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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.

Abu Ghraib: The Real Stanford Prison Experiment

Extended commentary by Peter Kinderman .

The pictures above and below were taken at Abu Ghraib Prison in Iraq during 2003-2004 and outline how some of the prisoners were mistreated by US military personnel.

The Stanford Prison Experiment (1971) was a psychological experiment conducted by Professor Philip Zimbardo, whereby he wanted to observe the psychological effects of being a prisoner / prison guard. This study is famous for the highly unethical methodology which involved the ‘prison guards’ essentially subjecting the ‘prisoners’ to psychological torture – which was encouraged by Zimbardo as the experimenter.

The experiment was stopped after only 6 days, and some people have attributed the extreme role playing by the ‘prison guards’ as being caused by the situation and the power of authority, rather than the individual personalities of the participants playing the guards.

There are several reports of rape by US soldiers of the prisoners, and some accounts where other soldiers took photos. There are also accounts of sexual abuse using various objects, and many accounts of torture including strappado hanging.

Additionally, the New York Times reported in 2005, further cases of abuse including;

• Urinating on detainees
• Jumping on a detainees already injured leg, so forcefully that it was unable to heal properly afterwards
• Pouring phosphoric acid on detainees
• Sodomization of detainees with a baton
• Typing rope to detainees legs or genitals and dragging them across the floor.

17 soldiers and officers were removed from duty, and 11 soldiers were charged with offences including, battery, dereliction of duty, maltreatment and aggravated assault. Other personnel were dishonourably discharged from duty, sent to military prison, repremanded for dereliction of duty or demoted.

Zimbardo was an expert witness at the Abu Ghraib trials presumably due to his involvement in the Stanford Prison Experiment, which has some similarities to the abuse of power seen at Abu Ghraib Prison.

Could it be argued that it was the situation that caused the US army to act in such a way, or do you think it was a personality trait of the soldiers involved?

To see footage and interviews with the participants in Zimbardos Stanford Prison experiment click here .

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What a widely attacked experiment got right on the harmful effects of prisons

Assistant Professor of Sociology, University of Toronto

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The Stanford Prison Experiment is one of the few scientific studies to enter the public consciousness through mainstream news , documentaries , popular books , a TED talk and a major motion picture .

Recently, it has been making headlines in a very bad way.

In 1971, Stanford University psychology professor Philip Zimbardo sought to evaluate the prison’s impact on human behavior . He randomly assigned normal, healthy, emotionally stable male college students (without criminal records) to be “prisoners” or “guards” in a fake prison.

Within six days, Zimbardo ended the experiment. The “guards” were torturing the “prisoners,” and the “prisoners” were rebelling or experiencing psychological breakdown.

In news articles, the Stanford experiment has been “debunked” and “exposed as a fraud.” Its findings have been declared “very wrong” and “ fake .” It has been further criticized for experimenter interference, faked behaviour from participants and for research design problems, among other things.

These serious critiques have generated much discussion in academic circles and in news articles about what, if anything, we can learn from the experiment.

And yet, as someone who studies prisons, I’m struck by how much the Stanford Prison Experiment got right. A wealth of other research suggests prisons have serious detrimental effects on prisoners and prison workers alike.

What the research says

Living and working in prison is extremely stressful and demoralizing .

Some people are better at repelling these effects than others. Even so, prisoners and prison workers suffer from high rates of depression, anxiety, suicide, PTSD and other devastating conditions. For many prisoners, these conditions continue after prison and can be worsened by the transition into the free world .

We have long known that prisons are damaging places for both prisoners and prison workers. In his 1956 book, Society of Captives , Princeton sociology professor Gresham Sykes explained that incarceration deeply injured prisoners’ dignity and self-concept. He also described how prison officers became “corrupted” by the prison environment with its contradictory imperatives, impossible-to-enforce rules and necessary compromises.

In the 60 years since Sykes’ book, research in diverse prison settings has confirmed and expanded upon many of his findings.

The role of prison design

These insights extend beyond contemporary prisons in the United States. Prisons in Norway , Sweden and Denmark , known for their humaneness, also cause harm.

Indeed, smart designs can lessen , but not destroy, the prison’s negative impacts. But since the 1970s , in many Western countries, the main goal when designing prisons has been containment and security, not prisoners’ physical and mental health.

Popping up in the U.S. in the 1980s and 1990s, supermaximum security prisons (Supermaxes), which contain prisoners in solitary confinement in small concrete cells for 23 hours a day , are a particularly harmful design.

Read more: Broken system: Why is a quarter of Canada's prison population Indigenous?

Prisoners react differently to these Supermax prison regimes. Some are able to withstand the conditions, others break down within hours of their arrival. We do not yet fully understand why people react differently, but we do know that Supermax prisons have an array of negative impacts on prisoners’ mental health including hallucinations, self-harm and permanent psychological damage .

Not just prisoners

Prison staff are also affected. The history of American imprisonment is also filled with examples of people with good intentions becoming “corrupted” by the prison.

Pennsylvania’s Eastern State Penitentiary opened in 1829. Progressive Philadelphia penal reformers designed Eastern to be more humane than other prisons, with prisoners’ physical and mental health in mind. They implemented a routine — combining work, education, mentorship and outdoor exercise — to benefit both prisoners and society. Finally, they sought to protect prisoners’ identities so they could reenter society without stigma.

