conclusion was that we are not so much inherently "evil," but that we will commit heinous acts if encouraged to do so by systems that enable or encourage them. He took his results to the U.S. House of Representatives shortly after the experiment ended, testifying before a subcommittee on prison reform. His primary argument was that given the power institutions have to dictate the behavior of the people within them, it's necessary to reform those institutions to avoid those abuses. He suggested better training and pay for guards, better protection for prisoners' human rights , and specific training programs that could include role-playing scenarios to help guards learn to deal humanely with prisoners (and weed out the most sadistic among guards) [source: House of Representatives ]. The 2003 scandal surrounding prisoner treatment at the Iraqi prison Abu Ghraib, which mirrored the actions of Zimbardo's guards in disturbing ways, suggests that the experiment is not a relic of the past but still relevant to the way people are treated in modern civilian and military prisons.

Zimbardo's testimony also reflected his belief that researchers should not remain impartial observers, but should engage in social and political ways to act on the discoveries they make and seek ways to improve the world [source: Zimbardo et al. ].

Remember that part about Zimbardo's experiment lacking a control group? In 2002, the BBC broadcasted a similar experiment, one that conformed with modern ethics and removed many of the initial biases, such as dehumanizing the prisoners and giving the guards implements of authority. In many ways it could be seen as a control group for the Stanford Prison Experiment. The outcome? The prisoners stuck together, and the guards became disorganized. Like the Stanford Prison Experiment, this one ended early, because a group of participants planned to take over the prison, and the researchers anticipated violence [source: Reicher & Haslam ].

Author's Note: How the Stanford Prison Experiment Worked

Much of the appeal of the Stanford Prison Experiment, aside from the dark, voyeuristic thrill of learning how the subjects acted, is how easily it lets you insert yourself into the narrative Zimbardo created. What kind of guard would you be? How would you react when another guard did something sadistic? How would you react as a prisoner? Would you organize your fellow prisoners, or work against them to gain favor with the guards? Or maybe you envision yourself in Zimbardo's position, pulling the strings in your scenario. How would you have changed the conditions to alter the subjects' behavior? Could you redesign the experiment to be more ethical?

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The Real Lesson of the Stanford Prison Experiment

On the morning of August 17, 1971, nine young men in the Palo Alto area received visits from local police officers. While their neighbors looked on, the men were arrested for violating Penal Codes 211 and 459 (armed robbery and burglary), searched, handcuffed, and led into the rear of a waiting police car. The cars took them to a Palo Alto police station, where the men were booked, fingerprinted, moved to a holding cell, and blindfolded. Finally, they were transported to the Stanford County Prison—also known as the Stanford University psychology department.

They were willing participants in the Stanford Prison Experiment, one of the most controversial studies in the history of social psychology. (It’s the subject of a new film of the same name—a drama, not a documentary—starring Billy Crudup, of “Almost Famous,” as the lead investigator, Philip Zimbardo. It opens July 17th.) The study subjects, middle-class college students, had answered a questionnaire about their family backgrounds, physical- and mental-health histories, and social behavior, and had been deemed “normal”; a coin flip divided them into prisoners and guards. According to the lore that’s grown up around the experiment, the guards, with little to no instruction, began humiliating and psychologically abusing the prisoners within twenty-four hours of the study’s start. The prisoners, in turn, became submissive and depersonalized, taking the abuse and saying little in protest. The behavior of all involved was so extreme that the experiment, which was meant to last two weeks, was terminated after six days.

Less than a decade earlier, the Milgram obedience study had shown that ordinary people, if encouraged by an authority figure, were willing to shock their fellow-citizens with what they believed to be painful and potentially lethal levels of electricity. To many, the Stanford experiment underscored those findings, revealing the ease with which regular people, if given too much power, could transform into ruthless oppressors. Today, more than forty-five years later, many look to the study to make sense of events like the behavior of the guards at Abu Ghraib and America’s epidemic of police brutality. The Stanford Prison Experiment is cited as evidence of the atavistic impulses that lurk within us all; it’s said to show that, with a little nudge, we could all become tyrants.

And yet the lessons of the Stanford Prison Experiment aren’t so clear-cut. From the beginning, the study has been haunted by ambiguity. Even as it suggests that ordinary people harbor ugly potentialities, it also testifies to the way our circumstances shape our behavior. Was the study about our individual fallibility, or about broken institutions? Were its findings about prisons, specifically, or about life in general? What did the Stanford Prison Experiment really show?

The appeal of the experiment has a lot to do with its apparently simple setup: prisoners, guards, a fake jail, and some ground rules. But, in reality, the Stanford County Prison was a heavily manipulated environment, and the guards and prisoners acted in ways that were largely predetermined by how their roles were presented. To understand the meaning of the experiment, you have to understand that it wasn’t a blank slate; from the start, its goal was to evoke the experience of working and living in a brutal jail.

From the first, the guards’ priorities were set by Zimbardo. In a presentation to his Stanford colleagues shortly after the study’s conclusion, he described the procedures surrounding each prisoner’s arrival: each man was stripped and searched, “deloused,” and then given a uniform—a numbered gown, which Zimbardo called a “dress,” with a heavy bolted chain near the ankle, loose-fitting rubber sandals, and a cap made from a woman’s nylon stocking. “Real male prisoners don't wear dresses,” Zimbardo explained, “but real male prisoners, we have learned, do feel humiliated, do feel emasculated, and we thought we could produce the same effects very quickly by putting men in a dress without any underclothes.” The stocking caps were in lieu of shaving the prisoner’s heads. (The guards wore khaki uniforms and were given whistles, nightsticks, and mirrored sunglasses inspired by a prison guard in the movie “Cool Hand Luke.”)

Often, the guards operated without explicit, moment-to-moment instructions. But that didn’t mean that they were fully autonomous: Zimbardo himself took part in the experiment, playing the role of the prison superintendent. (The prison’s “warden” was also a researcher.) /Occasionally, disputes between prisoner and guards got out of hand, violating an explicit injunction against physical force that both prisoners and guards had read prior to enrolling in the study. When the “superintendent” and “warden” overlooked these incidents, the message to the guards was clear: all is well; keep going as you are. The participants knew that an audience was watching, and so a lack of feedback could be read as tacit approval. And the sense of being watched may also have encouraged them to perform. Dave Eshelman, one of the guards, recalled that he “consciously created” his guard persona. “I was in all kinds of drama productions in high school and college. It was something I was very familiar with: to take on another personality before you step out on the stage,” Eshelman said. In fact, he continued, “I was kind of running my own experiment in there, by saying, ‘How far can I push these things and how much abuse will these people take before they say, ‘Knock it off?’ ”

Other, more subtle factors also shaped the experiment. It’s often said that the study participants were ordinary guys—and they were, indeed, determined to be “normal” and healthy by a battery of tests. But they were also a self-selected group who responded to a newspaper advertisement seeking volunteers for “a psychological study of prison life.” In a 2007 study, the psychologists Thomas Carnahan and Sam McFarland asked whether that wording itself may have stacked the odds. They recreated the original ad, and then ran a separate ad omitting the phrase “prison life.” They found that the people who responded to the two ads scored differently on a set of psychological tests. Those who thought that they would be participating in a prison study had significantly higher levels of aggressiveness, authoritarianism, Machiavellianism, narcissism, and social dominance, and they scored lower on measures of empathy and altruism.

Moreover, even within that self-selected sample, behavioral patterns were far from homogeneous. Much of the study’s cachet depends on the idea that the students responded en masse, giving up their individual identities to become submissive “prisoners” and tyrannical “guards.” But, in fact, the participants responded to the prison environment in all sorts of ways. While some guard shifts were especially cruel, others remained humane. Many of the supposedly passive prisoners rebelled. Richard Yacco, a prisoner, remembered “resisting what one guard was telling me to do and being willing to go into solitary confinement. As prisoners, we developed solidarity—we realized that we could join together and do passive resistance and cause some problems.”

What emerges from these details isn’t a perfectly lucid photograph but an ambiguous watercolor. While it’s true that some guards and prisoners behaved in alarming ways, it’s also the case that their environment was designed to encourage—and, in some cases, to require—those behaviors. Zimbardo himself has always been forthcoming about the details and the nature of his prison experiment: he thoroughly explained the setup in his original study and, in an early write-up , in which the experiment was described in broad strokes only, he pointed out that only “about a third of the guards became tyrannical in their arbitrary use of power.” (That’s about four people in total.) So how did the myth of the Stanford Prison Experiment—“Lord of the Flies” in the psych lab—come to diverge so profoundly from the reality?

In part, Zimbardo’s earliest statements about the experiment are to blame. In October, 1971, soon after the study’s completion—and before a single methodologically and analytically rigorous result had been published—Zimbardo was asked to testify before Congress about prison reform. His dramatic testimony , even as it clearly explained how the experiment worked, also allowed listeners to overlook how coercive the environment really was. He described the study as “an attempt to understand just what it means psychologically to be a prisoner or a prison guard.” But he also emphasized that the students in the study had been “the cream of the crop of this generation,” and said that the guards were given no specific instructions, and left free to make “up their own rules for maintaining law, order, and respect.” In explaining the results, he said that the “majority” of participants found themselves “no longer able to clearly differentiate between role-playing and self,” and that, in the six days the study took to unfold, “the experience of imprisonment undid, although temporarily, a lifetime of learning; human values were suspended, self-concepts were challenged, and the ugliest, most base, pathological side of human nature surfaced.” In describing another, related study and its implications for prison life, he said that “the mere act of assigning labels to people, calling some people prisoners and others guards, is sufficient to elicit pathological behavior.”

Zimbardo released video to NBC, which ran a feature on November 26, 1971. An article ran in the Times Magazine in April of 1973. In various ways, these accounts reiterated the claim that relatively small changes in circumstances could turn the best and brightest into monsters or depersonalized serfs. By the time Zimbardo published a formal paper about the study , in a 1973 issue of the International Journal of Crim__i__nology and Penology , a streamlined and unequivocal version of events had become entrenched in the national consciousness—so much so that a 1975 methodological critique fell largely on deaf ears.

Forty years later, Zimbardo still doesn’t shy away from popular attention. He served as a consultant on the new film, which follows his original study in detail, relying on direct transcripts from the experimental recordings and taking few dramatic liberties. In many ways, the film is critical of the study: Crudup plays Zimbardo as an overzealous researcher overstepping his bounds, trying to create a very specific outcome among the students he observes. The filmmakers even underscore the flimsiness of the experimental design, inserting characters who point out that Zimbardo is not a disinterested observer. They highlight a real-life conversation in which another psychologist asks Zimbardo whether he has an “independent variable.” In describing the study to his Stanford colleagues shortly after it ended, Zimbardo recalled that conversation: “To my surprise, I got really angry at him,” he said. “The security of my men and the stability of my prison was at stake, and I have to contend with this bleeding-heart, liberal, academic, effete dingdong whose only concern was for a ridiculous thing like an independent variable. The next thing he’d be asking me about was rehabilitation programs, the dummy! It wasn’t until sometime later that I realized how far into the experiment I was at that point.”

In a broad sense, the film reaffirms the opinion of John Mark, one of the guards, who, looking back, has said that Zimbardo’s interpretation of events was too shaped by his expectations to be meaningful: “He wanted to be able to say that college students, people from middle-class backgrounds ... will turn on each other just because they’re given a role and given power. Based on my experience, and what I saw and what I felt, I think that was a real stretch.”

If the Stanford Prison Experiment had simulated a less brutal environment, would the prisoners and guards have acted differently? In December, 2001 , two psychologists, Stephen Reicher and Alexander Haslam, tried to find out. They worked with the documentaries unit of the BBC to partially recreate Zimbardo’s setup over the course of an eight-day experiment. Their guards also had uniforms, and were given latitude to dole out rewards and punishments; their prisoners were placed in three-person cells that followed the layout of the Stanford County Jail almost exactly. The main difference was that, in this prison, the preset expectations were gone. The guards were asked to come up with rules prior to the prisoners’ arrival, and were told only to make the prison run smoothly. (The BBC Prison Study, as it came to be called, differed from the Stanford experiment in a few other ways, including prisoner dress; for a while, moreover, the prisoners were told that they could become guards through good behavior, although, on the third day, that offer was revoked, and the roles were made permanent.)

Within the first few days of the BBC study, it became clear that the guards weren’t cohering as a group. “Several guards were wary of assuming and exerting their authority,” the researchers wrote. The prisoners, on the other hand, developed a collective identity. In a change from the Stanford study, the psychologists asked each participant to complete a daily survey that measured the degree to which he felt solidarity with his group; it showed that, as the guards grew further apart, the prisoners were growing closer together. On the fourth day, three cellmates decided to test their luck. At lunchtime, one threw his plate down and demanded better food, another asked to smoke, and the third asked for medical attention for a blister on his foot. The guards became disorganized; one even offered the smoker a cigarette. Reicher and Haslam reported that, after the prisoners returned to their cells, they “literally danced with joy.” (“That was fucking sweet,” one prisoner remarked.) Soon, more prisoners began to challenge the guards. They acted out during roll call, complained about the food, and talked back. At the end of the sixth day, the three insubordinate cellmates broke out and occupied the guards’ quarters. “At this point,” the researchers wrote, “the guards’ regime was seen by all to be unworkable and at an end.”

