Statement from PHILIP ZIMBARDO

Blogger Ben Blum (Medium, June 7, 2018) recently questioned the authenticity and value of the 1971 Stanford Prison Experiment (SPE), labeling it a “fraud” and a “lie,” and other commentators have followed suit. For example, after watching a video that I deposited with the Stanford Archives, Brian Resnick wrote, “This damning video debunks the famed experiment” (VOX, June 14, 2018), and Jay Van Bavel told LIVE-SCIENCE (June 12, 2018), “The bottom line is that conformity isn't natural, blind or inevitable.” French author Thibault LeTextier (2018) even published a book-length critique entitled History of a Lie.

In this response to my critics, I hereby assert that none of these criticisms present any substantial evidence that alters the SPE’s main conclusion concerning the importance of understanding how systemic and situational forces can operate to influence individual behavior in negative or positive directions, often without our personal awareness. The SPE’s core message is not that a psychological simulation of prison life is the same as the real thing, or that prisoners and guards always or even usually behave the way that they did in the SPE. Rather, the SPE serves as a cautionary tale of what might happen to any of us if we underestimate the extent to which the power of social roles and external pressures can influence our actions.


What was the Stanford Prison Experiment, and what serendipitous events catapulted this academic experiment about situational power into national prominence? The SPE was a study conducted at Stanford University over six days, August 14-19, 1971, designed and conducted by me, as principal investigator, along with my research team of graduate students, Craig Haney and William Curtis Banks, undergraduate David Jaffe, and prison consultant, Carlo Prescott. It was an exploratory investigation of the extent to which the power of situational forces could transform individual behaviors of participants. Twenty-four college students, recruited from a newspaper ad to participate in a study of prison life, first completed a battery of psychological tests and surveys (in order to establish that they were healthy and normal, and had not had any prior experience of breaking the law). These students were then randomly assigned the roles of prisoner and guard. The guards worked 8-hour shifts, while the prisoners lived full time in a mock prison setting created in the basement of the Stanford psychology department. Stanford’s Human Subjects Research Office approved this unique experiment, within the guidelines they provided. The intended two-week experiment was terminated  after 6 days because of the unexpectedly extremely negative reactions of many  of the mock guards and prisoners. Full details of this study are available in my book The Lucifer Effect (2007) and online at


Shortly after the SPE ended, dramatic events in two American prisons—San Quentin and Attica—brought prison conditions into the national limelight. On August 21, during an alleged escape attempt by Black political prison activist George Jackson, a number of San Quentin guards and prisoners were killed. From September 9-13, a thousand Attica prisoners took control of that facility in public protest against Jackson’s “murder.” That confrontation ended with National Guardsmen killing many of those prisoners as well as their prison guard hostages. Extensive news coverage and congressional investigations ensued, and I was invited to participate in both media interviews and congressional hearings, which generated considerable interest in what had happened in our mock prison.

Before responding to questions about whether I portrayed the SPE honestly and accurately, it's important to note that I have gone to great lengths to make every bit of documentary information from the SPE publicly available in the archives of Stanford University and Akron University’s Museum of Psychology. This information includes more than 40 boxes of observational data; prisoner, guard, and staff reports; diaries that were gathered during and following the study; and 12 hours of videos made during the study. The Lucifer Effect also contains 10 chapters devoted to various aspects of the SPE, with full documentation as to the source of every assertion. In addition, a considerable amount of material about the SPE has been available on the Stanford Prison Experiment website for more than 15 years. Thus, contrary to critics who imply that they've unearthed new information that I kept hidden, the SPE has been a model of open science long before practices such as public archiving and data sharing were common.

Critics also claim that my place in modern psychology is based primarily on the SPE. However, my reputation derives from considerable research and theories on many topics, both before and after the SPE. Indeed, I was already a tenured full professor at Stanford and nearly 40 years old by the time that the SPE was conducted in 1971, and it was my earlier work at New York University that led me to be invited to author one of the leading introductory psychology texts, Psychology and Life (over 12 editions), and later Psychology: Core Concepts. Subsequently, I was chosen from a group of textbook authors to become the creator and narrator of the 26-part TV series, Discovering Psychology, which has been viewed by millions of students and teachers around the world. I suspect that my place within psychology derives as much from those contributions, if not more so, than it does from the SPE itself. Overall, I have contributed to 40 different areas of psychology, as documented in more than 60 books and 600 publications that I have written so far.