Within five years of the prison’s opening, however, the penal reformers, now prison administrators, had betrayed their humanitarian goals.

They bent the rules , out of necessity or convenience, so the prison functioned smoothly. In the process, they sacrificed the regime’s humanitarian and prisoner-focused elements.

Eastern’s administrators authorized torture , including what we now call waterboarding, held misbehaving prisoners after their sentences had expired until they apologized and justified these actions as beneficial to prisoners.

These gaps between theory and practice, including the use of torture punishments, were common at other American prisons in the 19th century and into the 20th. Other penal reformers–turned-administrators engaged in similar malfeasance despite their apparently genuine commitment to humanitarian values.

The situation was even more dire at prisons that were explicitly designed to be punitive and lacked Eastern’s humanitarian motivations .

Beyond the Stanford experiment

Even including these past failures, modern prisons rarely devolve as quickly and decidedly into a den of overt torture and serious mental breakdown as seen in the “Stanford Prison.”

It does happen — the Abu Ghraib torture scandal and the retaking of Attica Prison following the 1971 riot are graphic illustrations of how prison can unleash the worst of human nature with terrible consequences — but such extreme cases remain rare. Prisons’ negative effects are typically less dramatic and do less to capture the public imagination.

There is something about prisons that is damaging. But what is it?

Even the most humanely designed prisons have negative effects on the people living and working inside. And that is the deep truth we are still seeking to understand and the Stanford Prison Experiment effectively illustrates.

• Mental health
• Criminal justice
• Prison reform
• Criminal justice reform
• Prison violence
• Waterboarding
• Solitary confinement
• Prison guards

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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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Stanford Prison Experiment

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

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

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

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

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

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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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Time to Dismiss the Stanford Prison Experiment?

By  Greg Toppo

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Stanford University

Since its inception nearly 47 years ago, the Stanford Prison Experiment has become a kind of grim psychological touchstone, an object lesson in humans' hidden ability to act sadistically -- or submissively -- as social conditions permit.

Along with Yale University researcher Stanley Milgram’s 1960s experiments on human cruelty, the August 1971 experiment has captured Americans’ imaginations for nearly half a century. It is a long-standing staple of psychology and social science textbooks and has been invoked to explain horrors as wide-ranging as the Holocaust, the My Lai massacre and the Abu Ghraib prisoner-torture scandal.

But new interviews with participants and reconsideration of archival records are shedding new light on the experiment, questioning a few of its bedrock assumptions about human behavior.

Perhaps most significantly, one of the “prisoners” now says his actions have long been misunderstood.

For the experiment, Stanford University psychology professor Philip Zimbardo built a three-cell mock “Stanford County Jail” in the basement of the university’s psychology building. His researchers housed nine “prisoners” and hired nine “guards,” all of whom had answered a classified ad looking for participants for a two-week study on prison life.

But just 36 hours into the experiment, prisoner Douglas Korpi found himself in lockdown, sealed into a closet repurposed as a makeshift solitary confinement room. He soon experienced what has been described as a mental breakdown.

It was one of the most visceral moments from the experiment, and it was caught on audiotape , with Korpi screaming, “I'm so fucked-up inside. I feel really fucked-up inside. You don't know -- I gotta go, to a doctor. Anything! I mean, Jesus Christ, I’m burning up inside, don’t you know? I can't stay in there. I'm fucked-up! I don't know how to explain it. I'm all fucked-up inside! And I want out! And I want out now! ”

Korpi now says his episode was less a psychotic break than a manipulation so he could go home and study.

“Anybody who is a clinician would know that I was faking,” he told author Ben Blum in a rare interview last year, part of a lengthy feature in the online publication Medium . Now a forensic psychologist in Oakland, Korpi characterized his outburst as “more hysterical than psychotic.”

Actually, he screamed not because of abusive guards but because he was worried about not getting access to textbooks during his “prison” stay so he could cram for the Graduate Record Examination.

Korpi said he took the $15-per-day job as a prisoner because he thought he’d have time “to sit around by myself and study for my GREs.” The prison study, scheduled to last two weeks, lasted only six days after Zimbardo’s girlfriend, Christina Maslach (now his wife of many years), persuaded him to shut it down.

But when Korpi, who was scheduled to take the GRE just after the study concluded, asked for his books, guards refused. After unsuccessfully faking a stomachache, he faked the breakdown.

The admission is similar to one he gave the Los Angeles Times in 2004, when he said, "Zimbardo thought I was losing it."

Looking back on the experience, he told Blum he actually enjoyed himself most of the time, including during a brief prisoner “rebellion.”

“The rebellion was fun,” he said. “There were no repercussions. We knew [the guards] couldn’t hurt us, they couldn’t hit us. They were white college kids just like us, so it was a very safe situation.”

He was, however, shocked that he couldn’t leave of his own free will, remembering that the guards were “really escalating the game by saying that I can’t leave. They’re stepping to a new level. I was just like, ‘Oh my God.’”

In an interview, Zimbardo told Blum that the subjects “really believed they can’t get out,” but said they’d signed informed-consent forms that included an explicit “safe” phrase: “I quit the experiment.” Saying the phrase, he said, would earn an exit from the experiment.