Taken together, these two studies don’t suggest that we all have an innate capacity for tyranny or victimhood. Instead, they suggest that our behavior largely conforms to our preconceived expectations. All else being equal, we act as we think we’re expected to act—especially if that expectation comes from above. Suggest, as the Stanford setup did, that we should behave in stereotypical tough-guard fashion, and we strive to fit that role. Tell us, as the BBC experimenters did, that we shouldn’t give up hope of social mobility, and we act accordingly.

This understanding might seem to diminish the power of the Stanford Prison Experiment. But, in fact, it sharpens and clarifies the study’s meaning. Last weekend brought the tragic news of Kalief Browder’s suicide . At sixteen, Browder was arrested, in the Bronx, for allegedly stealing a backpack; after the arrest, he was imprisoned at Rikers for three years without trial . (Ultimately, the case against him was dismissed.) While at Rikers, Browder was the object of violence from both prisoners and guards, some of which was captured on video . It’s possible to think that prisons are the way they are because human nature tends toward the pathological. But the Stanford Prison Experiment suggests that extreme behavior flows from extreme institutions. Prisons aren’t blank slates. Guards do indeed self-select into their jobs, as Zimbardo’s students self-selected into a study of prison life. Like Zimbardo’s men, they are bombarded with expectations from the first and shaped by preëxisting norms and patterns of behavior. The lesson of Stanford isn’t that any random human being is capable of descending into sadism and tyranny. It’s that certain institutions and environments demand those behaviors—and, perhaps, can change them.

Philip Zimbardo defends the Stanford Prison Experiment, his most famous work

What’s the scientific value of the Stanford Prison Experiment? Zimbardo responds to the new allegations against his work.

by Brian Resnick

For decades, the story of the famous Stanford Prison Experiment has gone like this: Stanford professor Philip Zimbardo assigned paid volunteers to be either inmates or guards in a simulated prison in the basement of the school‘s psychology building. Very quickly, the guards became cruel, and the prisoners more submissive and depressed. The situation grew chaotic, and the experiment, meant to last two weeks, had to be ended after five days.

The lesson drawn from the research was that situations can bring out the worst in people. That, in the absence of firm instructions of how to act, we’ll act in accordance to the roles we’re assigned. The tale, which was made into a feature film , has been a lens through which we can understand human-rights violations, like American soldier’s maltreatment of inmates at the Abu Ghraib in Iraq in the early 2000s.

This month, the scientific validity of the experiment was boldly challenged. In a thoroughly reported exposé on Medium, journalist Ben Blum found compelling evidence that the experiment wasn’t as naturalistic and un-manipulated by the experimenters as we’ve been told.

A recording from the experiment reveals that the “warden,” a research assistant, told a reluctant guard that “the guards have to know that every guard is going to be what we call a ‘tough guard.’” The warden implored the guard to act tough because “we hope will come out of the study is a very serious recommendation for [criminal justice] reform.” The implication being that if the guard didn’t play the part, the study would fail.

Additionally, one of the “prisoners” in the study told Blum that he was “acting” during a what was observed to be a mental breakdown.

These new findings don’t mean that everything that happened in the experiment was theater. The “prisoners” really did rebel at one point, and the “guards” were cruel. But the new evidence suggests that the main conclusion of the experiment — the one that has been republished in psychology textbooks for years — doesn’t necessarily hold up. Zimbardo stated over and over the behavior seen in the experiment was the result of their own minds conforming to a situation. The new evidence suggests there was a lot more going on.

I wrote a piece highlighting Blum’s exposé and putting the prison experiment in the larger context of psychology’s replication crisis. Our headline stated “we just learned it [the Stanford Prison Experiment] was a fraud.”

Fraud is a moral judgment. And Zimbardo, now a professor emeritus, wrote to Vox, unhappy with this characterization of his study. (You can Zimbardo’s full written response to the criticisms here .)

So I called Zimbardo up to ask about the evidence in Blum’s piece. I also wanted to know: As a scientist, what do you do when the narrative of your most famous work changes dramatically and spirals out of your own control?

The conversation was tense. At one point, Zimbardo threatened to hang up.

Zimbardo believes Blum (and Vox) got the story wrong. He says only one guard was prodded to act tougher. (We did not discuss Blum’s evidence that the “prisoners” in the experiment were held against their will, despite pleas to leave.)

After talking with him, the results of the prison experiment still seem unscientific and untrustworthy. It’s an interesting demonstration, but should enduring lessons in psychology be based off of it? I doubt it.

Here’s our conversation, which has been edited for length and clarity.

Brian Resnick

Here’s my understanding of the criticisms that have come to light recently about the Stanford Prison Experiment.

For years, the conclusion that has been drawn from the study was that circumstances can bring out the worst in people or encourage bad behavior. And when some people are given power, and some people are stripped of it, that fosters ugly behavior.

What’s comes to light — what I got out of that Ben Blum’s report — was that it might not have all been the circumstance. That these guards that you employed were possibly coached in some ways.

There’s audio. And for me, it sounded pretty compelling that the warden in your experiment, who I understand was an experimental collaborator — was calling out a guard for not being tough enough. [The warden told the guard, “The guards have to know that every guard is going to be what we call a ‘tough guard.’” Listen to the tape here .]

So does that not invalidate the conclusion?

Philip Zimbardo

Not at all!

And why not?

Because he’s talking to one guard who was doing nothing. These are people we’ve hired who are doing it for a salary, $15 a day, to play the role of guard. And Jaffe [the warden] picks on this guy because he is doing nothing. He’s sitting on the sideline, doing nothing, watching. He’s gotta earn his keep as a guard.

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.

Here’s the description of the experiment as written on your website: It says “the guards made up their own set of rules which they carried into effect.” In another paper , you wrote that the guards’ behavior was left up “to each subject’s prior societal learning of the meaning of prisons.”

But here’s a different possibility: Do you think it is possible that some of these guards were acting to please you, to please the study, and to do something good for science?

Even without telling the guards to explicitly do something, they might have gotten the impression that it was important for them to play these roles. And they were compelled to because of your authority.

Some of them might, but I think most of them didn’t.

For many of them, it was simply a way to make $15 a day during a two-week summer break between summer school and the start of classes in September. It was nothing more than that. It was not wanting to help science.

Some of them were increasingly mean, cruel, and sadistic way beyond any definition of tough. Some of them were guards who simply enforced the rules. And some of them were “good guards” who never did anything abusive to the prisoners. So it’s not that the situation brought a single quality in the guard. It’s a mix.

The criticism that you’re raising, that Blum raised, that others are raising, is that we told the guards to do what they ended up doing. And therefore, [the results were due to] obedience to authority, and it’s not the evolution of cruel behavior in the situation of a prison-like environment.

And I reject that.

Is it possible that some of the “prisoners” in your experiment were acting, playing along?

Zero? How can you say zero?

Okay, I can’t say.

I mean, the point was they locked themselves in their cells, they ripped off their numbers, they’re yelling and cursing at the guards. So, yeah, they could be acting. But why would they be acting. ... What would they get out of that?

Blum quoted one of the prisoners, Douglas Korpi, who had a breakdown. Korpi told Blum that he was acting. That he was in the midsts of studying for the GREs and just really wanted to get out of the experiment. Korpi told Blum, “Anybody who is a clinician would know that I was faking.”

Brian, Brian, I’m telling you every fucking thing that Ben Blum said is a lie; it’s false.

Nothing Korpi said to Ben Blum has any truth, zero. Look at Quiet Rage [a documentary about the prison experiment], look at where he says, “I was overcome in that situation. I broke down, I lost control of myself.”

Retrospectively now, he’s ashamed of having broken down. So he says he “was studying the Graduate Record Exam, I was faking it, I wanted to show I could get out and liberate my colleagues,” etc, etc.

So he is the least reliable source of any information about the study, except he documents the power of the situation to get somebody who’s psychologically normal, 36 hours before, who in an experiment, knowing it’s an experiment, has an emotional “breakdown,” and had to be released.

Let’s say: Regardless of whether guards were coached or not...

Brian, I’m gonna stop you.

Can I finish the question?

A guard, a single guard, okay? When you say guards you’re slipping back into your assumption, you’re slipping back to be like Blum. A guard was coached to be tough, and end of sentence there.

[Note: As a reminder, the tape of the experiment quoted the Jaffe, the “warden,” who played a critical role in leading the experiment, as saying, “The guards have to know that every guard is going to be what we call a ‘tough guard.’” Also, as Blum discovered in the Stanford archives, Jaffe wrote in his notes , “I was given the responsibility of trying to elicit ‘tough-guard’ behavior.” Which, again, raises suspicions that the experiment wasn’t as naturalistic as the experimenters implied.]

What I want to ask is: What is the case that this experiment should be seen as anything more than an anecdote? I don’t think anyone denies its historical value. It’s an interesting demonstration. Ideas that generated from it are worthwhile to follow up on and to study more carefully. Do you think the experiment itself has a definitive scientific value? If so, what is it?

It depends what you mean by scientific value. From the beginning, I have always said it’s a demonstration. The only thing that makes it an experiment is the random assignment to prisoners and guards, that’s the independent variable. There is no control group. There’s no comparison group. So it doesn’t fit the standards of what it means to be “an experiment.” It’s a very powerful demonstration of a psychological phenomenon, and it has had relevance.

So, yes, if you want to call it anecdote, that’s one way to demean it. If you want to say, “Is it a scientifically valid conclusion?” I say ... it doesn’t have to be scientifically valid. It means it’s a conclusion drawn from this powerful, unique demonstration.

Would you agree, as a scientist, that an early demonstration of an idea is bound to be reinterpreted in time, bound to be reevaluated?

Oh, they should. The essence of science is you don’t believe anything until it has a) been replicated, or b) been critically evaluated, as the study is being done now. I’m hoping a positive consequence of all of this is a better, fuller appreciation of what happened in the Stanford prison study.

Let me just add one thing: There are many, many classic studies that are now all under attack. ... by psychologists from a very different domain. It’s curious.

I’ve talked to a lot of researchers who are interested in replication, and reevaluating past work. They want to correct the record. I think they’re scared about what happens to the credibility of science if they don’t scrutinize the classics.

And I wonder from your point of view, as a scientist, do you need to be okay with losing control of the narrative of your work as it gets reevaluated?

Of course. The moment, the moment any of it was published, the moment any of this was put online, which I did as soon as I could, I lost. ... You lose control of it. Once it’s out there it’s not in your head anymore. Once it’s out in any public forum, then, of course, I lost control of “the narrative.”

Is it a study with flaws? I was the first to admit that many, many years ago.

A study like the prison experiment might just be too big and complicated, with too many inputs, too many variables, to really nail down or understand a single, simple conclusion from it.

The single conclusion is a broad line: Human behavior, for many people, is much more under the influence of social situational variables than we had ever thought of before.

I will stand by that conclusion for the rest of my life, no matter what anyone says.

I’m just unsure if we have the evidence to say if it’s true or not.

There are other researchers who are trying to drill down more into understanding what turns bad behavior on and off. And I’m sure you’re not a fan of him, but Alexander Haslam — [a psychologist who has tried to replicate the prison experiment study, and an academic critic of Zimbardo’s conclusions]

Oh, God! ... no, no, no.

You don’t want to talk about him.

Yeah, okay, No, I don’t want to talk about [him] at all.

Well, the gist of what he and his colleagues are arguing is this: Social identity is a really powerful motivator. And it’s perhaps more influential than situational factors. And perhaps the guards in your experiment became cruel because your warden used his authority to foster a social identity within them. [Here’s a new paper with their latest arguments. ]

I reject that. No, no. That’s their shtick, that’s what they’re pushing.

You don’t assume good faith on their part?

I’m not saying good faith. That’s what their claim to fame is the importance of social identity.

Of course people have social identity. But, there’s also something called situational identity. In a particular situation, you begin to play a role. You are the boss, you are the foreman, you are the drill sergeant, you are the fraternity hazing master. And in that role, which is not the usual you, you begin to do something which is role-bound. ... This is what anybody in this role does. And your behavior then changes.

Is there experimental evidence outside the prison experiment that supports that view?

The view that situation can make a difference?

Yeah. There are plenty of examples in history and current events, but is that something we know as a fact, as an experimental fact?

I don’t know off the top of my head. ...