In this reply, I will first address claims about the alleged fraudulent nature of the experiment’s process and conclusions. I will detail some of the study’s unique features, discuss its scientific validity, and describe several real-world applications. Finally, I will conclude by outlining some unexpectedly valuable extensions derived from my SPE experiences and reflections.


Recent criticisms of the SPE have focused on six issues, each of which I will address in turn.

1.  A staff member publicly denounced the SPE as flawed and dishonest. Blum cites a 2005 op-ed in the Stanford Daily student newspaper allegedly written by SPE prison consultant Carlo Prescott and entitled “The lie of the Stanford Prison Experiment.” In fact, Blum even borrowed the op-ed title as the core theme for his blog. The reality is that Carlo never wrote a word of that op-ed. He and I had become friends after our first meeting in my social psychology class in May 1971, and after I learned that he had served time in prison, I invited him to serve as SPE's expert advisor on prison life. A careful reading of the student newspaper op-ed makes evident that the writer had a very distinctive legalistic style and vocabulary, not at all like Carlo’s. It turns out that its real author, who also published many related negative SPE comments online, was Michael Lazarou, a Los Angeles movie writer. He had befriended both Carlo and me in an attempt to get me to agree to give him screen rights to a Hollywood movie about the SPE. When I chose instead to go with Maverick Films producer Brent Emery, Lazarou began writing critiques of the SPE (Brent Emery’s phone records indicated, “Carlo said it was NOT him, but all from Lazarou,” May 7, 2005). In other words, it is simply not the case that the SPE prison consultant referred to the study as a lie.


2.  The staff's instructions for guards to be "tough" biased the guards' behavior and distorted the research outcomes. The SPE was designed as a mock prison simulating some of the main features that characterized the American prison system at that time. Central in the training of guards was to exercise their power over the prisoners so that they maintained order, prevented rebellion, and eliminated escape attempts. My instructions to the guards, as documented by recordings of the guard orientation, were that they could not hit the prisoners but could create feelings of boredom, frustration, fear, and "a sense of powerlessness—that is, we have total power of the situation, and they have none." We did not give any formal or detailed instructions about how to be an effective guard.

None of the participants wanted to be a guard, but half were randomly assigned to that role. As shown in a documentary film on the SPE, entitled Quiet Rage, the guards took awhile to get into their role; videos from the first day show them giggling while encouraging prisoners to take the rules seriously. One of three guards on a shift that day left the area during a prisoner count and wasn't even requiring prisoners to follow orders issued by the other guards, so David Jaffee, acting as the SPE Warden, took this guard aside and asked him to become more active, involved, and "tough" in order to make the experimental setting seem more like a prison. Here are his exact words:


We noticed this morning that you weren't really, you know, lending a hand, and I was wondering if there's anything's wrong… We really want to get you active and involved because the guards have to know that every guard is going to be what we call a “tough guard”… what I mean by tough is [that] you have to be firm, and you have to be in the action… It’s really important… for the workings of the experiment [because] whether or not we can make this thing seem like a prison—which is the aim of the thing—depends largely on the guards’ behavior.


Asking a person role-playing a guard in a prison simulation to be "firm" and "in the action" is mild compared to the pressure exerted by actual wardens and superior officers in real-life prison and military settings, where guards failing to participate fully can face disciplinary hearings, demotion, or dismissal. Although the research team asked all guards to be actively involved and firmly in control of the prisoners, it never instructed guards to employ brutality, and it explicitly banned the use of physical force.

Despite the request David Jaffee made, none of the guards behaved in a dominant way during the first two shifts. What made a difference was that on Day 2 the prisoners rebelled with verbal and physical confrontations challenging the full complement of nine guards. After the guards put down this rebellion, one of them declared that prisoners were "dangerous," and with that new view of the situation, several guards became much tougher in their actions.

