stanford prison experiment rebellion

Stanford Prison Experiment: Zimbardo’s Famous Study

Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

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

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

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

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

On This Page:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Asserting Authority

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

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

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

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

Physical Punishment

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

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

Asserting Independence

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

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

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

Putting Down the Rebellion

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

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

Special Privileges

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

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

Consequences of the Rebellion

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

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

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

Prisoner #8612

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

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

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

A Visit from Parents

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

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

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

Catholic Priest

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

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

Prisoner #819

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

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

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

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

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

Back to Reality

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

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

An End to the Experiment

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Critical Evaluation

Ecological validity.

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

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

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

Demand characteristics

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

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

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

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

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

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

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

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

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

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

Sample bias

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

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

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

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

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

Zimbardo’s conclusion may be wrong

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

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

Contributions to psychology

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

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

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

Contribution to prison policy

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

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

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

The authors argue psychologists should reengage to:

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

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

Evidence for situational factors

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

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

Evidence for an interactionist approach

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

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

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

Ethical Issues

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

Protection of Participants

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

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

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

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

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

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

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

Withdrawal 

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

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

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

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

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

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

Discussion Questions

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

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

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

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

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

Frequently Asked Questions

What happened to prisoner 8612 after the experiment.

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

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

Why did Zimbardo not stop the experiment?

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

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

What happened to the guards in the Stanford Prison Experiment?

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

What did Zimbardo want to find out?

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

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

What were the results of the Stanford Prison Experiment?

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

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

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

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

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

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

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

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

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

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

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

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

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

Further Information

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

danny dutch

The stanford prison experiment: a dark exploration into the human psyche.

The Stanford Prison Experiment (SPE) remains one of the most controversial and frequently cited psychological studies in the history of behavioural science. Conducted in 1971 by psychologist Philip Zimbardo at Stanford University, the experiment sought to explore the psychological effects of perceived power, focusing on the struggle between prisoners and prison guards. It quickly spiralled out of control, leading to serious ethical concerns and raising troubling questions about human nature, authority, and morality.

Let's take a look at the background, methodology, results, and long-term implications of the Stanford Prison Experiment.

Background and Theoretical Foundations

In the late 1960s and early 1970s, American society was deeply divided by issues like civil rights, the Vietnam War, and distrust in government institutions.

These social fractures created an atmosphere ripe for exploring questions of authority, conformity, and rebellion.

Influenced by the atrocities of the Holocaust , the My Lai Massacre in Vietnam, and the increasingly heavy-handed nature of the police and military, social psychologists began probing how ordinary people could commit extreme acts of cruelty under certain conditions.

Philip Zimbardo, a psychology professor at Stanford University, was one such researcher. He had been particularly influenced by Stanley Milgram’s experiment in 1963, which demonstrated that people could be led to administer what they believed to be fatal electric shocks to others simply because they were ordered to by an authority figure. Zimbardo’s interest lay in understanding how systemic roles and structures, rather than direct orders, could cause individuals to abandon their personal morals and adopt abusive behaviour.

Zimbardo theorised that people were not inherently good or evil, but that situations could exert powerful forces on behaviour. The Stanford Prison Experiment was designed to test this hypothesis by simulating a prison environment and observing the ways in which ordinary individuals would adapt to roles of guards and prisoners.

The Experiment: Methodology and Setup

The SPE began on 14th August 1971, with 24 male college students from the Palo Alto area who had volunteered in response to an advertisement. These volunteers were screened to ensure they were psychologically stable and healthy, with no history of mental illness, criminal behaviour, or substance abuse. They were randomly assigned to play the role of either a prisoner or a guard in a simulated prison environment that was set up in the basement of the Stanford Psychology Department.

The basement was converted to resemble a prison as closely as possible. It included three small cells, each housing three prisoners, a guard’s room, a solitary confinement cell (called “The Hole”), and a warden’s office. There were hidden cameras and microphones placed in the cells and corridors, allowing Zimbardo and his team to observe the experiment continuously. The prisoners were given identical uniforms and referred to by numbers rather than names, dehumanising them and stripping them of their individuality. The guards wore khaki uniforms, reflective sunglasses to avoid eye contact, and carried batons, enhancing their authority and intimidation.

The prisoners were informed that they would be subjected to a series of conditions designed to simulate imprisonment, but not told the specific forms that these would take. The guards were given no explicit instructions on how to behave, apart from being told to maintain order and respect the rights of the prisoners, which gave them significant discretion in their actions. Zimbardo himself played the role of prison superintendent, which further blurred the lines between researcher and participant.

The experiment was originally planned to last two weeks, but it was abruptly terminated after just six days due to the extreme and disturbing behaviour exhibited by both guards and prisoners.