I’ve always said it’s an interaction. I’m an interactionist. What I’ve said, if you read any of my textbooks, it’s always an interaction between what people bring into a situation, which means genetics and personality, and what the situation brings out in you, which is a social/psychological power of some situations over others. And I will stand by that, my whole career depends on that.

It’s not like I’m mindlessly promoting the situation is dominating everybody.

What would you fear might happen if people stop believing in the integrity of the Stanford Prison Experiment?

The fear is they will lose an important conclusion about the nature of human behavior as being, to some extent, situationally influenced.

You’re afraid they’ll lose an important conclusion even though the study is just a demonstration?

You demonstrate gravity by throwing a ball up and seeing if it comes down. I think you’re insisting on a traditional view of what is scientific, what is a scientific experiment, what is a scientifically validated conclusion. And I am saying from the beginning the Stanford Prison Experiment is a unique and powerful demonstration of how social/situational variables can influence the behavior of some people, some of the time. That’s a very modest conclusion.

All of this controversy is happening now because you gave your notes and tapes from the prison experiment to the Stanford archives. That transparency is commendable. Do you regret it?

No, I don’t regret it. The reason I did it is to make it available for researchers, for anybody, and people have gone through it.

So again, the last thing in the world I need is for people to doubt my honesty, my professional credibility. That’s an attack on me personally, and that I reject and I’m arguing it’s absolutely wrong.

Is it okay if we just move on from the Stanford Prison Experiment? Like you said, it’s a demonstration. Maybe we need to ground our understanding of acts of evil in something a little bit more scientific, to be honest.

At this point, I don’t want anyone to reject that basic conclusion that I’ve said several times in this interview. I don’t want that to be rejected. I would love for there to be better, more scientific evaluation of this conclusion, rather than a bunch of bloggers saying, “We’re gonna shoot it down.”

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Table of Contents

Background and Objectives

In the 1960s and 70s, psychologist Philip Zimbardo conducted several notable social psychology experiments examining how social roles and situations can impact human behavior .

Zimbardo designed the Stanford Prison Experiment in 1971 to explore the psychology of imprisoning people. He aimed to study how participants reacted to being assigned randomized roles of prisoner and guard.

Zimbardo’s primary hypothesis was that the imposed social roles and environment of a prison would dominate the individual personalities of the participants, causing them to exhibit more extreme behaviors.

The experiment intended to demonstrate that situational variables can have a more powerful influence over behavior than inherent individual traits.

Zimbardo set up a simulated prison environment in the basement of Stanford University’s psychology building.

He recruited 18 male college students through a newspaper ad offering $15 per day to participate.

Although the participants had no abnormal psychological issues, Zimbardo hoped to provoke realistic responses by creating a believable mock prison.

The experiment planned to observe the participants’ interactions, emotions, and behaviors in this environment over a planned two-week study period.

Through this approach, Zimbardo sought to gain insight into the psychological mechanisms that make prisons dehumanizing environments.

Methodology

Zimbardo converted a corridor of the psychology department building into a simulated prison environment.

The experiment was monitored with video cameras and microphones. The participants were randomly assigned to be either “prisoners” or “guards” using a coin flip.

The “prisoners” were picked up by surprise at their homes by actual police officers, searched, handcuffed, and brought to the mock prison.

The prisoners were stripped naked, deloused, and given smocks and stocking caps to establish their powerless status.

Each prisoner was assigned an ID number to replace their name and lived in a small cell containing only a cot for sleeping.

The “guards” worked eight-hour shifts, with three guards working each shift. Guards wore military-style uniforms and reflector sunglasses to create an anonymous, authoritative appearance.

They carried handcuffs, whistles, and billy clubs. The guards followed protocols to maintain control, including bag searches, ID checks, and setting strict schedules.

However, they could otherwise run the prison however they wished and were told to demand total compliance from prisoners.

The study was scheduled to run for 14 days.

Zimbardo intended to observe how the participants interacted in these circumstances.

He took on the role of the prison superintendent, navigating how the study would proceed. Zimbardo encouraged the guards to create an oppressive atmosphere and break down the prisoners over time.

Findings and Analysis

The experiment quickly escalated out of control as the “guards” began ramping up their harassment and authoritarian measures, while the “prisoners” passively accepted the abuse.

On the second day of the experiment, the prisoners rebelled by barricading their cell doors and taunting the guards.

The guards responded by forcibly stripping the prisoners naked and removing their beds as punishment.

One prisoner developed acute emotional disturbance and had to be released after only 36 hours.

Over the next few days, the guards escalated their aggressive and dehumanizing tactics using psychological humiliation.

They set up privilege systems to make prisoners turn on each other.

Prisoners were forced to repeat their ID numbers and do meaningless chores and exercise.

Some prisoners began showing signs of depression and acute anxiety .

The guards and prisoner “#819” came into major conflict , with the prisoner launching a hunger strike.

Prisoner #819 was then subjected to further abuse.

Zimbardo interpreted the behavior results as arising from the assigned social roles and rules dominating over individual dispositions.

The prisoners became increasingly passive , depressed, and helpless as the study went on.

The phenomenon of one domineering guard nicknamed “John Wayne” emerged through the study procedures.

Zimbardo concluded the imposed prison environment crushed internal values and morals.

Criticisms and Ethical Concerns

The Stanford Prison Experiment has been widely criticized for being unscientific and unethical.

Critics point out there was no control group to compare against the prisoner and guard group.

The sample size of only 24 male participants was also too small to draw general conclusions about human behavior.

There are major ethical concerns about the amount of psychological distress inflicted on the participants.

The prisoners showed signs of anxiety, depression, and learned helplessness. Critics argue it was unethical to allow participants to continue suffering emotional harm.

The guards were encouraged to degrade the prisoners without oversight on their methods.

The experimenters became overinvolved as the study progressed rather than remaining neutral observers.

The experiment could not be conducted today with current ethical standards.

Today’s Institutional Review Boards would never allow vulnerable participants to be subjected to such dangerous psychological manipulation without proper informed consent.

Critics argue Zimbardo was irresponsible for encouraging aggression and abuse between participants.

The dramatic, uncontrolled nature of the study design would be prohibited by today’s more stringent safeguards.

Ultimately, the Stanford Prison Experiment revealed more about the problematic study procedures than any deep insights into human behavior.

While thought-provoking, the experiment is widely considered unethical and lacking in scientific rigor by today’s standards.

Legacy and Relevance Today

While the Stanford Prison Experiment faced deserved criticism, it left a legacy and continues to be referenced given the dramatics of the study.

Zimbardo’s experiment demonstrated how situational variables like social roles can override individual disposition to generate extreme behaviors.

The study shed light on how putting people in positions of power without oversight can lead to the abuse of authority.

The Stanford Prison Experiment is frequently cited when discussing the psychology of imprisonment.

The study showed how prisoners can become distressed and resigned in response to an oppressive environment.

It provided insight into how regimes like concentration camps can gain control through psychological manipulation.

However, the experiment’s scientific limitations mean its conclusions should be applied cautiously.

The study informed later research into prison conditions and supervisor/subordinate dynamics.

Modern replication attempts have used more rigorous methods and ethical standards.

However, the original experiment’s dramatic narrative keeps its themes relevant when examining topics like oppression, compliance, surveillance, and dehumanization.

Zimbardo’s prison study remains impactful despite its flaws, pioneering new areas of psychology research.

While controversial, it provided a warning about unconstrained authority that still resonates over 50 years later.

Philip Zimbardo (Biography + Experiments)

Who Is Philip Zimbardo?

Philip Zimbardo is a prominent Italian-American psychologist, author, and retired professor. He is best known for his work in the Stanford Prison Experiment—widely considered one of the most impactful and controversial social psychology experiments in history. The experiment has been the subject of conversations, classes, and even movies for years.

Philip Zimbardo Short Biography

Zimbardo was born in New York City in 1933. Zimbardo believes his interest in human behavior was sparked during his childhood. He often experienced prejudice and discrimination in those early years due to his Italian descent and poor financial background.

Despite his humble beginnings, Zimbardo completed his bachelor’s degree at Brooklyn College in 1954, with a triple major in psychology, sociology, and anthropology. He earned his Master’s degree (1955) and doctoral degree (1959) at Yale University. From 1959-2003, Zimbardo taught at a number of prestigious universities including Yale, New York University, Columbia, and Stanford.

What is The Stanford Prison Experiment?

The Stanford Prison Experiment was a study conducted in 1971 that examined how situational forces and perceived power affect human psychology. It focused primarily on the interactions and interpersonal relationships between prisoners and prison guards in a prison-like environment. The experiment was funded by the United States Office of Naval Research. The research team was led by Philip Zimbardo and included Craig Haney, W. Curtis Banks, and David Jaffe.

The experiment was conducted in the basement of the psychology building at Stanford University. After an ad was put out in the Palo Alto City newspaper, college students from all over the United States and Canada volunteered to participate. Those selected were assigned roles as either prisoners or prison guards. A mock prison with three small prison cells was constructed for the experiment.

As the study progressed, the relationship between the “prisoners” and the “prison guards” eroded drastically. Some reports suggest the prisoners were subjected to psychological torture. Several prisoners had to be released from the experiment when they were unable to cope with the deteriorating conditions. Although the study was designed to run for up to two weeks, it was brought to a premature end after just six days.

Stanford Prison Experiment Method

Twenty-four college males were recruited for the experiment. They were told the study involved a two-week prison simulation and they would be paid $15 per day. The subjects were primarily white, middle class, and had no criminal background. The researchers also took care to select participants who had no history of medical or psychological issues.

The subjects were randomly assigned as either prisoners or guards by flipping a coin. There were 9 guards (with 3 possible substitutes) and 9 prisoners (also with 3 possible substitutes). David Jaffe, who was an undergraduate research assistant at the time, served as the warden of the prison. Zimbardo played the role of superintendent.

The prison was intentionally constructed without windows or clocks. Each prison cell measured 6 x 9 feet, contained three cots, and held three prisoners. A long corridor (boarded up at each end) served as the "yard" for the prisoners. A small closet was used as the "hole" for solitary confinement.

The prisoners wore nylon stocking caps, a loose-fitting dress with an identification number, a heavy chain around their right ankle, rubber sandals, and no underclothes. Being forced to wear a dress immediately led to some prisoners having to sit more like a woman than a man. The prison attire was specially chosen to emasculate, humiliate, and oppress the inmates. The nylon caps symbolized their hair being shaved off and minimized their individuality.

Guards were given identical khaki uniforms, mirrored sunglasses to prevent eye-contact, a whistle, and a baton to symbolize their power. Their clothing gave them a sense of authority and anonymity. They were also given much more space than the prisoners as well as rest periods, personal comforts, and areas for relaxation. The guards received no formal training on prison management.

Rules of the Study

Before the study began, the guards were told not to harm the prisoners physically, or limit their food and water. However, they were allowed to induce fear or boredom in the prisoners, as well as take away their privacy. Rather than address the prisoners by name, the guards were instructed to call them by their identification numbers. Zimbardo designed the experiment to (1) give the guards the feeling of complete control and (2) rob the prisoners of their sense of reality, time, space, and self.

On the first day of the experiment, the Palo Alto police department assisted Zimbardo by arresting the prisoners at their homes and taking them through the entire booking process. The prisoners were charged with crimes, given their Miranda warning, handcuffed, fingerprinted, and photographed. The sudden, unexpected arrest left many of the prisoners in mild shock. After booking they were blindfolded and placed in a holding cell at the police station until pickup.

When the prisoners arrived at the mock prison they were strip searched and deloused. The purpose was to humiliate them and ensure no pests were introduced into the prison. Three guards worked at a time in eight hour shifts. The prisoners were forced to remain on site as they needed to be locked up for the majority of the experiment.

Results of the Stanford Prison Experiment

While the first day of the study ended without any major incident, the second day began with a riot. Some of the prisoners decided to block the cell doors with their beds. In a show of defiance, they discarded their caps and tore off their prison numbers. They also hurled insults at the guards.

With three guards finding it difficult to manage nine prisoners, the guards from the other shifts agreed to help end the riot. They eventually used a fire extinguisher to douse the prisoners in ice cold carbon dioxide and forced them away from the doors. Once inside the cells, the guards stripped the prisoners and took away their beds. The ringleaders were forced into solitary confinement.

Upon realizing that they were outnumbered on each shift, the guards decided to attack the prisoners psychologically in order to strengthen their control over them. Prisoners who did not actively participate in the revolt were placed in a “privilege cell” that offered clothing, better food, beds, and the opportunity to wash and brush their teeth. However, the prisoners in the privileged cell were soon replaced with prisoners who were in the "bad" cells. This tactic was used to confuse the prisoners and break their unity.

As a part of their psychological attack, the guards instructed the prisoners to memorize and repeat their assigned numbers throughout the day. This was usually done during the numerous prisoner counts. The guards also forced the prisoners to refer to each other by number. This tactic helped to deindividualize the prisoners and bolstered the idea that their numbers were their new identity.