It's important to note that in all my reports about the SPE, I have always highlighted individual differences among the guards. One or two guards on each shift became progressively meaner over time, others maintained a more even-tempered style, and a few were considered “good guards” from the prisoners’ perspectives. However, none of the “good guards” ever intervened to prevent the cruelty of their fellow guards. Even Blum acknowledges these individual differences among the guards. From my perspective, the range of guard behaviors undercuts any criticisms of the alleged demand characteristics that presumably distorted the results of the SPE. The fact that some guards remained "good guards" throughout the study shows that cruel guards chose to act on their own initiative. It is their extreme behaviors that generated the dramatic effects of the study, most notably those of the iconic guard nicknamed “John Wayne” for his macho performance.


3.  One guard was intentionally play-acting his role. The prisoners nicknamed one guard on the night shift “John Wayne” because he acted like an out-of-control, Wild West cowboy. However, some critics have dismissed this guard's behavior as merely play-acting the role of tough guard. After the experiment, “John Wayne” (David Eshelman) explained that he modeled his role after the warden in the movie Cool Hand Luke. He said he wanted to be a realistic guard, so he stepped up to lead his night shift to be really tough on the prisoners. He did so by punishing prisoners repeatedly with extensive push-ups (occasionally, with some prisoners stepping on the back of others), limiting food access, or issuing arbitrary rules. With each passing night, he became more creatively evil in ways that went beyond being a tough guard. Indeed, he later said that he began to think of himself as a “puppeteer” who made prisoners do whatever he chose. In an extreme perversion of his experimentally assigned role, he devised an unthinkable way to humiliate all prisoners on the fifth night of the study. He ordered them to think of themselves as “camels,” half as males and the other half as females. Those ordered to be female camels had to bend over, while the male camel prisoners were ordered to hump them “doggy style,” which they reluctantly did by simulating sodomy. A video recording, made in my absence, indicated this episode lasted nearly ten minutes with all three guards shouting epithets and laughing hysterically. Fortunately, I had earlier decided to terminate the experiment the next morning.

 Prison Guard "John Wayne"

I think it goes without saying that such actions go far beyond simply playing the role of a tough guard. It is also worth noting that Eshelman's fellow guards fully participated in these activities and other offensive behaviors that typified their shift—activities that were strikingly similar to the sexually degrading rituals imposed on Iraqi prisoners by American prison guards in Abu Ghraib Prison. Moreover, the night shift was not alone in excessively brutalizing the SPE prisoners; several guards on the other two shifts also regularly engaged in acts designed to humiliate the prisoners. Were these acts of brutality—and their striking parallels with real-world prison atrocities—nothing more than a function of social demand characteristics in a fraudulent "sham" study, as Blum and other critics have argued, or do they tell us something important about human nature? The full body of available evidence clearly suggests the latter.


4. A prisoner who seemed to have an emotional breakdown was actually just faking the breakdown to leave the study early. Blum portrays the case of Doug Korpi, alias Prisoner 8612, as an instance of me being duped into believing that a prisoner was having an emotional breakdown when in fact the prisoner was simply faking a breakdown in order to leave the study early. The evidence Blum cites for this conclusion is that Korpi told Blum in an interview: "I was faking… If you listen to the tape, you can hear it in my voice... I was being a good employee. It was a great time.” To this criticism, I have two responses. First, I would argue that any researcher who believes a research participant is having a breakdown is ethically obliged to treat the breakdown as real, even if the breakdown later turns out to be feigned. And second, I'm not alone in regarding the breakdown as real, because Doug Korpi himself went on record in Quiet Rage as saying that his time as a prisoner was the most upsetting experience of his life—an experience so profound that he went on to become a prison psychologist (see the accompanying video).

For reasons I cannot fathom, Korpi’s story has changed several times over the past 47 years: from genuinely losing control of his emotions, to getting out of the study so that he could lead an insurrection and liberate the other prisoners, to faking a breakdown just to get out early and study for an upcoming Graduate Record Exam, to other reflections and memory distortions. Regardless, the conclusions Korpi drew from the study in his Quiet Rage interview—17 years after the experience—are fully consistent with my own conclusions: "The Stanford Prison was a very benign prison situation, and it still caused guards to become sadistic [and] prisoners to become hysterical."