The Descent into Dehumanisation

From the outset, the participants quickly conformed to their assigned roles. The prisoners, who had been “arrested” from their homes by real police officers to add to the realism, were stripped, deloused, and dressed in smocks with chains placed around their ankles. This process was designed to create feelings of humiliation and helplessness. Meanwhile, the guards, imbued with their authority, soon began to exhibit increasingly authoritarian and abusive behaviours.

Within a day, the guards had adopted a regime of psychological harassment. They would wake the prisoners in the middle of the night for roll calls and forced physical exercises. They began to insult the prisoners, taunt them, and devise arbitrary rules to maintain control. One guard, referred to as “John Wayne” in later interviews, became particularly sadistic, adopting a southern accent and treating the prisoners with extreme cruelty.

As time progressed, the guards’ behaviour escalated. They enforced strict punishments for disobedience, such as confinement in “The Hole” for hours on end, forced public humiliations, and the withdrawal of basic privileges like food and bedding. Prisoners were made to clean toilets with their bare hands, and some were stripped naked to further degrade them.

The prisoners, in turn, began to exhibit signs of severe stress and trauma. By the second day, they attempted to rebel by barricading themselves in their cells, refusing to follow orders. In response, the guards retaliated with fire extinguishers, stripping the prisoners of their beds and clothing, and isolating the ringleaders. Over time, the prisoners became increasingly passive and submissive. Some prisoners had emotional breakdowns and had to be removed from the experiment early. One prisoner, identified only as “8612”, had to be released after just 36 hours when he began exhibiting signs of acute distress and uncontrollable crying.

Interestingly, the guards became more cohesive and bonded over their shared authority, while the prisoners became increasingly alienated from one another. This reflected the deindividuation and groupthink phenomena common in real-world prison environments, where people’s identities are suppressed, and group dynamics become a driving force in behaviour.

Ethical Concerns and the Termination of the Experiment

By the sixth day, the situation had deteriorated to such an extent that Zimbardo’s colleagues and outside observers began to voice serious concerns about the ethics of the experiment. Zimbardo himself, deeply immersed in his role as prison superintendent, failed to recognise how out of control the situation had become.

The experiment was finally ended when Christina Maslach, a graduate student who was Zimbardo’s girlfriend at the time, visited the site and was horrified by what she saw. She confronted Zimbardo, questioning the morality of continuing an experiment that was clearly causing harm to its participants. This external perspective was enough to break the spell, prompting Zimbardo to halt the experiment prematurely on 20th August 1971.

The decision to stop the experiment was a wake-up call for Zimbardo and his team. Although the guards and prisoners were simply role-playing, the lines between reality and simulation had blurred to such an extent that both groups had internalised their roles. The prisoners were showing signs of severe psychological trauma, while the guards had become sadistic in their exercise of power.

Criticisms and Legacy

The Stanford Prison Experiment has faced intense criticism over the years, particularly regarding its ethics and the validity of its findings. Many have argued that the experiment should never have been allowed to proceed, as the researchers failed to provide adequate protections for the well-being of participants. Critics also questioned whether Zimbardo’s dual role as researcher and prison superintendent created a conflict of interest that compromised the integrity of the experiment. By taking on an active role in the simulation, Zimbardo may have unintentionally encouraged or shaped the guards’ behaviour rather than merely observing it.

Another criticism is that the participants may have been influenced by demand characteristics—psychological cues that guide participants to behave in ways that align with what they believe the experimenter expects. Some of the guards later admitted that they had behaved in a sadistic manner because they believed that this was what Zimbardo wanted to observe.

Despite these criticisms, the Stanford Prison Experiment remains one of the most frequently cited studies in psychology. Its findings have been used to explain phenomena such as prison riots, police brutality, and even atrocities like those committed by American soldiers at Abu Ghraib prison in Iraq in 2004. Zimbardo himself has continued to explore the darker aspects of human nature, writing extensively about the conditions that lead ordinary people to commit acts of evil.

The SPE also led to significant changes in the ethical guidelines governing psychological research. Today, experiments that involve such extreme manipulation of participants’ psychological states are heavily scrutinised, with institutional review boards required to ensure the safety and well-being of participants.

A Cautionary Tale

The Stanford Prison Experiment stands as a chilling reminder of the power that social roles, authority, and situational pressures can have on human behaviour. While its ethical shortcomings are undeniable, it continues to offer valuable insights into the potential for ordinary people to commit extraordinary acts of cruelty when placed in positions of power. The SPE serves as a cautionary tale, urging us to consider how systems, rather than individuals, can create environments where immorality flourishes.