Approximately 35 hours into the experiment, one prisoner—identified as #8612—began to scream, curse, and lash out in rage. The researchers were eventually forced to released him from the study as he showed signs of depression, disorganized thinking, and uncontrollable crying.

Increasing Cruelty

The researchers noted that as the experiment went on, the guards treated the prisoners with increasing cruelty. The guards developed a series of methods for punishing the prisoners which included:

Doing tedious, meaningless work
Refusing requests to go to the bathroom
Not being allowed to empty their sanitation buckets (which were kept in the cells)
Solitary confinement
Sleep deprivation
Cleaning toilets with their hands
Cursing each other publicly
Wearing a paper bag over their heads
Laughing, singing or smiling on command
Doing pushups, sometimes with a guard's foot on their backs
Picking thorns out of their blankets (the blankets were dragged through thorn bushes by the guards)

All In on the Experiment

On day three, the guards became concerned after hearing a rumor that released prisoner #8612 planned to return with friends to break the other inmates out of prison. The researchers, who were now completely caught up in the experiment themselves, took steps to thwart the attack by moving the prison out of the basement to another floor. Zimbardo also planned to intercept the attackers and tell them that the study had ended. However, the attackers never showed up and the prison was moved back to the basement.

The longer the experiment went on, the more absorbed the participants and the researchers became. One guard who felt sorry for the prisoners and wanted to help them was encouraged by “warden” David Jaffe to get more involved and get tougher. By day five, three additional prisoners had to be released from the study because they showed signs of anxiety. A fifth inmate developed a psychosomatic rash over his entire body after his "parole" was rejected by a mock parole board. He too was released from the experiment.

Solitary Confinement

When prisoner #416—a newly admitted participant—refused to eat, he was subjected to increased abuse from the guards. When the guards were unable to force him to eat, #416 was put in solitary confinement. He was only allowed to return to his cell after seven of the other eight prisoners agreed to give up their blankets.

While the prisoners had shown solidarity during the first rebellion on day two, they now regarded #416 as just a trouble-maker. The unity among the inmates had completely deteriorated. In many cases they obeyed the guards blindly, even when the instructions were unjust. It appeared as if all the participants had forgotten that this was just an experiment.

Why Did the Stanford Prison Experiment End Early?

The study was brought to an abrupt end on day six. Christina Maslach—a graduate student in psychology and Zimbardo’s girlfriend at the time—arrived on site to conduct a series of interviews with the subjects. When she saw the condition the prisoners were in, her immediate reaction was one of shock and disgust. The Stanford Prison Experiment was discontinued later that day after Maslach strongly questioned the morality of the study.

Conclusions from the Stanford Prison Experiment

The study highlighted how certain social contexts can significantly influence or transform human behavior. Although all the subjects had been carefully screened across a variety of physical and personality measures before the study, it did not take long for them to act in a manner neither they nor the researchers expected. Some guards became increasingly cruel and sadistic in their efforts to harass the prisoners. The other guards gave off an air of indifference and did nothing to stop the mistreatment.

The prisoners also showed drastic changes in behavior due to the psychological trauma they experienced. Some inmates begged to be released from prison shortly after the experiment started and most of them were willing to obey even the most unreasonable commands from the guards. Zimbardo believed that the participants’ change in behavior was because they had begun to internalize their assigned roles . As the experiment went on, the guards increasingly believed they had the authority to do anything they wanted within the confines of the prison and the prisoners increasingly thought of themselves as less than important than the guards.

The goal of the Stanford Prison Experiment was to show how prison-like environments could influence the people who pass through them. It clearly demonstrated how insane situations can lead to insane behaviors from normal people. It also highlighted the power of perceived authority, the pressure individuals face to conform to their assigned social group , and how people may respond to cognitive dissonance .

The researchers believed the behavior of the students greatly mirrored the behavioral patterns found in actual prisons. Several insights from the experiment were adopted by the United States government to improve the management of correctional facilities across the nation.

Criticism and Limitations of The Stanford Prison Experiment

Over the years, an increasing number of people have expressed concerns about the ethics of the Stanford Prison Experiment. Many critics were appalled that young men were subjected to psychological torture for days in the name of social psychology. The extremely unsanitary condition of the mock prison also raised concerns about the physical health of the inmates. The fact that the guards were able to find ways to harass the prisoners without being supervised by the research team was another safety issue that was not adequately addressed before or during the study.

Several critics argued that the experiment lacked scientific rigor and produced no real results. They believe the behavior of the students was influenced by the fact that they knew they were being observed. Rather than a behavioral change occurring naturally, some opponents point to the fact that Zimbardo explicitly instructed the guards to use psychological tactics. After the study, one guard commented that he behaved the way he did because he wanted the researchers to get good data they could work with.

Later reports even show that the guards were instructed to "act tough."

Zimbardo himself admitted that the study did not measure up to the standards of a scientific experiment as it did not have a control group, a comparison group, or other defined variables. Rather than a rigorous scientific experiment, Zimbardo asserted that his study was a valid demonstration of what can happen to human behavior in certain social contexts.

Replications of Stanford Prison Experiment

A number of researchers have tried to replicate the Stanford Prison Experiment in the decades that followed. But although they copied Zimbardo’s methodology, they were not able to replicate his findings. However, real-world events at Abu Ghraib prison brought the Stanford Prison Experiment back to public attention in 2004. The sadistic acts committed by several United States military personnel at the Iraqi prison almost perfectly mirrored Zimbardo's 1971 study.

Zimbardo’s Other Interests, Contributions, and Awards

After the Stanford Prison Experiment, Zimbardo delved into other areas of social psychology that interested him. This included in-depth research on topics such as the psychology of shyness, evil, violence, terrorism, heroism, madness, persuasion, hypnosis, dissonance, and time perspective. He has written several books on his findings and some of his research papers are considered required reading for a number of psychology courses today. In 2012, he was awarded the American Psychological Foundation Gold Medal for Lifetime Achievement in the Science of Psychology.

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. Retrieved from https://www.gvsu.edu/cms4/asset/F51281F0-00AF-E25A-5BF632E8D4A243C7/stanford_prison_experiment.pdf

O’Toole, K. (1997, January 8). The stanford prison experiment: Still powerful after all these years. Retrieved from https://news.stanford.edu/pr/97/970108prisonexp.html

Philip. G. Zimbardo. (2016, September 8). Retrieved from http://zimbardo.socialpsychology.org/

The Story: An Overview of the Experiment. (n.d.). Retrieved from https://www.prisonexp.org/

Zimbardo, P., Haney, C., Banks, W. C. & Jaffe, D. (1971). The stanford prison experiment: A simulation study of the psychology of imprisonment. Retrieved from https://web.stanford.edu/dept/spec_coll/uarch/exhibits/Narration.pdf

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Inside the prison experiment that claimed to show the roots of evil

The Stanford prison experiment was the classic demonstration of how power can bring out the worst in us. But now it seems it was more about showbiz than science

By Gina Perry

10 October 2018

Philip Zimbardo in 1971. He is now 85 and still gives talks

Duke Downey/Polaris/eyevine

IN A darkened auditorium in September 2008, I sat in the audience awaiting the start of a presentation entitled “The psychology of evil” by social psychologist Philip Zimbardo. Suddenly, the doors at the back of the theatre burst open, lights flashed and Santana’s song Evil Ways blared from the speakers. A man with slicked-back black hair and a devilish pointy beard danced up the aisle towards the stage, snapping his fingers in time with the music. Zimbardo’s flamboyant entrance was startling, given the nature of the talk.

I shouldn’t have been surprised. Zimbardo’s knack for performance is one of the reasons his Stanford prison experiment is one of the most famous psychological studies of the 20th century, alongside research into obedience carried out by his high-school classmate, Stanley Milgram .

Eschewing conventional academic reporting, Zimbardo’s first account of the experiment was a sensational piece that appeared in a supplement of The New York Times , showcasing his skill as a storyteller. The article kicked off by detailing how, one sunny morning in Palo Alto, California, in 1971, police swooped on the homes of nine young men. They were bundled into squad cars, taken to the police station, charged, then blindfolded and transported to the Stanford County Jail, where they met their guards.

The “jail” was actually a set-up in the basement of a building at Stanford University. The prisoners were one half of a group of volunteers, the other half being assigned the role of guards. In what Zimbardo described as “a gradual Kafkaesque metamorphosis of good into evil”, these seemingly well-adjusted young men became increasingly brutal as guards. They “repeatedly stripped their prisoners naked, hooded them, chained them, denied them food or bedding privileges, put them into solitary confinement, and made them clean toilet bowls with their bare hands”, Zimbardo wrote. “Over time, these amusements took a sexual turn, such as having the prisoners simulate sodomy on each other.” The prisoners, humiliated and victimised, suffered such emotional distress that Zimbardo, playing the role of all-powerful prison superintendent, terminated the two-week experiment after just six days.

The experience made the key players famous – not least because Zimbardo captured some of the experiment on film and in now-familiar photos. The images showed aggressive-looking guards in tinted aviator shades, clutching police batons, and cowed, shackled prisoners sitting in line with bags over their heads.

The Stanford prison experiment in 1971 started with lifelike arrests of volunteers

Philip G. Zimbardo

The experiment led Zimbardo to conclude that normal people could be transformed into sadistic tyrants or passive slaves, not because of any inherent personality flaws but through finding themselves in a dehumanising environment: context was king. And suddenly, so was Zimbardo. Overnight, he became the go-to expert on prison reform, and over the following decade he appeared at a series of Congressional hearings and advisory panels on the US prison system.

The Stanford experiment might have started as a psychological exploration of incarceration, but Zimbardo and countless media commentators since have reached for it to illuminate an ever-widening range of behaviours – police brutality, corporate fraud, domestic abuse, genocide. Every invocation of the experiment has cemented it in the public imagination. The experiment has become enshrined in the psychology curriculum for its simple and compelling conclusion, that corrupt environments can turn good people evil. And of course it has made the leap to popular culture, inspiring documentaries, books and dramatisations. The most recent feature film based on it was 2015’s The Stanford Prison Experiment , for which Zimbardo was a consultant.

Battered credibility

Zimbardo was elected president of the American Psychological Association in 2002 and in 2012 received the American Psychological Foundation’s gold medal for lifetime achievement. Despite Zimbardo’s recognition and career honours, and his experiment being in all the textbooks, academic psychology is ambivalent about it. Not surprising, given that the experiment’s scientific credibility has taken a battering.

On the one hand, with his high profile and media know-how, Zimbardo has done much to promote social psychology. On the other, the experiment’s ethics, methodology and conclusions have long troubled colleagues. The first published criticism, in 1973, attacked the ethics of the study and questioned whether the apparent degradation of the young men was justified, given the experiment’s unsurprising result. By 1975, the methodology of the experiment was also under fire. Zimbardo’s claims that the results support the view that behaviour is determined by circumstances, not personality have also been robustly challenged by a growing number of researchers since then. After all, critics argued, the guards’ behaviour was hardly spontaneous: they knew they were expected to behave like tyrants and were encouraged to do so. And by Zimbardo’s own admission, two-thirds of them did not act sadistically, undermining his claim that the situation had an overpowering influence on their actions.

How did a study so flawed become so famous? First, there’s the powerful idea that evil lurks inside us all, waiting for the right – or wrong – circumstances to be called forth. The experiment itself may be shocking, but the way it echoes archetypal stories of sinfulness make it hard to shake off.

Then there is Zimbardo himself, a compelling narrator who inserts himself front-and-centre in the drama. In that first published account, Zimbardo admitted to a growing sense of unease over his role as architect of an experiment of such cruelty. His epiphany – helped along by a visit from his then girlfriend, who was appalled at his behaviour – that he too had been corrupted by power was what prompted him to call the experiment off. This acceptance of blame both disarms critics of the ethics of the experiment and suggests that we can trust him to give an unvarnished account of the research. There are echoes of biblical conversion stories; Zimbardo’s subsequent involvement in prison reform and more recently in a project to train ordinary people to become “heroes” are a form of atonement. “I want to be remembered not as Dr Evil,” Zimbardo tells me, “but as Dr Good.”

His public performances, TV appearances and TED talks have an evangelical flavour . Let’s face it, “good vs evil” sells, and it circumvents the hassle of trying to understand the subtleties of human psychology.

Zimbardo also has a talent for reframing the “lessons” of the Stanford experiment to capture the prevailing zeitgeist. In 2004, the study made the headlines when it emerged that American military police had abused and tortured prisoners inside Iraq’s Abu Ghraib prison . The public debate about how US soldiers could behave so appallingly raised comparisons with the experiment, rekindling Zimbardo’s career as a government-appointed expert. In a Boston Globe editorial, he wrote, “ The terrible things my guards [at Stanford] did to their prisoners were comparable to the horrors inflicted on the Iraqi detainees .” In reality, the terrifying and degrading acts of physical, psychological and sexual abuse meted out at Abu Ghraib were way beyond anything experienced by Zimbardo’s prisoners.