Blum notes that the forms, dated August 1971 and available online at Zimbardo’s website , contain no mention of the phrase “I quit the experiment.” They do, however, consent to “a loss of privacy,” among other conditions. The forms note that subjects were expected to participate “for the full duration of the study,” and that they’d only be released for reasons of health “deemed adequate by the medical advisers to the research project or for other reasons deemed appropriate” by Zimbardo.

Blum’s revelations come weeks after the release of Story of a Lie , a new book by French academic and filmmaker Thibault Le Texier, who examined newly released documents from Zimbardo’s Stanford archives. He calls the experiment “one of the greatest scientific deceptions of the 20th century.”

In a tweet posted last week, University of California, Davis, psychology professor Simine Vazire wrote, “We must stop celebrating this work. It’s anti-scientific. Get it out of textbooks.”

In a statement issued Monday, Howard Kurtzman, acting executive director for science at American Psychological Association, said Blum’s Medium article “raises important questions about the Stanford Prison Experiment, many of which have been raised before.” He gave credit to Zimbardo for speaking to Blum and said the researcher “has responded to these questions over the years.”

Psychology textbook authors who address the study “would be well advised to place it in context, including the controversies around its methods and what it teaches us about the importance of institutional review boards, peer review and replicability,” Kurtzman said.

Dave Eshelman, a Stanford “guard” who earned the nickname John Wayne for his imaginative cruelty, told Blum he saw the experiment “as a kind of an improv exercise” that he wanted to perfect “by creating this despicable guard persona.” He has long maintained that he developed the cruel character after watching the movie Cool Hand Luke .

Eshelman said he tapped into his own experiences in a brutal fraternity hazing a few months earlier. Nearly half a century later, he recalled feeling “like I had accomplished something good because I had contributed in some way to the understanding of human nature.”

In a 2011 interview published in the Stanford alumni magazine , Eshelman said, “I set out with a definite plan in mind, to try to force the action, force something to happen, so that the researchers would have something to work with. After all, what could they possibly learn from guys sitting around like it was a country club?”

In a way, Eshelman said, he was running his own experiment within an experiment, each day trying to do something “more outrageous” than the day before. He often wondered “how much abuse will these people take before they say, ‘knock it off’? But the other guards didn't stop me. They seemed to join in. They were taking my lead. Not a single guard said, ‘I don't think we should do this.’”

Another guard, John Mark, told the alumni magazine that Zimbardo “went out of his way to create tension,” with strategies like forced sleep deprivation. He said Zimbardo “knew what he wanted and then tried to shape the experiment -- by how it was constructed, and how it played out -- to fit the conclusion that he had already worked out.”

Mark said Zimbardo wanted to show that middle-class young people “will turn on each other just because they're given a role and given power.” But he said that hypothesis was “a real stretch. I don't think the actual events match up with the bold headline. I never did, and I haven't changed my opinion.”

Zimbardo, who would later testify about human behavior in the wake of the bloody 1971 Attica Prison uprising in upstate New York, did not immediately respond to a request for an interview. Nor did Craig W. Haney, a psychology professor at UC Santa Cruz who was a graduate student of Zimbardo's in 1971 and a principal researcher on the prison experiment.

Haney has said he and his fellow researchers “weren't sure anything was going to happen” when the experiment began. “I remember at one point asking, ‘What if they just sit around playing guitar for two weeks? What the hell are we going to do then?’”

Speaking to the alumni magazine in 2011, he said the experiment’s most enduring finding may be how quickly “we get used to things that are shocking one day and a week later become matter-of-fact.”

He recalled that while preparing to move the prisoners, researchers realized that the subjects would figure out they were in the Stanford psychology building, not in an actual prison. So they put paper bags over their heads. “The first time I saw that, it was shocking,” Haney recalled. “By the next day we're putting bags on their heads and not thinking about it. That happens all the time in real correctional facilities.”

Haney said the experiment showed him the effects of dehumanization on incarcerated people.

“I try to talk to prisoners about what their lives are really like, and I don't think I would have come to that kind of empathy had I not seen what I saw at Stanford,” he said. “If someone had said that in six days you can take 10 healthy college kids, in good health and at the peak of resilience, and break them down by subjecting them to things that are commonplace and relatively mild by the standards of real prisons -- I'm not sure I would have believed it if I hadn't seen it happen.”

Blum’s new interviews are only the latest to take a magnifying glass to Zimbardo’s research. In 2001, British researchers who recreated the experiment suggested that guards acted tyrannically not because of the “toxic combination of groups and power,” but because of something more complex.

The turning point in Zimbardo’s experiment, they maintained, was when he stepped in as “prison superintendent” and told prisoners they couldn’t leave the study. Researchers Stephen Reicher and S. Alexander Haslam said this revelation disoriented the prisoners, who “ceased to support each other against the guards.” The tight group collapsed, allowing “tyrannical guards to prevail.”