Though conducted over 50 years ago, the Stanford Prison Experiment remains a critical point of reference for debates on human nature, ethical research practices, and the often-frightening effects of unchecked authority.

Recent Posts

Sheriff Buford Pusser; Survivor Of Seven Stabbings And Eight Shootings.

Robert McGee, As A 14-Year-Old He Was Scalped By Native Americans.

The Cokeville Bombing: A Community Shaken

• History & Society
• Science & Tech
• Biographies
• Animals & Nature
• Geography & Travel
• Arts & Culture
• Games & Quizzes
• On This Day
• One Good Fact
• New Articles
• Lifestyles & Social Issues
• Philosophy & Religion
• Politics, Law & Government
• World History
• Health & Medicine
• Browse Biographies
• Birds, Reptiles & Other Vertebrates
• Bugs, Mollusks & Other Invertebrates
• Environment
• Fossils & Geologic Time
• Entertainment & Pop Culture
• Sports & Recreation
• Visual Arts
• Demystified
• Image Galleries
• Infographics
• Top Questions
• Britannica Kids
• Saving Earth
• Space Next 50
• Student Center

What the Stanford Prison Experiment Taught Us

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.

Learn More About This Topic

• How does a situation cause violent behavior?
• What is social psychology?

Know a mentally disturbed person who doesn’t think much of others? Make sure you apply the right epithet.

Recommended from the web

• Visit the Stanford Prison Experiment official website

The Stanford Prison Experiment: The Power of the Situation

• First Online: 20 January 2024

Cite this chapter

• Harry Perlstadt   ORCID: orcid.org/0000-0002-0233-0463 3  

Part of the book series: Clinical Sociology: Research and Practice ((CSRP))

333 Accesses

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

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

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Subscribe and save.

• Get 10 units per month
• Download Article/Chapter or eBook
• 1 Unit = 1 Article or 1 Chapter
• Cancel anytime
• Available as PDF
• Read on any device
• Instant download
• Own it forever
• Available as EPUB and PDF
• Durable hardcover edition
• Dispatched in 3 to 5 business days
• Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

Alexander, M. (2001, August 22). Thirty years later, Stanford Prison Experiment lives on. Stanford Report . Accessed April 22, 2022, from https://news.stanford.edu/news/2001/august22/prison2-822.html?msclkid=7d17df2ec26f11ec8086da6bf715d359

Amdur, R. J. (2006). Provisions for data monitoring. In E. A. Bankert, & J. R. Amdur (Eds.), Institutional review board: Management and function , 2nd edition (pp. 160–165). Jones & Bartlet

Google Scholar  

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

Article   Google Scholar  

Blau, P. M. (1964). Exchange and power in social life . Wiley.

Farkas, M. A. (2000). A typology of correctional officers. International Journal of Offender Therapy and Comparative Criminology, 44 (4), 431–449. https://doi.org/10.1177/0306624X00444003

Festinger, L., Pepitone, A., & Newcombe, T. (1952). Some consequences of deindividuation in a group. Journal of Abnormal and Social Psychology, 47 , 382–389.

French, J. R. P., & Raven, B. (1959). The bases of social power. In D. Cartwright (Ed.), Studies in social power (pp. 150–167). Institute for Social Research.

Frohnmayer, D. (2004, November 30). “Situational ethics, social deception, and lessons of machiavelli” Judge learned hand award Luncheon Oregon chapter of the American Jewish Committee Tuesday . http://president.uoregon.edu/speeches/situationalethics.shtml

Goffman, E. (1961). Asylums. Essays on the social situation of mental patients and other inmates . Doubleday Anchor. http://www.diligio.com/goffman.htm

Gross, B. (2008, Winter/December). Prison violence: Does brutality come with the badge? The Forensic Examiner . http://www.theforensicexaminer.com/archive/winter08/6/

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

Lovibond, S. H., Mithiran, & Adams, W. G. (1979). Effects of three experimental prison environments on the behaviour of non-convict volunteer subjects. Australian Psychologist, 14 (3), 273–285.

Maslach, C. (1971). The “truth” about false confessions. The Journal of Personality and Social Psychology, 20 (2), 141–146. https://doi.org/10.1037/h0031675

Maslach, C. (1974). Social and personal bases of individuation. Journal of Personality and Social Psychology, 29 (3), 411–425. https://doi.org/10.1037/h0036031

Maslach, C., Marshall, G., & Zimbardo, P. G. (1972). Hypnotic control of peripheral skin temperature: A case report. Psychophysiology, 9 (6), 600–605. https://doi.org/10.1111/j.1469-8986.1972.tb00769.x

Morgan, A. H., Lovibond, S. H., & Adams, W. G. (1979). Comments on S. H. Lovibond, Mithiran, & W. G. Adams: “The effects of three experimental prison environments on the behaviour of non-convict volunteer subjects”. Australian Psychologist, 14 (3), 273–287.