Philip Zimbardo captured the degradation of prisoners in his experiment on film

Chuck Painter/Stanford News Service

But this fresh attention sparked a more critical examination by journalists, who bypassed Zimbardo and sought out the people who took part. Cracks soon appeared in Zimbardo’s tightly controlled narrative.

In interviews with researchers and participants, an alternative story emerged. In a 2004 article in the Los Angeles Times , journa list Alan Zarembo reported that “prisoner” Douglas Korpi was disgusted with the experiment and Zimbardo’s exploitation of it. Both Korpi and Dave Eshelman, who was often depicted as one of the more sadistic guards , spoke of a staged “experiment”, and that they had behaved in order to fulfil their role as paid participants. That undermined Zimbardo’s insistence that his participants unquestioningly accepted the reality of the dramatic situation.

In 2011, Zimbardo admitted the study’s limitations . “It wasn’t a formal experiment. My colleagues probably never thought much of it,” he told an interviewer. In a high-profile blog post in 2013, textbook author Peter Gray decried the inclusion of the experiment in the teaching of psychology, and later called it “an embarrassment to the field”.

In April this year, French author Thibault Le Texier published the book Histoire d’un Mensonge (“History of a Lie”). Le Texier compared archival records with Zimbardo’s published accounts, listened to audio recordings and video footage of the experiment that had been edited out of public presentations, and interviewed research staff, former “guards” and “prisoners”. He concluded that Zimbardo’s claims were overblown and his findings hollow.

In a subsequent article on the Medium website , journalist Ben Blum confronted Zimbardo with the contradictions Le Texier had uncovered. Zimbardo pointed to the fame of the experiment as his defence. He later published a rebuttal on his website, infuriating critics of his research by dismissing them as “bloggers” and labelling their findings “differences in interpretation”. Only time will tell if these recent revelations will diminish the experiment in the public imagination.

If social psychology can be said to have attained the status of religious teachings, then Zimbardo is one of the field’s best-known preachers. And like a good preacher, Zimbardo represents the story of the experiment as a timeless parable. “Famous studies like Milgram’s obedience to authority, Mischel’s marshmallow test, the Stanford prison experiment, they raise moral issues and offer lessons about the psychology of temptation,” Zimbardo tells me. “Think about the Lord’s prayer. What is the key line? ‘Lead us not into temptation, but deliver us from evil.’ There are temptations all around us, and who gives in and who resists, this is a fundamental thing about human nature. This is what all these experiments explore and that gives them great public appeal.”

“I want to be remembered not as Doctor Evil, but as Doctor Good”

In his 2007 bestseller The Lucifer Effect , Zimbardo appealed to readers to look inwards. “Could we, like God’s favourite angel, Lucifer, ever be led into the temptation to do the unthinkable to others?” He promised readers a journey that will take in “genocide in Rwanda, the mass suicide and murder of People’s Temple followers in the jungles of Guyana, the My Lai massacre in Vietnam, the horrors of Nazi concentration camps, the torture by military and civilian police around the world, and the sexual abuse of parishioners by Catholic priests…” Then he adds that the “one… thread tying these atrocities together” comes from “the Stanford Prison Experiment”.

Through his story of a descent into the basement hell, the suffering, the epiphany, the ascent, transformation and redemption, Zimbardo offers a powerful message of hope about human nature: we all have the potential to be saints rather than sinners. It’s seductive to think that in the fight between good and evil we can all be winners through the redemptive power of psychological knowledge. Shame that, as far the Stanford prison experiment is concerned, it’s more showbiz than science.

This article appeared in print under the headline “The evil inside us all”

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Conformity to Social Roles as Investigated by Zimbardo

Last updated 22 Mar 2021

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Zimbardo (1973) conducted an extremely controversial study on conformity to social roles, called the Stanford Prison Experiment.

His aim was to examine whether people would conform to the social roles of a prison guard or prisoner, when placed in a mock prison environment. Furthermore, he also wanted to examine whether the behaviour displayed in prisons was due to internal dispositional factors, the people themselves, or external situational factors, the environment and conditions of the prison.

Zimbardo’s sample consisted of 21 male university students who volunteered in response to a newspaper advert. The participants were selected on the basis of their physical and mental stability and were each paid $15 a day to take part. The participants were randomly assigned to one of two social roles, prisoners or guards.

Zimbardo wanted to make the experience as realistic as possible, turning the basement of Stanford University into a mock prison. Furthermore, the ‘prisoners’ were arrested by real local police and fingerprinted, stripped and given a numbered smocked to wear, with chains placed around their ankles. The guards were given uniforms, dark reflective sunglasses, handcuffs and a truncheon. The guards were instructed to run the prison without using physical violence. The experiment was set to run for two weeks.

Zimbardo found that both the prisoners and guards quickly identified with their social roles. Within days the prisoners rebelled, but this was quickly crushed by the guards, who then grew increasingly abusive towards the prisoners. The guards dehumanised the prisoners, waking them during the night and forcing them to clean toilets with their bare hands; the prisoners became increasingly submissive, identifying further with their subordinate role.

Five of the prisoners were released from the experiment early, because of their adverse reactions to the physical and mental torment, for example, crying and extreme anxiety. Although the experiment was set to run for two weeks, it was terminated after just six days, when fellow postgraduate student Christina Maslach convinced Zimbardo that conditions in his experiment were inhumane. [Maslach later became Zimbardo’s wife].

Zimbardo concluded that people quickly conform to social roles, even when the role goes against their moral principles. Furthermore, he concluded that situational factors were largely responsible for the behaviour found, as none of the participants had ever demonstrated these behaviours previously.

Evaluation of Zimbardo

A recent replication of the Stanford Prison Experiment, carried out by Reicher and Haslam (2006), contradicts the findings of Zimbardo.

Reicher and Haslam replicated Zimbardo’s research by randomly assigning 15 men to the role of prisoner or guard. In this replication, the participants did not conform to their social roles automatically. For example, the guards did not identify with their status and refused to impose their authority; the prisoners identified as a group to challenge the guard’s authority, which resulted in a shift of power and a collapse of the prison system. These results clearly contradict the findings of Zimbardo and suggest that conformity to social roles may not automatic, as Zimbardo originally implied.

Furthermore, individual differences and personality also determine the extent to which a person conforms to social roles. In Zimbardo’s original experiment the behaviour of the guards varied dramatically, from extremely sadistic behaviour to a few good guards who helped the prisoners. This suggests that situational factors are not the only cause of conformity to social roles and dispositional factors also play a role.

Zimbardo’s experiment has been heavily criticised for breaking many ethical guidelines, in particular, protection from harm. Five of the prisoners left the experiment early because of their adverse reactions to the physical and mental torment. Furthermore, some of the guards reported feelings of anxiety and guilt, as a result of their actions during the Stanford Prison Experiment. Although Zimbardo followed the ethical guidelines of Stanford University and debriefed his participants afterwards, he acknowledged that the study should have been stopped earlier.

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Demonstrating the Power of Social Situations via a Simulated Prison Experiment

A person-centered analysis of human behavior attributes most behavior change, in positive or negative directions, to internal, dispositional features of individuals. The factors commonly believed to direct behavior are to be found in the operation of genes, temperament, personality traits, personal pathologies and virtues. A situation-centered approach, in contrast, focuses on factors external to the person, to the behavioral context in which individuals are functioning. Although human behavior is almost always a function of the interaction of person and situation, social psychologists have called attention to the attributional biases in much of psychology and among the general public that overestimates the importance of dispositional factors while underestimating situational factors. This "fundamental attribution error" they argue, leads to a misrepresentation of both causal determinants and means for modifying undesirable behavior patterns. Research by social psychologist Stanley Milgram, PhD, (1974; see also Blass, 1999) was one of the earliest demonstrations of the extent to which a large sample of ordinary American citizens could be led to blindly obey unjust authority in delivering extreme levels of shock to an innocent "victim."

The Stanford Prison Experiment extended that analysis to demonstrate the surprisingly profound impact of institutional forces on the behavior of normal, healthy participants. Philip Zimbardo, PhD, and his research team of Craig Haney, Curtis Banks, David Jaffe, and ex convict consultant, Carlo Prescott (Zimbardo, Haney, Banks, & Jaffe, 1973) designed a study that separated the usual dispositional factors among correctional personnel and prisoners from the situational factors that characterize many prisons. They wanted to determine what prison-like settings bring out in people that are not confounded by what people bring into prisons. They sought to discover to what extent the violence and anti-social behaviors often found in prisons can be traced to the "bad apples" that go into prisons or to the "bad barrels" (the prisons themselves) that can corrupt behavior of even ordinary, good people.

The study was conducted this way: College students from all over the United States who answered a city newspaper ad for participants in a study of prison life were personally interviewed, given a battery of personality tests, and completed background surveys that enabled the researchers to pre-select only those who were mentally and physically healthy, normal and well adjusted. They were randomly assigned to role-play either prisoners or guards in the simulated prison setting constructed in the basement of Stanford University's Psychology Department. The prison setting was designed as functional simulation of the central features present in the psychology of imprisonment (Zimbardo, Maslach, & Haney, 1999). Read a full description of the methodology, chronology of daily events and transformations of human character that were revealed.

The major results of the study can be summarized as: many of the normal, healthy mock prisoners suffered such intense emotional stress reactions that they had to be released in a matter of days; most of the other prisoners acted like zombies totally obeying the demeaning orders of the guards; the distress of the prisoners was caused by their sense of powerlessness induced by the guards who began acting in cruel, dehumanizing and even sadistic ways. The study was terminated prematurely because it was getting out of control in the extent of degrading actions being perpetrated by the guards against the prisoners - all of whom had been normal, healthy, ordinary young college students less than a week before.

Significance

Practical application.

The lessons of the Stanford Prison Experiment have gone well beyond the classroom (Haney & Zimbardo, 1998). Zimbardo was invited to give testimony to a Congressional Committee investigating the causes of prison riots (Zimbardo, 1971), and to a Senate Judiciary Committee on crime and prisons focused on detention of juveniles (Zimbardo, 1974). Its chair, Senator Birch Bayh, prepared a new law for federal prisons requiring juveniles in pre-trial detention to be housed separately from adult inmates (to prevent their being abused), based on the abuse reported in the Stanford Prison Experiment of its juveniles in the pre-trial detention facility of the Stanford jail.

A video documentary of the study, "Quiet Rage: the Stanford Prison Experiment," has been used extensively by many agencies within the civilian and military criminal justice system, as well as in shelters for abused women. It is also used to educate role-playing military interrogators in the Navy SEAR program (SURVIVAL, EVASION, and RESISTANCE) on the potential dangers of abusing their power against others who role-playing pretend spies and terrorists (Zimbardo, Personal communication, fall, 2003, Annapolis Naval College psychology staff).

The eerily direct parallels between the sadistic acts perpetrator by the Stanford Prison Experiment guard and the Abu Ghraib Prison guards, as well as the conclusions about situational forces dominating dispositional aspects of the guards' abusive behavior have propelled this research into the national dialogue. It is seen as a relevant contribution to understanding the multiple situational causes of such aberrant behavior. The situational analysis of the Stanford Prison Experiment redirects the search for blame from an exclusive focus on the character of an alleged "few bad apples" to systemic abuses that were inherent in the "bad barrel" of that corrupting prison environment.

Cited Research

Blass, T. (Ed.) ( 1999). Obedience to Authority: Current Perspectives on the Milgram Paradigm. Mahwah, NJ: Erlbaum.

Haney, C. & Zimbardo, P.G., (1998). The Past and Future of U.S. Prison Policy. Twenty-Five Years After the Stanford Prison Experiment. American Psychologist, Vol. 53, No. 7, pp. 709-727.

Milgram, S. (1974). Obedience to Authority. New York: Harper & Row.

Zimbardo, P. G. (1971). The power and pathology of imprisonment. Congressional Record. (Serial No. 15, October 25, 1971). Hearings before Subcommittee No. 3, of the Committee on the Judiciary, House of Representatives, Ninety-Second Congress, First Session on Corrections, Part II, Prisons, Prison Reform and Prisoner's Rights: California. Washington, DC: U.S. Government Printing Office.

Zimbardo, P. G. (1974). The detention and jailing of juveniles (Hearings before U. S. Senate Committee on the Judiciary Subcommittee to Investigate Juvenile Delinquency, 10, 11, 17, September, 1973). Washington, DC: U.S. Government Printing Office, 141-161.