In their modified re-enactment, dubbed the BBC Prison Study , prisoners actually challenged the guards’ authority, leading to a collapse of the prisoner-guard system. The participants then decided to continue the experiment as a “self-governing and self-disciplining ‘commune,’” but this too fell apart a day later, paving the way for the emergence of “a new tyranny” in the little lockup. In one key moment, a participant looked into the lens of a video camera and told researchers, “We’re having a military takeover of the regime that’s been put in place yesterday.” He demanded “full military uniforms” and vowed, “We’re going to run this prison the way it should have been run from day one.”

The researchers concluded that when people can’t create a social system that works, they’ll “more readily accept extreme solutions proposed by others” and allow an authoritarian ideology to take hold.

More recently, in 2007, Western Kentucky University psychologists Thomas Carnahan and Sam McFarland placed ads in several university newspapers, offering to pay volunteers for a “psychological study of prison life,” as Zimbardo’s ad had in 1971. They also invited another group to participate simply in a “psychological study,” without any mention of prison life.

Then they tested the respondents and found that those who replied to the “prison life” ad scored higher on measures of authoritarianism, narcissism, Machiavellianism, social dominance and “abuse-related dispositions of aggressiveness.” They also scored lower on measures of empathy and altruism, suggesting that the Stanford subjects may have showed up in August 1971 with traits of cruelty that not all of us necessarily possess.

“I’m a believer that the situation can lead people to do cruel things,” McFarland said in an interview. But he said a kind of selection bias may have played a part in the Stanford results. For one thing, Zimbardo openly sought subjects for a two-week, immersive experiment on prison life. “It just seems intuitively strong to me that some people would be more disposed to volunteer for such an experiment than would others,” he said.

McFarland, now retired, got the opportunity in 2006 to interview Sergeant Joseph Darby, the former U.S. Army reservist who blew the whistle on the Abu Ghraib prison scandal and who has publicly criticized U.S. military leadership at the facility. Asked by McFarland if most servicemen and women would have tortured and humiliated prisoners if they’d been stationed at Abu Ghraib, Darby flatly said: No.

“I could have taken any seven other soldiers from that unit and put them in the same situation and they would have acted honorably and professionally and performed their duties,” he said, according to an audio recording of the interview.

Eshelman, the guard who modeled his behavior on Cool Hand Luke , said he later regretted the mental abuse he inflicted. But when revelations about Abu Ghraib came to light, he said, his first reaction was, “This is so familiar to me. I knew exactly what was going on. I could picture myself in the middle of that and watching it spin out of control. When you have little or no supervision as to what you're doing, and no one steps in and says, ‘Hey, you can't do this,’ things just keep escalating.”

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• Personality

Individual Differences in the Stanford Prison Experiment

The stanford prison experiment did not show situations overpower personality.

Posted September 10, 2013

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The Stanford Prison experiment (SPE) is one of the most famous, or indeed infamous, studies in the history of psychology. The dramatic and horrifying result of the SPE have been used to draw rather sweeping conclusions about human nature and the psychology of evil. For example, the SPE supposedly illustrates the power of an abusive situation to induce good people to do evil things. In particular, Phil Zimbardo has argued that the study shows that strong situational forces can override individual differences in personality and moral values so that the latter count for very little. Indeed he has even claimed that virtually anybody at all who was put into a situation where they had power over others, such as guards have over prisoners, would act in a tyrannical and abusive way. Furthermore, the results of the SPE have been applied to prisoner abuse in Abu Ghraib. The fact that the SPE has had the influence it has had is all the more remarkable considering the obvious limitations of the study, such as its small sample size and the ad hoc way in which the experiment was conducted. Closer examination shows that the design of the SPE did not provide an adequate test of the role of individual differences in a simulated prison, and that no satisfactory account of the individual differences in behaviour shown by participants has been offered. Therefore, the popularly accepted conclusion that the SPE shows that “situational power triumphs over individual power in certain contexts” (Zimbardo, 2007, p. x) is quite unfounded.

Dispositions vs. situations - opposed or complementary?

The details of the SPE are fairly well-known and are explained in detail on Zimbardo’s website . Susan Krauss Whitbourne also provides a nice accessible summary of the study on her blog . When the study was first published, the stated rationale was to critique the “dispositional hypothesis” of why prison life is so deplorable (Haney, Banks, & Zimbardo, 1973). Briefly, the “dispositional hypothesis” supposedly blames the “nature” of the people who administer the prison system (e.g. the guards) and the “nature” of the people who populate it (the prisoners). That is, when guards act in a brutal manner it is because they are brutal people. Alternatively, prisoners are seen as naturally aggressive people unable to control their impulses, and therefore repressive measures are needed to control them. According to Haney et al., this dispositional hypothesis has been invoked both by those who defend the status quo (poor conditions in prisons are due to evil prisoners) and by critics of the system (poor conditions in prisons are due to sadistic guards). Supposedly, such simplistic explanations draw attention away from the complex social, economic, and political causes that really underlie this deplorable situation, and which are too difficult to change without radical social upheaval. A few years ago, a research paper proposed that self-selection might have influenced the outcomes of the SPE, because the sort of people who would willingly volunteer for a study on prison life might have distinctive personality traits that might predispose them to abusive behaviour (Carnahan & McFarland, 2007). [1] Haney and Zimbardo (2009) responded to this by attacking the influence of what they call “persistent dispositionalism” in psychology – “explaining context-driven socially problematic behavior in largely individualistic, trait-based terms, no matter how much evidence has been amassed to the contrary”.