NHLBI. (2008). National Heart Lung and Blood Institute. Data and safety monitoring policy . http://www.nhlbi.nih.gov/funding/policies/dsmpolicy.htm

O’Toole, K. (1997, January 8). The Stanford prison experiment: Still powerful after all these years. Stanford report . Stanford University News Service. http://www.stanford.edu/news/gif/snewshd.gif

Prescott, C. (2005, April 28). The lie of the Stanford prison experiment. The Stanford Daily .

Sawyer, K. D. (2021). George Jackson, 50 years later . Accessed January 18, 2022, from https://sfbayview.com/2021/08/george-jackson-50-years-later/?msclkid=4afbd2c7c26b11eca875b013aedf20b3

Schaufeli, W. B., & Peeters, M. C. W. (2000). Job stress and burnout among correctional officers: A literature review. International Journal of Stress Management, 7 (1), 19–48. https://doi.org/10.1023/A:1009514731657

Schlesinger Report. (2004). Final report of the independent panel to review Department of Defense Detention Operations . http://news.bbc.co.uk/nol/shared/bsp/hi/pdfs/24_08_04_abughraibreport.pdf

SPE Website. (n.d.). Stanford Prison Experiment Website. The story: An overview of the experiment . Accessed February 28, 2022, from https:// www.prisonexp.org/the-story

Weber, M. (1947). The theory of social and economic organization . Oxford University Press.

Zimbardo, P. (1969). The human choice: Individuation, reason and order versus deindividuation, impulse, and chaos. In W. J. Arnold & D. Levine (Eds.), Nebraska Symposium on Motivation (Vol. 17, pp. 237–307). University of Nebraska Press.

Zimbardo, P. G. (1970). The human choice: Individuation, reason, and order versus deindividuation, impulse, and chaos. In W. J. Arnold & D. Levine (Eds.), 1969 Nebraska symposium on motivation (pp. 237–307). University of Nebraska Press. Accessed January 19, 2022, from https://stacks.stanford.edu/file/gk002bt7757/gk002bt7757.pdf

Zimbardo, P. G. (1971a). Application for institutional approval of research involving human subjects . August, 1971. Available at: http://www.prisonexp.org/pdf/humansubjects.pdf . Accessed December 1, 2023.

Zimbardo, P. G. (1971b). Prison life study: General information sheet . August, 1971. Available at: http://www.prisonexp.org/pdf/geninfo.pdf . Accessed December 1, 2023.

Zimbardo, P. G. (2008). The lucifer effect: Understanding how good people turn evil . Random House.

Zimbardo, P. G., Haney, C., Banks, W. C., & Jaffe, D. (1972). Stanford prison experiment . Philip G. Zimbardo, Inc. (Tape recording).

Zimbardo, P. G., Haney, C., Banks, W. C., & Jaffe, D. (1972, April 8). The mind is a formidable jailer: A Pirandellian prison. New York Times Magazine, Section 6, 36, ff.

Zimbardo, P. G., Marshall, G., & Maslach, C. (1971). Liberating behavior from time-bound control: Expanding the present through hypnosis. Journal of Applied Social Psychology, 1 (4), 305–323. https://doi.org/10.1111/j.1559-1816.1971.tb00369.x

Zimbardo, P. G., Marshall, C., White, G., & Maslach, C. (1973). Objective assessment of hypnotically induced time distortion. Science, 181 (4096), 282–284.

Zimbardo, P. G., Maslach, C., & Haney, C. (2000). Chapter 11: 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). Lawrence Erlbaum Associates.

Download references

Acknowledgments

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

Author information

Authors and affiliations.

(emeritus) Department of Sociology, Michigan State University, East Lansing, MI, USA

Harry Perlstadt

You can also search for this author in PubMed   Google Scholar

Rights and permissions

Reprints and permissions

Copyright information

© 2023 The Author(s), under exclusive license to Springer Nature Switzerland AG

About this chapter

Perlstadt, H. (2023). The Stanford Prison Experiment: The Power of the Situation. In: Assessing Social Science Research Ethics and Integrity. Clinical Sociology: Research and Practice. Springer, Cham. https://doi.org/10.1007/978-3-031-34538-8_8

Download citation

DOI : https://doi.org/10.1007/978-3-031-34538-8_8

Published : 20 January 2024

Publisher Name : Springer, Cham

Print ISBN : 978-3-031-34537-1

Online ISBN : 978-3-031-34538-8

eBook Packages : Social Sciences Social Sciences (R0)

Share this chapter

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

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

Provided by the Springer Nature SharedIt content-sharing initiative

• Publish with us

Policies and ethics

• Find a journal
• Track your research

Stanford Prison Experiment: Zimbardo’s Famous Social Psychology Study

The Stanford prison experiment was a social psychology study which demonstrated the horrors people can inflict on one another.