Zimbardo, P. G., Haney, C., Banks, W. C., & Jaffe, D. (1973, April 8). The mind is a formidable jailer: A Pirandellian prison. The New York Times Magazine, Section 6, pp. 38, ff.

Zimbardo, P. G., Maslach, C., & Haney, C. (1999). Reflections on the Stanford Prison Experiment: Genesis, transformations, consequences. In T. Blass (Ed.), Obedience to Authority: Current Perspectives on the Milgram Paradigm. (pp. 193-237). Mahwah, NJ: Erlbaum.

American Psychological Association, June 8, 2004

The Stanford Prison Experiment 50 Years Later: A Conversation with Philip Zimbardo

Stanford Prison Experiment (Special Collections and University Archives, Stanford Libraries)

In April 1971, a seemingly innocuous ad appeared in the classifieds of the Palo Alto Times : Male college students needed for psychological study of prison life. $15 per day for 1-2 weeks. In no time, more than 70 students volunteered, and 24 were chosen. Thus began the Stanford Prison Experiment (SPE), conducted inside Jordan Hall on the Stanford campus. Originally scheduled to last two weeks, it was ended early over concerns regarding the behavior of both “prisoners” and “guards.” Still today, the SPE spikes enormous interest. Movies and documentaries have been made, books published, and studies produced about those six days. It’s clear today the research would never be allowed, but it was motivated by genuine concern over the ethical issues surrounding prisons, compliance with authority, and the evil humans have proved capable of. What was learned and at what cost? What is still being learned?

The Stanford Historical Society sponsors a look back at the controversial study with its leader, social psychologist Philip Zimbardo , Stanford Professor Emeritus of Psychology. Zimbardo is joined in conversation by Paul Costello who served as the chief communications officer for the School of Medicine for 17 years. He retired from Stanford in January 2021.

This program is organized by the Stanford Historical Society and co-sponsored by the Department of Psychology at Stanford University.

Additional resources

Watch video

Image credit: Stanford Prison Experiment (Special Collections and University Archives, Stanford Libraries)

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The Rarely-Told True Story of Zimbardo’s Prison Experiment

Goodness, evil, and the power that may cause both..

Posted July 20, 2013 | Reviewed by Jessica Schrader

You don’t need to have a background in psychology to know about Zimbardo’s prison experiment. Depicted in movies, television, and of course all introductory psych textbooks, the true story is rarely told of what really happened in that famous and controversial experiment. When such iconic studies become part of psychology lore, their true story often gets buried in overly simplistic interpretations. Worse still, as in the case of the equally famous Milgram obedience studies , the findings become grossly distorted. The truth behind these studies will be revealed to the first time to American audiences in September of 2013, with the publication of Gina Perry’s brilliant book, Behind the Shock Machine .

Inspired by her work, I decided to go back to the original source of some of the social psych studies I’ve written and taught about for years (actually, decades). Having read the same textbook summaries, ethical discussions, and secondary sources as thousands of psychology professors and students in the past 40 years since the actual study's first publication, I thought it was time to see what really transpired in those prison cells that Zimbardo and his team built to explore the “Interpersonal Dynamics in a Simulated Prison.” Published in 1973, this landmark study in the very first volume of the International Journal of Criminology and Penology, describes in academic, yet compelling, terms the frightening events that transpired over the course of the six-day experiment. From personality questionnaires to follow-up interviews, audio and video recordings, and the first-person experience of the “prison superintendent” (none other than Zimbardo), we learn much more than you can ever typically expect to find in your average psychology article.

Of course, it will be impossible to do justice to the entire article here, and for more personal accounts and images from the study, you can consult many online resources including Zimbardo’s own website devoted to the study. You may even have seen Professor Zimbardo on television talking about the study, or taken the video course he hosted. If you haven’t, here’s the study in a nutshell. 21 Stanford undergrads were recruited for a two-week study, divided randomly into 10 “prisoners,” and 11 ”guards.” They were placed into a prison setting, where the prisoners occupied cells, and the guards watched over them. After six days, the experiment had spun out of control as simulation turned into reality, necessitating the early release of some prisoners. Most introductory psych texts use this experiment to demonstrate the “power of the situation,” and the fact that ordinary college students could become sadistic monsters (i.e. the guards) in the space of just a few short days. That guards and prisoners were randomly assigned to condition was a key fact that added to the validity of the conclusion. Discussions of the study’s ethics today state that it could never be done now, but the fact is that Zimbardo did submit the study for approval to his institutional review board, and it met the criteria of the time (for more on the study's ethics, see Zimbardo, 1973).

First off, you should recognize that this was no hokey, clearly fake situation (a problem that seemed to plague the Milgram experiments). The authors took elaborate precautions to recreate a realistic prison environment, from the uniforms to the furniture in the cells to the food and the schedule. As a result, “within what was a surprisingly short time, we witnessed a sample of normal, healthy American college men fractionate into a group of prison guards who seemed to derive pleasure from insulting, threatning, humiliating and dehumanizing their peers…” The guards, who showed no signs of being sadistic types, were able to provoke emotional breakdowns in prisoners “selected precisely” for their emotional stability .

The guards entered the study thinking that it was the prisoners whose behavior was being studied. They received training from the Zimbardo acting out his superintendent role and an undergraduate research assistant who was the “warden.” The prisoners were told that they would be asked to take on a prisoner role but given no other information other than the fact that they would be “arrested” and brought into the prison. Neither group had very specific instructions because the point of the experiment was to see how they adapted to their respective roles.

The prisoners were “arrested” by actual police officers, “booked,” and then stripped and put in a cell yard until they received their uniforms. The uniforms were more like hospital gowns, and the men wore no clothing underneath so that they would feel “emasculated.” These steps intentionally created a feeling of deidentification or loss of their own personal identities. Perhaps the only difference between the study prisoners and real prisoners is that the Stanford prisoners were paid, and could escape if they requested to be released from the study.

The experimenters collected almost everything that transpired as “data,” leaving them with an enormous amount of information to sift through, code, and analyze. At the end of it all, Zimbardo believed that their data supports and validates the anecdotal evidence given by ex-convicts of life in prison. All the students involved experienced changes in moods including intense negative affect, an overall pessimistic outlook, and greater and greater declines in their self-esteem . Although the prisoners and guards could interact in any way they wished, the “characteristic nature of their encounters tended to be negative, hostile, affrontive, and deumanising.” Prisoners became passive and guards barked commands and hurled insults (they were prohibited from any form of physical violence). Four prisoners had to be released as early as the second day due to extreme emotional reactions, and one developed a psychosomatic rash soon later which also required that he be released. What was particularly telling is that when the experiment was halted, the prisoners took the news like any prison escapees would—with glee. The guards were angry and distressed.

Not everyone reacted equally badly to their roles, though, and some guards were “tough but fair.” For the most part, these differential reactions couldn’t be predicted by the personal tests that the participants completed at the start of the study. Some of the prisoners high on “authoritarianism” coped better with prison life, but other than this, there were few indications from the individual data about who would conform and who would rebel or be unable to continue in their role.

The guards resorted to various forms of harassment short of physical punishment . They called prisoners by number, not name, and hurled streams of insults at them. The evening shift was the harshest—it was then that guards gave out the most commands and were most insulting and controlling.

For their part, the prisoners essentially stopped communicating with each other about anything other than prison life (talk which occupied 90% of all their private conversations). They tried to set up a grievance committee, develop escape plans, wonder what the other prisoners were doing, and express concern about being placed in solitary confinement. The dehumanization they experienced from the guards carried over to their own interpersonal interactions, and soon they started deprecating each other. When they had the opportunity to talk to a priest, they referred to themselves by number, not name, showing just how far their deidentification had penetrated. Fortunately, all of these bad experiences, including their negative moods, bounced back to normal after the end of the study. Their depression and stress were restricted entirely to the situation, further reinforcing the idea that the “power” of the situation to overwhelm individual differences in mood and personality.

The study highlights what social psychologists continually drum into our heads, which is that the situation can and does shape our behaviors, thoughts, and feelings at even the most private of levels. Yet, as Zimbardo points out, if this were a true prison, people would forget the dehumanizing and deindividuating nature of the environment and attribute everyone’s behavior (guards and prisoners) to personal disposition. The prisoners would not be seen as antisocial by nature and the guards as little better. Not everyone reacts similarly to even this harsh of an environment, of course, as people learn different coping methods to help them adapt, but the range is much smaller than we would imagine.

To sum up , the Zimbardo study sheds the harshest light of perhaps any research ever done on the nature of power and its pervasive corruptive powers.

From the standpoint of the guards, the pathology of power led them to exert an “unprecedented degree of control” that was “self-aggrandising” and “self-perpetuating.” Prisoners in the real world want to wrest back some of this control by any means necessary, and so when released, they “will take action to establish and assert a sense of power.”

While in prison, though, the loss of personal identity and control led the prisoners to adopt the pathological prisoner syndrome, a reaction that took several forms of coping strategies. They went through stages from disbelief to rebellion; when these didn’t work, they tried to work the system (the “grievance committee”). When those efforts to gain control failed, it was every man for himself as each tried to find ways to preserve their own self-interests and identity. For some, this meant further rebellion and for others it meant becoming excessively obedient, even to the point of siding with the guards against intransigent prisoners.

Zimbardo and his co-authors hoped that the emotional and human price of the study would provide a model for improvements in the penal system as a whole. You might not agree with his conclusion, but it’s a thought-provoking one, so I’ll offer it here: “… since prisoners and guards are locked into a dynamic, symbiotic relationship which is destructive to their human nature, guards are also society’s prisoners.”

Follow me on Twitter @swhitbo for daily updates on psychology, health, and aging . Feel free to join my Facebook group, " Fulfillment at Any Age ," to discuss today's post, or to ask further questions about this posting.

Haney, C., Banks, C., & Zimbardo, P. (1973). Interpersonal dynamics in a simulated prison. International Journal of Criminology & Penology, 1(1), 69-97.

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. doi: 10.1016/0010-0277(72)90014-5

Susan Krauss Whitbourne, Ph.D. , is a Professor Emerita of Psychological and Brain Sciences at the University of Massachusetts Amherst. Her latest book is The Search for Fulfillment.

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Pre-written Conclusions

First Online: 09 August 2024

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Thibault Le Texier 2

The experiment’s conclusions have been written in advance according to nonacademic aims. Zimbardo designed his experiment from the outset as a demonstration of the toxicity of prisons. The experiment is directly connected to experiments that Zimbardo led in the 1960s, which reveals Zimbardo’s taste for spectacular experiments. At the time of the Stanford Prison Experiment, even though Zimbardo was not very involved in politics, his sympathies were heavily with prisoners.

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Philip G. Zimbardo and Greg White, The Stanford Prison Experiment Slide- Tape Show , produced by Philip G. Zimbardo, Inc., 1972, p. 1–2; an audio version is available here: “Slideshow narration, short version (80 slides),” July 13, 1972, ST-b01-f12, http://purl.stanford.edu/nx359zx3949; slightly later versions of this slideshow count 26 or 60 more photos, which mostly show the Attica revolt, but their text remains strictly the same: “Stanford prison experiment (106 slide version),” ST-b16-f01, https://purl.stanford.edu/gd264 gh4518; “Slideshow script for long version (136 slides),” ST-b09-f53, https:// purl.stanford.edu/ry243qv4755 , script which actually counts 140 photos.

Quiet Rage , documentary produced and directed by Ken Musen, written by Ken Musen and Philip G. Zimbardo, executive producer Philip G. Zimbardo, 1992.

Google Scholar

Here for example: https://exhibits.stanford.edu/spe/browse/photographs .

Philip G. Zimbardo and Greg White, The Stanford Prison Experiment Slide- Tape Show , op. cit. , p. 3.

Ibid., p. 4.

“The power of the situation. Interview with P. Zimbardo,” in Tamler Sommers, A Very Bad Wizard: Morality Behind the Curtain , San Francisco, Believer Books, 2009, p. 34.

Philip G. Zimbardo, The Lucifer Effect , op. cit. , p. 195 and 197. Zimbardo is probably referring to the exploratory experiments conducted by Milgram between the end of November and the beginning of December 1960, before finalizing his definitive protocols.

“News release,” August 16, 1971, ST-b11-f14, https://purl.stanford.edu/kn0 89qv2813 , p. 3.

Philip G. Zimbardo, “On the ethics of intervention in human psychological research: with special reference to the Stanford prison experiment,” Cognition , vol. 2, no 2, 1973, p. 248.

Article Google Scholar

Philip G. Zimbardo, W. Curtis Banks, Craig Haney and David Jaffe, “The mind is a formidable jailer: a Pirandellian prison,” op. cit. , p. 45.

Craig Haney and Philip G. Zimbardo, “Social roles and role-playing: observations from the Stanford prison study,” in Edwin P. Hollander and Raymond G. Hunt (eds.), Current Perspectives in Social Psychology , New York, Oxford University Press, 1976, p. 270.