The alternative hypothesis that Haney et al. present is a “situationist” one, which is the claim that powerful and oppressive social situational forces, such as occur in a prison, over-ride individual differences in personality and moral values, and induce ordinary decent people to act in abhorrent ways. Haney et al. (1973) attacked the idea that prisoner abuse is due to “bad seeds” and alternatively suggested that the prison system consists instead of “bad soil” that can corrupt anyone. More recently, Zimbardo has used the metaphor of “good apples” placed into “a very bad barrel” to explain why apparently good people have done evil things.

Situations can reveal personality

Note the apparent dichotomy here. A person’s behaviour in a situation such as a mock prison or even a real one is supposed to be due either to their internal dispositions or the external features of the situation, but not both. I think this a false dichotomy that has led to extreme and unfounded conclusions. Furthermore, it appears to be based on a straw man argument. When Haney et al. (1973) originally discussed the “dispositional hypothesis” they did not cite any references to show that this is a real hypothesis taken seriously by any genuine scholars. Perhaps certain naïve laypeople believe in it, but whether actual social scientists and psychologists do is not clear. Similarly, when Haney and Zimbardo (2009) attack “persistent dispositionalism” they seem to invoke a decades-old misconception that personality psychologists believe that behaviour can be understood primarily as a function of a person’s traits without serious consideration of the context of the person’s behaviour. On the contrary, personality psychologists have long maintained that a person’s behaviour is a function of both the features of the person and the features of the situation, not just one or the other. That is, a personality psychologist might argue that people generally make choices about how to behave in order to meet their needs within the constraints and opportunities inherent in particular situations. [2]

Regarding the SPE in particular, the authors who argued that self-selection could have influenced the SPE’s outcome responded to Haney and Zimbardo’s criticism that they supposedly preferred “dispositionalist” explanations over situational ones, by affirming that they did not at all deny that features of the situation had a powerful influence on the behaviour of the participants (McFarland & Carnahan, 2009). What they were arguing was that traits might influence a person’s decision to participate in such a situation in the first place. Furthermore, they also argued that being in such a situation with people with similar personality traits would tend to amplify whatever tendencies one already had to be abusive. However, Zimbardo (2007) has argued for a more extreme situationist view, claiming that “a large body of evidence in social psychology supports the concept that situational power triumphs over individual power in certain contexts” and that bad situations can cause “good” people to do “evil” things. However an alternative view of the power of situations is that they provide opportunities that can reveal rather than suppress individual differences ( Krueger , 2008). That is, put two different people with different desires in the same situation, and they may respond in accordance with their personal preferences, within whatever constraints are imposed by the demands of the situation. Let’s examine the actual findings of the SPE and see which view of situational power finds more support.

What really went down at Stanford

The SPE study sample consisted of 21 [3] men who had been selected from a large pool of 75 volunteers based on psychological assessments to ensure their mental stability and lack of criminal history. One day prior to the study these 21 were assessed on ten different personality trait tests and then randomly assigned to the role of guard or prisoner – 11 to the former, 10 to the latter. On the whole it seems, the guards were pretty mean, and the prisoners became demoralised by their situation, and five of the latter had such adverse psychological reactions that they had to be released early. So far, sounds like a big win for the situationist account right? Participants acted the way they did based on their situationally defined roles, so the situation had a strong influence on their behaviour. However, I don’t think anyone is actually denying that situations influence behaviour. Zimbardo’s claim is that “situational power triumphs over individual power.” If this was the case, then we would have expected there to have been little or no variation in the way participants behaved in their respective roles as prisoners or guards. Did this really happen though?

According to the original report by Haney et al. there actually were notable individual differences in how the prisoners and guards behaved.

“Some guards were tough but fair (“played by the rules”), some went far beyond their roles to engage in creative cruelty and harassment, while a few were passive and rarely instigated any coercive control over the prisoners” (p. 81).

Apparently about a third of the guards (so about 3 or 4) were actively cruel, while those described as “passive” by Haney et al. have been described elsewhere as “good guards from the prisoner’s point of view since they did them small favors and were friendly”. Furthermore, although five prisoners broke down under the stress of being abused, the other five were more resilient .

Image courtesy of Sura Nualpradid at FreeDigitalPhotos.net

A role for personality traits after all?

The original report by Haney et al. does acknowledge that personality traits could moderate the effect of social situational variables, allaying or intensifying the latters’ effects. That is, individual differences in participants could influence how they respond to the perceived demands of their assigned role. When discussing the limitations of their study they even go so far as to admit that they could not adequately test whether a dispositional or a situational account provides a better explanation of their results and state that “We cannot say that personality differences do not have an important effect on behavior in situations such as the one reported here.” They acknowledge that a stronger test would involve comparing two conditions where participants were pre-selected for having more extreme personality traits. I suppose one way to do this would be to set up two mock prisons for comparison, one featuring people selected for above-average kindness and compassion, the other one populated only with narcissists and psychopaths . If there were no differences in the behaviour shown in the two conditions (!) this would provide strong evidence that personality traits are not an important influence on behaviour in such a situation. However, they lacked the resources to perform such an experiment, which (hardly surprisingly) has not been done to this day.