The Stanford prison experiment was run to find out how people would react to being made a prisoner or prison guard.

The psychologist Philip Zimbardo, who led the Stanford prison experiment, thought ordinary, healthy people would come to behave cruelly, like prison guards, if they were put in that situation, even if it was against their personality.

It has since become a classic study, studied by generations of psychology students and recently coming under a lot of criticism.

What was the Stanford prison experiment about?

The Stanford prison experiment asks timeless questions about human nature, like what makes a person evil?

Can a good person commit evil acts?

If so, what can make people cross the line?

Is there some set-point which when crossed unleashes the evil?

Or is it something about the situations in which people are placed that determines our behaviour?

The famous ‘Stanford Prison Experiment’ – argues a strong case for the power of the situation (Zimbardo, 1971).

Not only that but the experiment has also inspired a novel, two films, countless TV programs, re-enactments and even a band.

More on that later, first the experiment.

The procedure of the Stanford prison experiment

The idea was simple: to see how ordinary men, chosen to be the most healthy and ‘normal’ would respond to a radical change to their normal roles in life.

Half were to become prison guards, the other half their prisoners. In this experiment there were no half-measures, for it to be effective it had to closely approximate the real experience of prisoners and guards.

These participants in the Stanford prison experiment were in for the ride of their lives.

‘Prisoners’ were ‘arrested’ by a police car with sirens wailing while they were out going about their everyday business.

Then they were fingerprinted, blindfolded and put in a cell, then stripped naked, searched, deloused, given a uniform, a number and had a chain placed around one foot.

The other participants were made into guards who wore uniforms and were given clubs.

A prison was mocked up in the basement of a Stanford University building.

And so the Stanford prison experiment began.

Rebellion crushed

All was quiet until the second day when the ‘prisoners’ rebelled against their incarceration.

The guard’s retaliation was swift and brutal.

Guards stripped the prisoners naked, removed the beds from the prison, placed the rebellion’s ringleader in solitary confinement and began harassing all the ‘prisoners’.

Soon the ‘prisoners’ began behaving with blind obedience towards the prison guards.

After only a few day’s realistic role-playing participants reported it felt as though their old identities had been erased.

They had become their numbers.

So too had the ‘guards’ taken on their roles – taunting and abusing their prisoners.

Even the lead researcher, Philip Zimbardo, admits he became submerged in his role as the ‘prison superintendent’.

In fact, Zimbardo believes the most powerful result of the Stanford prison experiment was his own transformation into a rigid institutional figure, more concerned with his prison’s security than the welfare of his participants.

Other members of the experimental team became engrossed in their new role.

Craig Haney, like Zimbardo, explained he became completely engaged in the day-to-day crises they were facing in running the ‘prison’ and forgot about the aim of the Stanford prison experiment.

Playing the roles

It was only when one of his colleagues intervened that the Stanford prison experiment was finally stopped.

In total it only lasted six of the planned 14 days.

Young men previously found to be pacifists were, in their roles as guards, humiliating and physically assaulting the ‘prisoners’ – some even reported enjoying it.

The ‘prisoners’, meanwhile, quickly began to show classic signs of emotional breakdown.

Five had to leave the ‘prison’ even before the experiment was prematurely terminated.

The psychological explanation for the participant’s behaviour was that they were taking on the social roles assigned to them.

This included adopting the implicit social norms associated with those roles: guards should be authoritarian and abuse prisoners while prisoners should become servile and take their punishment.

Inevitably the Stanford prison experiment has attracted criticism for being unethical, involving a small sample size, lack of ecological validity and so on.

Despite this it’s hard to deny that the experiment provides important insights in to human behaviour, perhaps helping to explain the abuses that occurred in situations like the Abu Ghraib Prison.

Conclusions of the Stanford prison experiment

The Stanford prison experiment showed how people are ready to conform to the roles they are given and expected to play.

They lost their identity within the group, taking the cue from what other people were doing.

The situation of the prison turned guards into sadists and reduced their sense of identity and personality responsibility.

The prisoners were also surprised how much it changed their behaviour.

Even assertive types became submissive and weak when placed in the role of a prisoner in the Stanford prison experiment.

In this sense it showed that the situation was more powerful in guiding people’s behaviour than their personality.

Is the Stanford prison experiment realistic?

Does this Stanford prison experiment mirror what occurs in real prisons?