Quoted in “‘Prison’ test halted: too brutal,” San Francisco Examiner , August 20, 1971.

Skype interview with Michael Lazarou, June 9, 2017.

Letter from Philip G. Zimbardo to Barbara Bridges, March 30, 1972, ST-b13-f4.

Letter from Philip G. Zimbardo to Peter C. Lewis, August 21, 1972, ST-b13-f4.

Craig Haney, W. Curtis Banks and Philip G. Zimbardo, “Interpersonal dynamics in a simulated prison,” International Journal of Criminology and Penology , vol. 1, 1973, p. 69–97.

“Articles of incorporation, Philip G. Zimbardo, Inc. 1972, circa 2000-circa 2002,” ST-b13-f22, signed on March 23, 1972 before a notary of Alameda County, Grace J. Knight.

“Recollections of a social psychologist’s career: an interview with Dr. Philip Zimbardo,” Journal of Social Behavior & Personality , vol. 14, no 1, 1999, p. 3.

Philip G. Zimbardo, “Phil Zimbardo remembers Neal Miller,” Biofeedback , vol. 38, no 3, 2010, p. 118.

Interview in Shelley Patnoe, A Narrative History of Experimental Social Psychology: The Lewin Tradition , New York, Springer, 1998, p. 119.

Philip G. Zimbardo and Herbert Barry, “Effects of caffeine and chlorpromazine on the sexual behavior of male rats,” Science , vol. 127, January 10, 1958, p. 85.

John B. WATSON, Behaviorism , New York, The People’s Institute Publishing Co., 1924, p. 94.

“Recollections of a social psychologist’s career: an interview with Dr. Philip Zimbardo,” op. cit. , p. 3.

Leon Festinger, A Theory of Cognitive Dissonance , Stanford, Stanford University Press, 1957, p. 5–6.

Book Google Scholar

“Recollections of a social psychologist’s career: an interview with Dr. Philip Zimbardo,” op. cit. , p. 8–9.

Cf. a summary of the results of his thesis: Philip G. Zimbardo, “Involvement and communication discrepancy as determinants of opinion conformity,” Journal of Abnormal and Social Psychology , vol. 60, no 1, 1960, p. 86–94.

Philip G. Zimbardo, The Cognitive Control of Motivation: The Consequences of Choice and Dissonance , Glenview, Scott, Foresman and Co., 1969.

Leon Festinger, Albert Pepitone and Theodore M. Newcomb, “Some consequences of de-individuation in a group,” Journal of Abnormal and Social Psychology , vol. 47, 1952, p. 382–389.

Philip G. Zimbardo, “The human choice: individuation, reason, and order versus deindividuation, impulse, and chaos,” in William J. Arnold and David Levine (eds.), Nebraska Symposium on Motivation, 1969 , Lincoln, University of Nebraska Press, 1970, p. 268.

Ibid., p. 270.

Ibid., p. 280–282.

Ibid., p. 277.

Telephone interview with Barry Schwartz, October 9, 2017.

Philip G. Zimbardo, “The human choice,” op. cit. , p. 282.

Cf. Tom Postmes and Russell Spears, “Deindividuation and antinormative behavior: a meta-analysis,” Psychological Bulletin , vol. 123, no 3, 1998, p. 238–259.

Cf. for example Philip G. Zimbardo, “Revisiting the Stanford prison experiment: a lesson in the power of situation,” The Chronicle of Higher Education , vol. 53, no 30, March 30, 2007, p. B6.

Philip G. Zimbardo, The Lucifer Effect , op. cit. , p. 301.

Gustave Le Bon, Psychology of Crowds , Paris, F. Alcan, 1895.

Floyd H. Allport, Social Psychology , Boston, Houghton Mifflin, 1924, p. 294.

Philip G. Zimbardo, “The human choice,” op. cit. , p. 251.

“Recollections of a social psychologist’s career: an interview with Dr. Philip Zimbardo,” op. cit. , p. 12.

Philip G. Zimbardo, “The human choice,” op. cit. , p. 250. 43.

Ibid., p. 240–247.

Philip G. Zimbardo, “Why Americans are growing more violent,” Sacramento Bee , April 27, 1969, p. F1.

“Human Subjects Committee interview with 1037, 5486 (tape #5),” https:// purl.stanford.edu/gj267jn4914 ; “Tape 8,” ST-b02-f08, https://stacks.stanford. edu/file/druid:vx097ry2810/Tape8.pdf.

“Diary of a vandalized car,” Time Magazine , February 28, 1969.

Philip G. Zimbardo, “A social-psychological analysis of vandalism: making sense of senseless violence,” ONR Technical Report Z-05 , U.S. Department of the Navy, Office of Naval Research, December 1970, p. 11–12.

Philip G. Zimbardo, “Vandalism: an act in search of a cause,” Bell Telephone Magazine , July–August 1972, p. 17.

Philip G. Zimbardo, “Mind control in Orwell’s Nineteen Eighty-Four : fictional concepts become operational realities in Jim Jones’s jungle experiment,” in Abbott Gleason, Jack Goldsmith and Martha C. Nussbaum (eds.), On Nineteen Eighty-Four: Orwell and Our Future , Princeton, Princeton University Press, 2005, p. 138–139.

“Psychologist says pressures of big-city life are transforming Americans into potential assassins,” New York Times , April 20, 1969.

“The Stanford prison experiment: still powerful after all these years,” Stanford Report , vol. 29, no 12, January 8, 1997, p. 8.

“NYU prof hits cops on arrest tactics,” New York Post , September 3, 1966. Zimbardo published this lecture the following year in a brand new popular science magazine: Philip G. Zimbardo, “The psychology of police confessions,” Psychology Today , vol. 1, no 2, June 1967, p. 17–20 and 25–27.

Philip G. Zimbardo, “Coercion and compliance: the psychology of police confessions,” in Robert Perrucci and Marc Pilisuk (eds.), The Triple Revolution Emerging: Social Problems in Depth , Boston, Little, Brown, 1971, p. 497.

Philip G. Zimbardo, “Toward a more perfect justice,” Psychology Today , vol. 1, no 3, July 1967, p. 45.

Letter from Philip G. Zimbardo to Robert Helmreich, copy to Elliot Aronson, February 14, 1972, ST-b11-f08.

Elliot Aronson and Robert Helmreich, “Closed environments: living in a sealed-off society,” in Elliot Aronson and Robert Helmreoch (eds.), Social Psychology , New York, Van Nostrand, 1973, p. 130–132, p. 132.

Philip G. Zimbardo, “Transforming experimental research into advocacy for social change,” op. cit. , p. 60.

“On 50 Years of giving psychology away: an interview with Philip Zimbardo,” Teaching of Psychology , vol. 36, 2009, p. 281.

“Recollections of a social psychologist’s career: an interview with Dr. Philip Zimbardo,” op. cit. , p. 13.

Howard Zinn, A People ’ s History of the United States: 1492-Present , New York, HarperCollins, 1999, p. 478.

“The power of the situation. Interview with P. Zimbardo,” op. cit. , p. 32.

Letter from Philip G. Zimbardo to Martin Luther King, Jr., April 27, 1967, ST 692-f56.

Philip G. Zimbardo, The Lucifer Effect , op. cit. , p. 493.

Robert P. Abelson and Philip G. Zimbardo, Canvassing for Peace: A Manual for Volunteers , Ann Arbor, Society for the Psychological Study of Social Issues, 1970.

Greg White, “Strike coordination new groups handle,” The Stanford Daily , vol. 157, no 52, May 7, 1970, p. 3.

Telephone interview with Greg White, December 21, 2017.

Philip G. Zimbardo, “The journey from the Bronx to Stanford to Abu Ghraib,” in Robert Levine, Aroldo Rodrigues and Lynnette Zelezny (eds.), Journeys in Social Psychology: Looking Back to Inspire the Future , New York, Psychology Press, 2008, p. 91 and 95.

Andrew Abbott, “Losing faith,” in Alan Sica and Stephen Park Turner (eds.), The Disobedient Generation: Social Theorists in the Sixties , Chicago, University of Chicago Press, 2005, p. 30–31.

On this assessment, cf. “John J. Schwartz,” interview with W. Abrams in April 2011, Stanford Historical Society Oral History Program Interviews, Department of Special Collections & University Archives, Stanford University Libraries, 2011, http://purl.stanford.edu/fb315jc8274 , p. 19–21; on May 68 at Stanford, cf. Irving Louis Horowitz and William H. Friedland, The Knowledge Factory: Student Power and Academic Politics in America , Carbondale, Southern Illinois University Press, 1972, p. 281–335.

Letter from Philip G. Zimbardo to Mark Janus, November 23, 1992, ST-b12-f03.

Timothy Leary, Jail Notes , preface by A. Ginsberg, New York, Douglas Book, 1970.

Timothy eary High Priest , New York, World Publishing, 1968, p. 207.

Charles Kadushin, The American Intellectual Elite , Boston, Little, Brown, 1974, p. 133 and 154.

Everett Carl Ladd and Seymour Martin Lipset, The Divided Academy: Professors and Politics , New York, McGraw-Hill, 1975, p. 57–58 and 121.

“Protecting Stanford’s freedom,” New York Times , January 11, 1972, www. nytimes.com/1972/01/11/archives/protecting-stanfords-freedom.html , p. 36.

Philip G. Zimbardo, “Transforming experimental research into advocacy for social change,” op. cit. , p. 62.

Cf. for example Philip G. Zimbardo, “Overcoming terror: is Washington terrorizing us more than Al Qaeda?,” Psychology Today , vol. 36, May–June 2003, p. 34–36, www.psychologytoday.com/articles/200307/overcoming- terror?collection=10069 .

His first report for the ONR dates from April 1970, a year and a half after his arrival. Cf. “The “truth” about false confessions, technical report,” with Christina Maslach, April 1970, report noONR-TR-Z-01.

Based on the various reports he submitted to the ONR between 1970 and 1975 then between 1979 and 1983 and registered from Z-01 to Z-17 and from Z-79-01 to Z-83-01.

Vannevar Bush, Modern Arms and Free Men: A Discussion of the Role of Science in Preserving Democracy , New York, Simon and Schuster, 1949, p. 6.

Robert M. Rosenzweig and Barbara Turlington, The Research Universities and their Patrons , Berkeley, University of California Press, 1982, p. 16–19 and 46–47.

Harvey M. Sapolsky, Science and the Navy: The History of the Office of Naval Research , Princeton, Princeton University Press, 1990, p. 40.

Ibid., p. 16; US Department of Labor, “History of federal minimum wage rates under the Fair Labor Standards Act , 1938-2009,” www.dol.gov/whd/ minwage/chart.htm .

Harvey Brooks, The Government of Science , Cambridge, MIT Press, 1968, p. 19–20; Seymour Melman, Pentagon Capitalism: The Political Economy of War , New York, McGraw-Hill, 1970, p. 90.

Cf. for example Irene L. Gendzier, Managing Political Change: Social Scientists and the Third World , Boulder, Westview Press, 1985; Christopher Simpson (dir.), Universities and Empire: Money and Politics in the Social Sciences during the Cold War , New York, New Press, 1998; Joy Rohde, Armed with Expertise: The Militarization of American Social Research during the Cold War , Ithaca, Cornell University Press, 2013.

Ellen Herman, The Romance of American Psychology: Political Culture in the Age of Experts , Berkeley, University of California Press, 1995, p. 126.

Ibid., p. 129.

John Darley, “Psychology and the Office of Naval Research: a decade of development,” American Psychologist , vol. 12, 1957, p. 305.

Rebecca S. Lowen, Creating the Cold War University: The Transformation of Stanford , Berkeley, University of California Press, 1997, p. 163 and 156–157.

Roger L. Geiger, Research and Relevant Knowledge: American Research Universities since World War II , New Brunswick, Transaction, 2004 [1993], p. 133.

Rebecca S. Lowen, Creating the Cold War University , op. cit. , p. 75.

David K. Allison, “U.S. Navy research and development since World War II,” in Merrill Roe Smith (dir.), Military Enterprise and Technological Change: Perspectives on the American Experience , Cambridge, MIT Press, 1985, p. 308–309. Confirming this refocus, an amendment to the 1970 military procurement law by Senator Fulbright requires that all research funded by Defense have a direct relationship with military purposes. According to its historian, the law had little impact on the ONR, which had already become for several years “an agency for applied research focused on the short-term needs of the Navy, and little more” (Harvey M. Sapolsky, Science and the Navy , op. cit. , p. 81).

Philip G. Zimbardo, “Stanford prison study points to share with M. L. (7/17/ 95),” ST-b11-f71, p. 3.

Philip G. Zimbardo, The Lucifer Effect , op. cit. , p. 27, 30 and 92.