In their more recent article though, Haney and Zimbardo (2009) summarily dismissed the role of individual differences, arguing that the precautions and controls they used in their original study were sufficient to lay to rest “any trait-based explanations of our findings.” Specifically, participants were assessed on a number of personality traits and found to score within the normal range for the general population. Additionally, guards and prisoners did not differ on any of these traits. And finally, these personality measures did not predict variations in behaviour within either the prisoner group or the guard group. Supposedly, these precautions should be enough to settle the matter for good.

Strong Situations and Weak Arguments

On its face, such an assertion that the results from a single study of 21 people can permanently lay to rest “any” trait-based explanations seems to me like a breathtakingly bold dismissal that flies in the face of usual scientific practice. Such a small single study like this would normally be considered by most scientists just the beginning of enquiry into the matter not the end of it. Haney and Zimbardo offer no explanation of why individual differences occurred in people who were exposed to the same situation, yet claim that they have enough evidence to dismiss “any” trait-based explanation at all based on their statistical analysis of 21 people. Let’s examine the merits of their “precautions and controls.”

The first argument is that participants did not differ from the general population on their personality traits, and were therefore a fair sample of “normal” individuals. Eight of these measures comprised the Comrey Personality scales. According to a critique by McFarland and Carnahan (2009) none of these traits have ever been linked to abusive and aggressive behaviour. If this is correct, they would have been of no use in assessing whether the participants were “normal” with respect to their propensity to be abusive in a situation where they held power over others. The other two traits measured were authoritarianism and Machiavellianism (the propensity to manipulate others for one’s own gain), which would appear to be theoretically relevant to abusive behaviour. The original report by Haney et al. is actually silent on how their participants compared to the normal population on these measures. For some reason that is not made clear, the researchers used a non-standard scoring method for Machiavellianism that makes comparisons with the general population not possible. Carnahan and McFarland (2007) pointed out that participants actually did score higher on authoritarianism than the general population and their scores were actually comparable to those found in a study of actual prisoners in San Quentin. Haney and Zimbardo argued that the actual difference from the norm was fairly small, so whether it was enough to contribute to the actual behaviour of participants in their study was a moot point. Still, the matter has hardly been “laid to rest.”

The second argument is that participants assigned to the prisoner and guard roles did not differ significantly on their personality traits. Apart from the minuscule sample size involved, which I will address shortly, I am tempted to respond “So, what?” Prisoners and guards were effectively in two different situations with differing opportunities and faced different challenges. For example, some of the guards disturbed the prisoners’ sleep by banging on their cell doors. The prisoners obviously did not have the opportunity to reciprocate this treatment, because the guards went home at the end of their shifts. So the prisoners could not engage in such abusive behaviour even if they had felt inclined to do so, because the opportunity was simply not there. As I have argued earlier, personality theorists propose that individual differences are relevant to how people respond to their circumstances, not that individual differences somehow allow people to transcend these circumstances and behave however they feel like.

Haney and Zimbardo’s third argument is that the behaviour of individuals within their respective roles of prisoner or guard could not be predicted from their personality scores. They do not deny that there were individual differences in behaviour, just that they could not predict them. I think this is their weakest argument of all. Remember that there were 11 guards and 10 prisoners. The guards’ behaviour in particular sorted them into three distinct types – good guards, tough but fair, and mean guards. So this means that in order to perform a statistical analysis we would have to compare three subgroups consisting of 3 – 4 individuals to determine if there were significant differences in their personality traits. Statistically this is laughable. A basic principle of statistics is that significant differences between groups can only be detected if the sample sizes are adequately large, and the sample sizes in the SPE are so small as to be completely inadequate for the purpose. Now, let’s say that I was a researcher who wanted to test the hypothesis that individual differences in personality traits could predict behaviour in an experimental situation such as an in a mock prison. (Let’s also assume that I knew in advance what personality traits were relevant to the outcomes concerned.) I could actually estimate in advance what sort of sample size I would need in order to have a reasonable chance of finding a significant effect, if one existed. Using a procedure known as power analysis, I can calculate that if personality traits had a medium-sized effect on behaviour (i.e. about average compared to most effects in psychology) resulting in three different behavioural subgroups I would need about 50 or so participants per subgroup (so 150 in total) to have an 80% chance of finding a statistically significant effect if one actually existed. Even if the effects of personality were actually much larger than average, I would still need about 22 participants per subgroup, so 66 in total. Remember, that these numbers refer only to the number of guards. Presumably we would need an equivalent number of prisoners as well. This means that I could anticipate in advance that I would need a sample of between 132 to 300 participants to have a reasonable chance of getting a significant result. Therefore, I would look rather silly if I decided to settle for a grand sample of 21 people because I know that this number is simply not large enough to allow me to test my hypothesis in anything like a conclusive way. Therefore, I am led to believe that the SPE was not actually designed to test the hypothesis that personality traits would predict individual differences in behaviour.