Writing in Inside Rikers: Stories from the World’s Largest Penal Colony , Jennifer Wynn interviews prison guards from New York City’s largest penal colony, Rikers Island.

One captain explained that guards easily become used to the level of violence inflicted on inmates – it’s part of the job and they soon become immune.

Some can’t understand how they become different people at work.

Levels of violence against prisoners were so bad in one unit, called the ‘Central Punitive Segregation Unit’ of Rikers’, that almost a dozen guards were officially charged with assaulting inmates in 1995.

Eventually the inmates won $1.6 million dollars in compensation.

This is just one example.

Criticism of the Stanford prison experiment

Other the years, many criticism have been thrown at the Stanford prison experiment, including:

• The guards later claimed they were acting in the Stanford prison experiment: psychologists refer to this as the demand characteristics of the study.
• The prisoners and guards were playing a role so you cannot generalise to real life. Different factors may affect people’s behaviour in real life. The Stanford prison experiment’s prison itself was not that realistic and people knew they were not in prison.
• Because of its ethics, the study could not be conducted nowadays. It would not pass any standard psychological ethics committees. For example, participants did not agree to be ‘arrested’ at their homes.
• Subsequent studies have cast doubt on the validity of the Stanford prison experiment, suggesting that participants ‘faked’ their behaviour and tried to help the experimenters ( Texier, 2019 ).

Popular culture and the Stanford Prison Experiment

The study is now so well-known it has crossed over into popular culture. It has inspired a novel, Das Experiment by Mario Giordano, which was later filmed , and a new movie by the writer of the Usual Suspects is slated for filming.

The experiment has also been covered or recreated in countless TV shows, most notably on the BBC .

Not only this, but the experiment has even inspired the name of a band.

‘Stanford Prison Experiment’ released their first eponymously titled album in 1994, following up a year later with ‘The Gato Hunch’.

What other psychology study can say it’s got a band named after it?

→ This post is part of a series on the best social psychology experiments :

• Halo Effect : Definition And How It Affects Our Perception
• Cognitive Dissonance : How and Why We Lie to Ourselves
• Robbers Cave Experiment : How Group Conflicts Develop
• Stanford Prison Experiment: Zimbardo’s Famous Social Psychology Study
• Milgram Experiment : Explaining Obedience to Authority
• False Consensus Effect : What It Is And Why It Happens
• Social Identity Theory And The Minimal Group Paradigm
• Negotiation : 2 Psychological Strategies That Matter Most
• Bystander Effect And The Diffusion Of Responsibility
• Asch Conformity Experiment : The Power Of Social Pressure

Author: Dr Jeremy Dean

Psychologist, Jeremy Dean, PhD is the founder and author of PsyBlog. He holds a doctorate in psychology from University College London and two other advanced degrees in psychology. He has been writing about scientific research on PsyBlog since 2004. View all posts by Dr Jeremy Dean

Join the free PsyBlog mailing list. No spam, ever.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Stanford Prison Experiment

• Quiet Rage: The Stanford Prison Experiment

Stanford Prison Experiment slideshow, 106 slide version : Three prisoners starting rebellion. 41, Slide

Bibliography.

Pardon Our Interruption

As you were browsing something about your browser made us think you were a bot. There are a few reasons this might happen:

• You've disabled JavaScript in your web browser.
• You're a power user moving through this website with super-human speed.
• You've disabled cookies in your web browser.
• A third-party browser plugin, such as Ghostery or NoScript, is preventing JavaScript from running. Additional information is available in this support article .

To regain access, please make sure that cookies and JavaScript are enabled before reloading the page.

• The Disturbing Stanford Prison Experiment
• The Most Evil Experiments by the US Govt
• Japanese WWII Unit 731
• Scientists Who Paid with Their Lives
• Disgusting Experiments on Human Beings
• History's Most Brutal Human Experiments
• The 'Little Albert' Experiment
• WWII Japanese Experiments on US Airmen
• The Horrific Tuskegee Syphilis Experiments
• The Contained Attempts at Biosphere 2
• Crazy Medical Experiments That Worked
• Creating Utopia in America
• Attempts to Create a Frankenstein
• Barbaric Studies on Human Beings
• Experiments on Unknowing US Soldiers
• They Took Babies Away from Their Mothers
• Using Orphaned Babies to Train Expecting Moms
• Could You Have Become a Nazi? Yes, Probably
• Crazy Animal Experimentation Through History

• PrisonExp.org

The Day-By-Day Breakdown Of What Happened During The Stanford Prison Experiment

In 1971, professor Philip Zimbardo put together one of the most intriguing and famous psychology experiments  ever: the Stanford Prison Experiment, designed to study the effects of incarceration on prisoners and guards. Using an advertisement to recruit college-aged men in the area for a one-of-a-kind study, Zimbardo and his team hoped to remove volunteers predisposed to mental illness and those with existing records from their experiment. Nonetheless, the Stanford Prison Experiment brought out those qualities in its participants.