Philip G. Zimbardo, “The Stanford prison experiment,” Psychology Today , blog, July 15, 2015, www.psychologytoday.com/blog/the-time-cure/201507/ the-stanford-prison-experiment .

“Tape 11,” ST-b11-f19, https://stacks.stanford.edu/file/druid:vx097ry2810/ Tape11.pdf, p. 8.

Telephone interview with Carlo Prescott, June 15, 2017.

“SWOPSI Project released report documents DOD research,” The Stanford Daily , vol. 159A, no 14, August 6, 1971.

“SWOPSI course reveals 119 defense contracts,” The Stanford Daily , vol. 160, no 6, October 4, 1971, p. 1; cf. “Prison experiment too realistic,” The Stanford Daily , vol. 160, no 12, October 12, 1971, p. 1.

Stanton A. Glantz et al., Department of Defense Sponsored Research at Stanford , vol. 1, Two Perceptions: The Investigator ’ s and the Sponsor ’ s , Stanford, SWOPSI, 1971, p. 285.

“Audio transcript-tape 2, orientation of guards,” https://stacks.stanford.edu/file/druid:vx097ry2810/Tape2.pdf.

Letter from David A. Baker to Philip G. Zimbardo (“Correctional Programs Specialist, Law Enforcement and Corrections Division, Department of the Navy, Bureau of Naval Personnel, Washington, D.C.”), July 30, 1974, AK-b01-f07, p. 1; “Prison slide show circa 1973-circa 1976,” ST-b12-f23.

James W. Newton and Philip G. Zimbardo (dir.), Corrections: Perspectives on Research, Policy and Impact , summary of the proceedings of a conference held on June 6 and 7, 1974 and organized by William Gaymon and Eugene Gloye, Office of Naval Research, ONR Technical Report Z-13 , p. 1–5.

Letter from Philip G. Zimbardo to Gus Avrakotos, December 5, 1972, ST-b13-f05.

Telephone interview with Gerald Gray, October 2, 2017; email exchanges with Jeffrey Kaye in October 2017; cf. Gerald Gray and Alessandra Zielinski, “Psychology and U.S. psychologists in torture and war in the Middle East,” Torture , vol. 16, 2006, p. 130.

Philip G. Zimbardo, “Commentary on the report of the American Psychological Association’s presidential task force on psychological ethics and national security (PENS Report),” July 19, 2006, www.scra27.org/files/5714/3774/ 8777/Zimbardo_Commentary_on_PENS_Report.pdf .

“The devil inside us all,” Times Higher Education , May 11, 2007, www. timeshighereducation.com/features/the-devil-inside-us-all/208926.article#survey- answer.

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Stanford Prison Experiment

Quiet Rage: The Stanford Prison Experiment

Philip G. Zimbardo

Philip Zimbardo was born on March 23, 1933 in New York City. He attended Brooklyn College where he earned a B.A. in 1954, triple majoring in psychology, sociology and anthropology. He then went on to earn his M.A. in 1955 and his Ph.D. in 1959 from Yale University, both in psychology.

He taught briefly at Yale before becoming a psychology professor at New York University, where he taught until 1967. After a year of teaching at Columbia University, he became a faculty member at Stanford University in 1968.

Philip Zimbardo is perhaps best known for the Stanford Prison Experiment, conducted in the basement of the Stanford University psychology department in 1971. The participants in the study were 24 male college students who were randomly assigned to act either as "guards" or "prisoners" in the mock prison.

The study was initially slated to last two weeks, but had to be terminated after just six days because of the extreme reactions and behaviors of the participants. The guards began displaying cruel and sadistic behavior toward the prisoners, while the prisoners became depressed and hopeless.

Since the prison experiment, Zimbardo has continued to conduct research on a variety of topics including shyness, cult behavior and heroism. In 2002, Zimbardo was elected president of the American Psychological Association. After more than 50 years of teaching, Zimbardo retired from Stanford in 2003 but gave his last "Exploring Human Nature" lecture on March 7, 2007.

Today, he continues to work as the director of an organization he founded called the Heroic Imagination Project. The organization promotes research, education and media initiatives designed to inspire ordinary people to act as heroes and agents of social change.

COMMENTS

Stanford Prison Experiment: Zimbardo's Famous Study
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 ...
8. Conclusion
Terminated on August 20, 1971. Our study was terminated on August 20, 1971. The next day, there was an alleged escape attempt at San Quentin. Prisoners in the Maximum Adjustment Center were released from their cells by Soledad brother George Jackson, who had smuggled a gun into the prison.
Conclusions to the Stanford Prison Experiment
Conclusions to the Stanford Prison Experiment. On August 20, 1971, Zimbardo announced the end of the experiment to the participants. According to Zimbardo's interpretation of the SPE, it demonstrated that the simulated-prison situation, rather than individual personality traits, caused the participants' behavior.
Stanford Prison Experiment: Zimbardo's Famous Study
In August of 1971, psychologist Philip Zimbardo and his colleagues created an experiment to determine the impacts of being a prisoner or prison guard. The Stanford Prison Experiment, also known as the Zimbardo Prison Experiment, went on to become one of the best-known studies in psychology's history —and one of the most controversial.
Stanford prison experiment
The Stanford prison experiment (SPE) was a psychological experiment conducted in August 1971.It was a two-week simulation of a prison environment that examined the effects of situational variables on participants' reactions and behaviors. Stanford University psychology professor Philip Zimbardo led the research team who administered the study.. Participants were recruited from the local ...
What the Stanford Prison Experiment Taught Us
PrisonExp.org. In August of 1971, Dr. Philip G. Zimbardo of Stanford University in California conducted what is widely considered one of the most influential experiments in social psychology to date. Made into a New York Times best seller in 2007 (The Lucifer Effect) and a major motion picture in 2015 (The Stanford Prison Experiment), the Stanford Prison Experiment has integrated itself not ...
How the Stanford Prison Experiment Worked
Zimbardo's conclusion was that we are not so much inherently "evil," but that we will commit heinous acts if encouraged to do so by systems that enable or encourage them. He took his results to the U.S. House of Representatives shortly after the experiment ended, testifying before a subcommittee on prison reform. His primary argument was that ...
The Stanford Prison Experiment: The Power of the Situation
In his subsequent Stanford experiment, Zimbardo would individualize the prisoners and deindividualized the guards. The prisoners wore a smock-like dress with a prisoner number on the front and back to individualize them. ... 5.4 Conclusion. The SPE is perhaps one of the two or three best known social behavioral science research studies. It is ...
Zimbardo prison study The Stanford prison experiment
The Stanford Prison Experiment, led by Philip Zimbardo in 1971, explored how social norms influence behavior. Normal students, randomly assigned as prisoners or guards, adopted their roles to alarming extents. Despite knowing it was an experiment, guards enforced harsh control, while prisoners exhibited severe emotional breakdowns, leading to ...
The Real Lesson of the Stanford Prison Experiment
June 12, 2015. A scene from "The Stanford Prison Experiment," a new movie inspired by the famous but widely misunderstood study. PHOTOGRAPH COURTESY SPENCER SHWETZ/SUNDANCE INSTITUTE. On the ...
Philip Zimbardo defends the Stanford Prison Experiment, his most ...
Zimbardo stated over and over the behavior seen in the experiment was the result of their own minds conforming to a situation. The new evidence suggests there was a lot more going on. The new ...
The Stanford Prison Experiment
Background and Objectives. In the 1960s and 70s, psychologist Philip Zimbardo conducted several notable social psychology experiments examining how social roles and situations can impact human behavior. Zimbardo designed the Stanford Prison Experiment in 1971 to explore the psychology of imprisoning people. He aimed to study how participants reacted to being assigned randomized roles of ...
Philip Zimbardo (Biography + Experiments)
Zimbardo designed the experiment to (1) give the guards the feeling of complete control and (2) rob the prisoners of their sense of reality, time, space, and self. ... Conclusions from the Stanford Prison Experiment. The study highlighted how certain social contexts can significantly influence or transform human behavior. Although all the ...
Inside the prison experiment that claimed to show the roots of evil
The experiment led Zimbardo to conclude that normal people could be transformed into sadistic tyrants or passive slaves, not because of any inherent personality flaws but through finding ...
Conformity to Social Roles as Investigated by Zimbardo
Zimbardo (1973) conducted an extremely controversial study on conformity to social roles, called the Stanford Prison Experiment. His aim was to examine whether people would conform to the social roles of a prison guard or prisoner, when placed in a mock prison environment. Furthermore, he also wanted to examine whether the behaviour displayed ...
Demonstrating the Power of Social Situations via a Simulated Prison
The lessons of the Stanford Prison Experiment have gone well beyond the classroom (Haney & Zimbardo, 1998). Zimbardo was invited to give testimony to a Congressional Committee investigating the causes of prison riots (Zimbardo, 1971), and to a Senate Judiciary Committee on crime and prisons focused on detention of juveniles (Zimbardo, 1974).
Stanford Prison Experiment
About the Stanford Prison Experiment. Carried out August 15-21, 1971 in the basement of Jordan Hall, the Stanford Prison Experiment set out to examine the psychological effects of authority and powerlessness in a prison environment. The study, led by psychology professor Philip G. Zimbardo, recruited Stanford students using a local newspaper ad.
The Story: An Overview of the Experiment
On a quiet Sunday morning in August, a Palo Alto, California, police car swept through the town picking up college students as part of a mass arrest for violation of Penal Codes 211, Armed Robbery, and Burglary, a 459 PC. The suspect was picked up at his home, charged, warned of his legal rights, spread-eagled against the police car, searched ...
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The Stanford Historical Society sponsors a look back at the controversial study with its leader, social psychologist Philip Zimbardo, Stanford Professor Emeritus of Psychology. Zimbardo is joined in conversation by Paul Costello who served as the chief communications officer for the School of Medicine for 17 years. He retired from Stanford in ...
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It can be argued that the conclusions that Professor Zimbardo and others have drawn from the Stanford Prison Experiment are not valid. Professor Zimbardo acknowleges that he was not merely an observer in the experiment but an active participant and in some cases it is clear he was influencing the direction the experiment went. For example ...
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If you haven't, here's the study in a nutshell. 21 Stanford undergrads were recruited for a two-week study, divided randomly into 10 "prisoners," and 11 "guards.". They were placed ...
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There are few studies in the history of psychology as renowned as the Stanford prison experiment (SPE) (Haney, Banks, & Zimbardo, 1973), and few psychologists as recognizable as the study's principal investigator, Philip Zimbardo.The SPE has influenced music, film, and art and has served as a testament to the power of "bad" systems and a counterbalance to "bad" person accounts of ...
Pre-written Conclusions
The conclusions that Zimbardo draws from this experiment are closer to barroom sociology than to psychological analysis: having simply observed a few passersby stripping and vandalizing an abandoned car in the Bronx, he does not hesitate to affirm that the root of the problem is the deindividuation fueled by "the greater sense of anonymity ...
Philip G. Zimbardo
Philip Zimbardo is perhaps best known for the Stanford Prison Experiment, conducted in the basement of the Stanford University psychology department in 1971. The participants in the study were 24 male college students who were randomly assigned to act either as "guards" or "prisoners" in the mock prison. The study was initially slated to last ...
Write A Term Paper On Zimbardo
In conclusion, this Zimbardo Prison Experiment was not worthwhile considering the amount of manipulation that took place which essentially invalidates the study as well as the studies results. To review, in this essay the main contributions making this study negligible are the ethical conduct, the role Zimbardo played in the experiment, the ...

Stanford Prison Experiment: Zimbardo’s Famous Study

Asserting Authority

Physical Punishment

Asserting Independence

Putting Down the Rebellion

Special Privileges

Consequences of the Rebellion

Prisoner #8612

A Visit from Parents

Catholic Priest

Prisoner #819

Back to Reality

An End to the Experiment

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

Critical Evaluation

Demand characteristics

Sample bias

Zimbardo’s conclusion may be wrong

Contributions to psychology

Contribution to prison policy

Evidence for situational factors

Evidence for an interactionist approach

Ethical Issues

Protection of Participants

Withdrawal

Discussion Questions

Frequently Asked Questions

Why did Zimbardo not stop the experiment?

What happened to the guards in the Stanford Prison Experiment?

What did Zimbardo want to find out?

What were the results of the Stanford Prison Experiment?

Further Information

The Stanford Prison Experiment

Purpose of the Stanford Prison Experiment

Participants in the Stanford Prison Experiment

Setting and Procedures

Results of the Stanford Prison Experiment

Impact of the Zimbardo Prison Experiment

Criticisms of the Stanford Prison Experiment

Ethical Issues

Why was Zimbardo's experiment unethical?

Lack of Generalizability

Lack of Realism

Recent Criticisms

What the Stanford Prison Experiment Taught Us

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The Takeaways

Author's Note: How the Stanford Prison Experiment Worked

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