5.   A British research team failed to replicate the SPE. An “experiment” based loosely on the SPE was filmed and broadcast on a 4-part BBC-TV show in May 2002 (Koppel & Mirsky, 2002). Its results appeared to challenge those of the SPE because the guards showed little violence or cruelty toward the prisoners. Instead, the opposite occurred. The prisoners dominated the guards, to the point where the guards became “increasingly paranoid, depressed and stressed and complained most of being bullied.” Several of the guards couldn’t take it anymore and quit; none of the prisoners did so. Blum points to that TV show as another challenge to the validity of the SPE. However, in no way did this “reality-show” meet the scientific criteria for a replication.

From the time of being recruited with national ads to be actors in a "university-backed social science experiment to be shown on TV," every participant knew their actions and voices (from lapel mics they had to wear always) would be seen and heard on national TV by family and colleagues. Any similarity to the intense build-up of emotional confrontations between SPE guards versus prisoners, 24/7, was diluted by the daily itinerary of the British research team (Alex Haslam and Stephen Reicher). These researchers frequently intervened, made regular public broadcasts into the prison facility, administered daily psychological assessments, arranged contests for the best prisoners to compete to become guards, and as in many “reality-TV” shows, created daily "confessionals" for participants to talk directly to the camera about their feelings. Ironically, the results of this show could be interpreted as further evidence of the “power of the situation,” although in this case the “situation” was that of reality-TV.

Among the participants in this BBC-TV prison show, several of whom had contacted me afterwards, was Philip Bimpson, the ringleader of a prisoner rebellion against the hapless guards. He said, in part:


The prisoners won because they had organized themselves quicker than the guards; their subversive actions and organizational skills outwitted the guards who were disorganized in their new surroundings. They did not understand that they had to organize themselves and form a set of rules that they all agreed on… I think the group is being exploited by the BBC for commercial gain. Me and my new friends in the group joined the experiment for the furtherance of science & not to be used as a form of cheap entertainment." (Personal email communication, 26 Feb. 2002; supplemented by my subsequent visit in Glasgow, Oct. 10, 2004)


I therefore reject the use of this “replication” as a scientifically valid challenge to results from the SPE (for a more detailed response to this criticism, please see my article in the British Journal of Social Psychology, 2007, Vol. 127.).


6.   Early publications appeared outside peer-reviewed journals to avoid rejection. Several critics have claimed that I chose to publish early accounts of the SPE outside peer-reviewed journals in order to avoid likely rejection. That is not the case. The research team published its first account of the SPE in Naval Research Reviews because I had used funds from ONR that were left over from a previous grant, and ONR insisted that I document my research in its journal. Our next publication was in the International Journal of Criminology and Penology, at the invitation of the editor. In 1973, I then published an account of the SPE in the New York Times Magazine—not to bypass peer review, but to reach a large national audience and use the opportunity to frame the SPE as a Pirandellian Prison. My colleagues and I subsequently published several other articles and chapters about the SPE in peer-reviewed journals and books for academic audiences, including the American Psychologist, which is rigorously peer-reviewed.

Now I want to turn to some other issues: highlighting what is unique about the SPE; describing its scientific and conceptual validations; showing how it has influenced decisions in legal settings; and discovering how the U.S. military has applied one of its main conclusions. I then turn to reflect on three of its enduring positive extensions in the domains of shyness, time perspective, and heroism.




Uniqueness of the SPE

The design of the SPE is unique in social psychological research by enabling observations of behavior patterns of the participants during an extended period of more than 120 hours. One of its main conclusions is that participants who were randomly assigned to roles of prisoner or guard gradually assumed those new identities in a simulated prison setting, despite their awareness of its experimental nature. Most other research is typically compressed into a one-hour session, so it is not possible to observe the emergence of situated identities, such as some normal, healthy college students becoming either cruel guards or helpless prisoners.