In spite of these limitations, the original report on the SPE does note a number of non-significant trends for personality traits to predict behaviour. Specifically, prisoners who stayed until the end of the study, compared to the five who left early, scored higher on extraversion , conformity , empathy, and authoritarianism (Haney, et al., 1973). A reasonable interpretation of this finding is that personality traits deserve further investigation with a larger sample to determine if the results can be replicated. Yet in spite of this, Haney and Zimbardo (2009) have argued that “any trait-based explanations” of why participants behaved the way they did can be dismissed without any further consideration. This hardly seems reasonable to me.

Conclusions - the Power of Choice

In summary, the purpose of the SPE was supposed to be to demonstrate that powerful situational forces could over-ride individual dispositions and choices, leading good people to do bad things simply because of the role they found themselves in. If this were true, then participants in the study should have acted in a uniform way depending on their role. However, this was not the case, participants acted like individuals, showing that they still had the capacity to make choices within the constraints of their situations. Furthermore, the study was not even designed to provide a fair assessment of the influence of personality traits in such a situation because the sample size was nowhere near large enough to justify any definite conclusions. Far from demonstrating that individual differences do not matter in how people behave in a strong situation, the study’s results illustrate that even in undeniably tough situations people still have the capacity to make choices and that these choices matter. In fact, I would even go so far as to argue that personal choices matter even in real prisons, far more than Zimbardo might be willing to give credit for.

© Scott McGreal. Please do not reproduce without permission. Brief excerpts may be quoted as long as a link to the original article is provided.

[1] This blog post mentions some interesting results of this study regarding self-selection.

[2] To be fair, Zimbardo has stated, for example on his blog , that he believes that behaviour is a function of both individual differences and situational factors. However, many of his published remarks indicate that he sees dispositional and situational factors as competing with each other to explain behaviour. Personality psychologists see this “ competition ” hypothesis as being based on a false dichotomy. See this blog post by David Funder for example for an explanation of why this dichotomy is not valid.

[3] The sample was originally 24. Two were asked to remain on standby and one withdrew before the study began.

Image credit: Wikipedia

Follow up articles critiquing situationism that discuss the SPE

Challenging the "Banality" of Evil and of Heroism, Part 1 and Part 2 . This pair of articles refutes Zimbardo's claim that heroic and evil acts are equally "banal" outcomes of situational factors and that qualities within a person are of no real importance.

Further interesting reading

Don’t blame Milgram by David Funder – debunks the popular claim that Milgram’s obedience studies show that the “power of the situation” overwhelms the “power of the person”.

Can Situations Be Strong Or Weak? By JesseMarczyk

The Lie of the Stanford Prison Experiment – repost of exposé by Carlo Prescott, consultant on the SPE.

Challenging the Stanford Prison Experiment by Michael Barker

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 (5), 603-614. doi: 10.1177/0146167206292689

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

Haney, C., & Zimbardo, P. G. (2009). Persistent Dispositionalism in Interactionist Clothing: Fundamental Attribution Error in Explaining Prison Abuse. Personality and Social Psychology Bulletin, 35 (6), 807-814. doi: 10.1177/0146167208322864

Krueger, J. I. (2008). Lucifer's last laugh. The American Journal of Psychology, 121 , 335-341.

McFarland, S., & Carnahan, T. (2009). A Situation's First Powers Are Attracting Volunteers and Selecting Participants: A Reply to Haney and Zimbardo (2009). Personality and Social Psychology Bulletin, 35 (6), 815-818. doi: 10.1177/0146167209334781

Zimbardo, P. G. (2007). The Lucifer Effect: Understanding How Good People Turn Evil (1st ed.). New York: Random House.

Scott McGreal is a psychology researcher with a particular interest in individual differences, especially in personality and intelligence.

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What makes good people do bad things?

Former APA president drew from research to help explain evil under the backdrop of recent Iraqi prisoner abuses at Abu Ghraib.

By MELISSA DITTMANN

Monitor Staff

October 2004, Vol 35, No. 9

Print version: page 68

As the story goes, Dr. Jekyll uses a chemical to turn into his evil alter ego Dr. Hyde. In real life, however, no chemical may be needed: Instead, just the right dose of certain social situations can transform ordinarily good people into evildoers, as was the case with Iraqi prisoner abusers at Abu Ghraib, argued former APA president Philip G. Zimbardo, PhD, in a presidential-track program during APA's 2004 Annual Convention in Honolulu.

Indeed, Zimbardo--an emeritus psychology professor at Stanford University--highlighted how this Dr. Hyde transformation occurred among U.S. soldiers at Abu Ghraib by presenting classic psychology research on situational effects on human behavior.

Zimbardo, who will be an expert witness for several of the U.S. soldiers on trial, argued that situations pull people to act in ways they never thought imaginable.

"That line between good and evil is permeable," Zimbardo said. "Any of us can move across it....I argue that we all have the capacity for love and evil--to be Mother Theresa, to be Hitler or Saddam Hussein. It's the situation that brings that out."

Seduced into evil

In fact, the classic electric shock experiment by social psychologist Stanley Milgram, PhD, showed that when given an order by someone in authority, people would deliver what they believed to be extreme levels of electrical shock to other study participants who answered questions incorrectly.

Zimbardo said the experiment provides several lessons about how situations can foster evil:

Provide people with an ideology to justify beliefs for actions.

Make people take a small first step toward a harmful act with a minor, trivial action and then gradually increase those small actions.