Originally meant to be a two-week examination of the imbalance of power and the Lucifer Effect - the ability of ordinary people to engage in evil acts - the entire experiment began unraveling from day one: August 14, 1971. While the faux prisoners were housed in a converted basement of Stanford University's psychology department, they experienced the same degradation, erasure, and humiliation felt by real inmates. Alternatively, the make-believe guards embraced their power as if it was real by forcing their prisoners to humiliate themselves and creating rules to boost their own egos.

While nothing on par with true prison stories  from penitentiaries around the world happened, the Stanford Prison Experiment quickly spiraled out of control and ended on August 20, 1971. It proved how easily men could be swayed to commit evil acts when provided the power to do so and to what lengths an individual would go in order to reclaim their identity and autonomy.

Day One: The Participants Are Arrested And Jailed

The Palo Alto police arrested nine young men at their residences and charged them with burglary and armed robbery in front of visibly shocked onlookers. These volunteers, cast in the role of prisoners, later arrived at the Palo Alto police department for regulation bookings . They were fingerprinted and read their Miranda rights.

Meanwhile, in the basement of the Stanford Psychology Department's building, three young men randomly assigned as prison guards prepped for the arrival of the inmates. They donned their chosen uniforms but were  not given any specific instructions on how to be guards.

The  inmates were brought down  to the makeshift prison. It was a single corridor in the basement of Stanford University's psychology building re-purposed to be the only location the prisoners could walk around outside of their cells. It was renamed "The Yard." Along the corridor, some rooms had their doors removed and replaced with bars and numbers to serve as cells. Opposite the cell was previously a closet, which was renamed "The Hole" and used as solitary confinement. 

Each prisoner stripped off their clothes, received a delousing spray, and changed into a prison shift with a number sewn on it. In lieu of shaving their hair, they covered their hair with stocking caps.

At this time, some of the guards on duty mocked the genitals  of prisoners, something they were not instructed or prompted to do. With the rules of the prison presented to them, the inmates retired to their cells for the rest of the first day of the experiment.

Day Two: The Prisoners Rebel

The prisoners were only referred to as identification numbers and confined to their small cells. After a full day and a 2:30 am wake-up call of whistles and clanging from guards, many of the inmates rebelled . In an effort to reassert their independence, prisoners refused to leave their cells to eat in The Yard. The men ripped off their inmate numbers, took off their stocking caps, and hurled insults and obscenities at their guards.

In response, the night shift guards remained at work with the morning shift, and three more guards came in from a pool of remaining volunteers for the experiment. The guards sprayed fire extinguishers at the prisoners, forcing them to back away from their cell doors. The guards entered and reasserted control. They removed all of the prisoners' clothes and mattresses, and instigators received time in The Hole.

The guards attempted to dissuade any further rebellions through the use of psychological warfare.

Day Three: The Guards Divide The Prisoners Based On Behavior During The Rebellion

In order to cut off further acts of disobedience, the guards granted prisoners who had minimal roles in the rebellion with special privileges as a reward . The three spent time in a cell where they received clothing, beds, and food denied to the rest of the jail population.

After an estimated 12 hours of time in the "good" cell, the three prisoners went back into the cells that lacked beds and switched places with a new set of inmates, sowing the seeds of mistrust among the formerly aligned prisoners.

The guards used their power to humiliate the inmates by having them count off and do pushups arbitrarily and by  rescinding access to the bathrooms , forcing the inmates to answer the call of nature with a bucket in their cells. 

During all of this, prisoner #8612 began to show signs of a mental breakdown . While all participants received assurances at the beginning that they could leave at any time, prisoner #8612 instead received an offer of less guard harassment in exchange for becoming an informant. His condition deteriorated further; he began to scream in a fit of uncontrollable rage, and after Zimbardo realized he may truly be suffering, #8612 was released.

Day Four: The Prisoners Divide Among Themselves

After witnessing the guards divide prisoners based on rebellious behavior, the inmates distanced themselves from one another. The instigators of the riot believed some of the other prisoners were snitches while others saw the rebellion organizers as a threat to the status quo. No one wanted to have their sleeping cots or clothes removed again, nor did they want to spend time in The Hole.

Prisoner #819 began crying in his cell and displaying other symptoms of distress. A real priest with experience working in prisons was brought in, but #819 declined to speak with him; instead, he asked for a medical doctor.  Zimbardo removed the young man from the experiment. While he left his cell and undressed from his prison garbs, the guards cajoled the remaining inmates into loud chants decrying #819 as a bad prisoner.