Scientific Validation

Replication with variations by independent researchers is the hallmark of all experimental research, and so it was with the SPE. A team of researchers at the University of New South Wales, Australia, extended the SPE design by having one condition similar to ours and several other experimental variants to explore how social organizations influence the relationship between prisoners and guards (Lovibond, Mithiran, & Adams, 1979). Their "Standard Custodial" regime was modeled on medium security prisons in Australia and was closest in its procedure to the SPE. The researchers' central conclusion of their rigorous experimental protocol notes: "Our results thus support the major conclusion of Zimbardo et al. that hostile, confrontive relations in prisons result primarily from the nature of the prison regime, rather than the personal characteristics of inmates and officers." (pp. 283). These results, within this research design, also help offset skepticism about the validity of such simulation experiments by providing baselines to assess behavioral changes from objectively defined structural characteristics of real-life prisons. However, it should be noted that it is no longer possible for anyone to attempt a full replication of the SPE, given the critiques that it is not ethical to ever conduct this type of research again.



The Enduring Value of SPE’s Message in Legal Settings

I have spent much of my professional career trying to bridge the translation of research findings into social change efforts that promote social justice and what is best in human nature. In their hearings on prison reform (October, 1971), the Subcommittee of the United States Congress House of Representatives wanted not only my analyses, but also recommendations for reform. In my statement in the Congressional Record, I clearly advocated for congressional intervention into the prison structure to bring about improvements in the condition of inmates, as well as for correctional personnel. In addition, I wish here to highlight the important contributions that Craig Haney has made to prison reform. He is widely regarded as the foremost expert in the nation on the psychology of imprisonment, notably in challenging conditions of solitary confinement and the death penalty. Craig’s expertise is based on having earned both a Ph.D. in psychology and a law degree from Stanford University.

Unfortunately, blogger Blum’s Medium critique misrepresents published testimony in the Congressional Record about my constructive arguments for improving our nation’s mass incarceration system. My advocacy has largely taken the form of consciousness-raising about the necessity for ending the “social experiment” of prisons because, as measured by high rates of recidivism and current mass levels of incarceration in the United States, that experiment has failed. We must find the reason for that through more thorough systems analyses, and propose alternative solutions to incarceration.

 Carol M. Highsmith's America, Library of Congress, Prints and Photographs Division.

My second testimony before a Congressional subcommittee that focused on juvenile detention (September, 1973) moved me further toward becoming a social advocate. I outlined 19 separate recommendations for improved treatment of detained juveniles. I was pleased to learn that a new federal law was passed that was in part stimulated by my testimony. Senator Birch Bayh, who headed this investigation, helped to put into law the rule that, to prevent juveniles being abused, juveniles in pre-trial detention should not be housed with adults in federal prisons.

One powerful legal impact of the SPE derived from my participation in the Federal Court trial of Spain et al. versus Procunier et al. (1973). The "San Quentin Six" prisoners had been isolated in solitary confinement for several years for their alleged involvement in the murder of guards and informer prisoners during the escape attempt of George Jackson on August 21, 1971. As an expert witness, I toured the facilities of San Quentin's maximum adjustment center and interviewed each of the six prisoners a number of times. My prepared statement and two days of trial testimony concluded with the opinion that all of these prison conditions of involuntary, prolonged, indefinite confinement under dehumanizing conditions constitutes "cruel and unusual punishment" and must therefore be changed. The Court arrived at a similar conclusion and ordered improved living conditions for inmates. In addition, I served throughout the trial as a psychological consultant to the team of lawyers for the plaintiffs.

Later, in 2004, I was asked to be an expert witness in the military trial of American prison guard, Staff Sgt. Chip Frederick. He was a leader of the guards on the night shift in Abu Ghraib Prison, all of whom participated in brutalizing Iraqi prisoners. There were many apparent similarities between the incidents of prisoner abuse by the guards in Abu Ghraib and the SPE. Frederick’s behaviors were shown to be completely atypical, as he had no prior history of such harmful actions towards any other people, and instead had been given many honors for his outstanding military service. Although he admitted his guilt in committing these abuses in Abu Ghraib, his prison sentence was shortened considerably by the judge’s acknowledgement of my testimony documenting the power of the situation in that unusual prison.