Make those in charge seem like a "just authority."

Transform a once compassionate leader into a dictatorial figure.

Provide people with vague and ever-changing rules.

Relabel the situation's actors and their actions to legitimize the ideology.

Provide people with social models of compliance.

Allow dissent, but only if people continue to comply with orders.

Make exiting the situation difficult.

Particularly notable, Zimbardo said, is that people are seduced into evil by dehumanizing and labeling others.

"They semantically change their perception of victims, of the evil act, and change the relationship of the aggressor to their aggression--so 'killing' or 'hurting' becomes the same as 'helping,'" he said.

For example, in a 1975 experiment by psychologist Albert Bandura, PhD, college students were told they'd work with students from another school on a group task. In one condition, they overheard an assistant calling the other students "animals" and in another condition, "nice." Bandura found students were more apt to deliver what they believed were increased levels of electrical shock to the other students if they had heard them called "animals."

People's aggression can also increase when they feel anonymous--for example if they wear a uniform, hood or mask, Zimbardo said.

"You minimize social responsibility," he explained. "Nobody knows who you are, so therefore you are not individually liable. There's also a group effect when all of you are masked. It provides a fear in other people because they can't see you, and you lose your humanity."

For example, an experiment in 1974 by Harvard anthropologist John Watson evaluated 23 cultures to determine whether warriors who changed their appearance--such as with war paint or masks--treated their victims differently. As it turned out, 80 percent of warriors in these cultures were found to be more destructive--for example, killing, torturing or mutilating their victims--than unpainted or unmasked warriors.

What's more, a person's anonymity can be induced by acting in an anonymity-conferring environment that adds to the pleasure of destruction, vandalism and the power of being in control, Zimbardo noted.

"It's not just seeing people hurt, it's doing things that you have a sense that you are controlling behavior of other people in ways that you typically don't," Zimbardo said.

Zimbardo noticed that in his own simulated jail experiment in 1971--the Stanford Prison Experiment--in which college students played the roles of prisoners or guards, and the guards became brutal and abusive toward prisoners after just six days, leading Zimbardo to prematurely end the experiment. The experiment showed that institutional forces and peer pressure led normal student volunteer guards to disregard the potential harm of their actions on the other student prisoners.

"You don't need a motive," Zimbardo said. "All you really need is a situation that facilitates moving across that line of good and evil."

Prison abuses

The same social psychological processes--deindividualization, anonymity of place, dehumanization, role-playing and social modeling, moral disengagement and group conformity--that acted in the Stanford Prison Experiment were at play at Abu Ghraib, Zimbardo argued.

So is it a few bad apples that spoil a barrel? "That's what we want to believe--that we could never be a bad apple," Zimbardo said. "We're the good ones in the barrel." But people can be influenced, regardless of their intention to resist, he said.

As such, the Abu Ghraib soldiers' mental state--such as stress, fear, boredom and heat exhaustion, coupled with no supervision, no training and no accountability--may have further contributed to their "evil" actions, he noted.

"I argue situational forces dominate most of us at various times in our lives," Zimbardo said, "even though we'd all like to believe we're each that singular hero who can resist those powerful external pressures, like Joe Darby, the whistle-blowing hero of the Abu Ghraib prison."

Further Reading

Read more about Zimbardo's Stanford Prison Experiment at www.prisonexp.org .

Bandura, A., Underwood, B., & Fromson, M.E. (1975). Disinhibition of aggression through diffusion of responsibility and dehumanization of victims. Journal of Personality and Social Psychology, 9, 253-269.

Milgram, S. (1974). Obedience to authority: An experimental view. New York: Harper & Row.

Watson, J. (1973). Investigation into deindividuation using a cross-cultural survey technique. Journal of Personality and Social Psychology, 25, 342-345.

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Stanford Prison Experiment Shows How The Abuses At Abu Ghraib Could Be Perpetrated By Otherwise Good People

Dr. Philip Zimbardo, Professor Emeritus of Psychology at Stanford University, and who once conducted the now famous Stanford Prison Experiment, recently related the results of that 1971 experiment to the abuse discovered at Abu Ghraib. He said,

When the images of the abuse and torture in Abu Ghraib were revealed, immediately the military went on the defensive saying it’s a few bad apples. When we see people do bad things we assume they are bad people to begin with. But what we know in our study is: there are a set of social psychological variables that can make ordinary people do things they could never have imagined doing.”

The Stanford Prison Experiment was conducted over a six day period in a mock prison environment in the basement of one of the buildings at Stanford University. It demonstrated how ordinary people can perpetrate extraordinary abuses when placed in a cruel environment without clear rules, as shown in this short documenatry [13 min].

What Happens When You Put Good People In Evil Places?

We frankly didn’t anticipate what was going to happen. We tried to really test the power of the environment to change and transform otherwise normal people. Much as Milgram had changed or transformed otherwise normal people in an obedient situation, we wanted to do it in a prison-like situation.”

Experiment Participant Relates To The Guards At Abu Ghraib

What I first saw those photos, immediately a sense of familiarity struck me because I knew I had been there before. I’d been in this type of situation. I knew what was going on – in my mind.”

Source of images, video and quotes:   Youtube/The Stanford Prison Experiment

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