After reassurances of his actual identity from Zimbardo, #819 agreed to leave.

Day Five: Outside Parties Grow Concerned About The Psychological Effects Of The Punishments 

On the fifth day, friends and family members of the inmates were brought in for visitations . Zimbardo and the guards forced visitors to sign in and wait long periods of time to see their loved ones in order to simulate a real prison. The warden spent time with each set of family members discussing the situation of their respective inmate. Only two visitors could see any one prisoner for ten minutes at a time while a guard watched.

Some parents asked about their children's well-being and whether they had enough to eat, but quickly backed down when Zimbardo questioned the resilience and toughness of their sons. Many parents left with plans to contact a lawyer  to gain early release for their children.

After the visiting hours ended, a rumor arose claiming inmate #8612 was set to return and liberate the remaining prisoners. But rather than investigate the source of the rumor, Zimbardo and the guards concerned themselves more with protecting the prison and ensuring none of the prisoners could escape.

During this time, Zimbardo's colleague Gordon Bower arrived to check on the experiment and questioned the independent variable in play. Zimbardo disturbed even himself by reacting to Bower's question with anger. Even he had fallen into thinking like a prison superintendent rather than a social psychologist. 

Furthermore, a recent PhD recipient,  Christina Maslach , visited the prison to question the inmates and guards. But due to the inhumane conditions the prisoners lived in and the sadistic treatment by the guards, she spoke out about the morality of the study, prompting Zimbardo to consider ending it.

Day Six: All Participants Are Released Early

Due to outrage from his colleague Christina Maslach and the increasing violence exhibited by the guards, Zimbardo ended the study more than a week early .

On the sixth day, Zimbardo gathered the participants and let them know that the experiment was really over and they could go home. Zimbardo met with all the guards, then with all the prisoners, before everyone came together to discuss the experience. Even the participants released early from the experiment came back to go over their feelings and thoughts.

• No category

Stanford prison experiment

Related documents.

Add this document to collection(s)

You can add this document to your study collection(s)

Add this document to saved

You can add this document to your saved list

Suggest us how to improve StudyLib

(For complaints, use another form )

Input it if you want to receive answer

The Ugly Truth About The Stanford Prison Experiment

The Stanford Prison Experiment is one of psychology's most notorious, and disturbingly telling, explorations of the relationship between self-identity and social role. Conducted at Stanford University in California in 1971, and funded by the U.S Office of Naval Research, the experiment involved the participants' complete immersion into the roles of prisoners and prison guards. The basement of Stanford University, as described in Simply Psychology , was kitted out to look exactly like a prison , complete with cells, shower rooms, cafeteria, and the like. The researcher in charge, Dr. Philip Zimbardo (who played the warden), conducted psychological evaluations of would-be participants, and recruited the most stable young men to be prisoners and guards. Which would be the dominant mode of behavior: dispositional, or situational? In other words, would the participants act like themselves, or would they merely behave according to the social norms expected of their role?

What started out as a rather interesting, if extreme, LARP transformed into an horrific display of humiliation, brutality, and subservience. What was originally planned to be a two-week study was cut short at six days. In that time, the guards adopted cruel and abusive behavior, such as forcing prisoners to clean toilets with their bare hands, placing them in solitary confinement, chaining them in place, and stripping them naked. Prisoners donned their fabricated roles and staged a full-blown rebellion. They wept as they used their IDs rather than their names; several suffered a complete emotional breakdown.

Loss of self, loss of dignity, loss of empathy

Out of all the potential explanations for the behavior of the participants, two terms stand out: deindividuation and learned helplessness. Deindividuation is defined as the loss of self in lieu of group norms, especially in the case of highly stereotyped roles like the "tough but fair" law enforcement officer. This can account for the guards believing that they were just doing their jobs. Learned helplessness can help explain why the prisoners eventually gave up: Their efforts to resist produced no meaningful impact. 

When asked to explain their behavior, some of the guards — only a couple of whom self-identified as naturally assertive — simply said that authority "felt fun." The more dependent the prisoners grew, the more the guards resented them. The prisoners became objects to revile rather than persons in need of rehabilitation. One guard, after the fact, said that he was shocked at what he became capable of when placed in a position where he had to "act" a part.

The Stanford Prison Experiment has been criticized for obvious ethical reasons, though during the study , only one researcher out of 50 objected to what was happening. The study has also been called out for lacking ecological validity and population validity. The results of the study, no matter how enlightening, can't be readily applied to a non-experimental setting, and the population itself (American males) doesn't represent an inclusive group of cultures, ethnicities, and genders.