Interestingly, I was also asked to be an expert witness in the federal trial of Alex Blum, the cousin of Ben Blum, who mentions him in his Medium blog. Briefly, Alex was a guilty party as get-away driver in a bank robbery along with three other U.S. Rangers. Alex had long obsessed about becoming a U.S. Ranger, and as a recruit, he was assigned to an officer, Luke Elliot Sommer, who was his taskmaster and who issued orders to be obeyed without question. One of them was to assist in a “practice drill” of robbing a local bank, but in fact, it turned out to be a full-scale bank robbery. I spent enough personal time with Alex to realize the extent to which he was “blindly obeying" the authority of Capt. Sommer (who got a 24-year prison sentence). Alex might have received a similar long sentence, but instead it was reduced to only 16 months, presumably because the court accepted the expert testimony. When in prison, it took Alex a full eight months to come to the realization that what he had done was a real bank robbery and not a ranger drill, which for me demonstrated the power of his “Ranger-Mindset” of total obedience to his assigned authority. It was a powerful combination of Milgram’s obedience scenario along with cult-leader mind control, as seen in the Jonestown followers of Jim Jones, and those of Rev. Moon. For valuable information on mind control, see Steven Hassan’s Combating Cult Mind Control (2015).



Situationally-Based Behavioral Explanations Are Never Forms of “Excusiology”

“What social psychology has given to an understanding of human nature is the discovery that forces larger than ourselves determine our mental life and our actions—chief among these forces is the power of the social situation” (Banaji, 2001, Psychological Science Agenda).

In Solomon Asch’s classic research (1955), the power of a group majority distorted the perceptual judgments of individual college students. In Stanley Milgram’s obedience research (1963), the power of an authority figure induced actions that went against the moral conscience of adult male participants to harm a stranger. In experimental research on moral disengagement, Albert Bandura (1975) showed that college student participants shocked the “errors” of other students with highest intensity when they had been labeled “animals,” compared to other conditions. In the SPE, we witnessed the creation over time of two mentalities, that of dominating guards and of helpless, hopeless prisoners in a setting that validated these alternative personas. I believe that these four psychological studies, among others in our discipline, illustrate the extent to which the power of a social situation can come to dominate and distort individual perceptions, judgments, values and behaviors.


It should be made crystal-clear that when social psychologists attempt to explain the behavior of individuals in terms of influential external situational forces, they are never implying that personal responsibility is absolved. People are always responsible for the consequences of their actions—personally, socially and legally. Understanding why we do something does not excuse our liability for the outcomes of that behavior.

Nevertheless, some critics of the SPE display a naïve misunderstanding of this perspective by claiming that a message of the SPE is that individuals "cannot really be held accountable for the sometimes reprehensible things we do . . . it is also profoundly liberating. It means we're off the hook” (Blum, 2018). Similarly, LeTextier (2018) proclaims: “It’s like, ‘Oh my god, I could be a Nazi myself. I thought I was a good guy, and now I discover that I could be this monster.’ And in the meantime, it’s quite reassuring, because if I become a monster, it’s not because deep inside me I am the devil, it’s because of the situation. I think that’s why the (SPE) experiment was so famous in Germany and Eastern Europe. You don’t feel guilty. ‘Oh, okay, it was the situation. We are all good guys. No problem. It’s just the situation made us do it.’ So it’s shocking, but at the same time it’s reassuring.”

This argument was rejected in the Nuremberg trials of Nazi doctors and others many decades ago, and with good reason; the individuals were indeed “just doing their job” but were still held accountable for the atrocities they committed.

I strongly reject the criticism that the underlying message of the SPE is to absolve people of their “sins.” Changing or preventing undesirable behavior of individuals or groups requires an understanding of what strengths, virtues, and vulnerabilities that they bring into any given situation. We need to recognize more fully the complex of situational forces that are operative in given behavioral settings. Modifying them, or learning to avoid them, can have a greater impact on reducing undesirable individual reactions than remedial actions directed only at changing the people in a situation after they have done wrong. That means adopting a public health approach in place of the standard medical model approach to curing individual ills and wrongs. I have stated repeatedly that attempting to understand the situational and systemic contributions to any individual's behavior does not excuse the person or absolve him or her from responsibility in engaging in immoral, illegal, or evil deeds. Furthermore, I've always endorsed all efforts to create conditions, systemic and social, which can bring out the best in human nature.



Military Use of SPE in SERE Trainings

When I lectured at the United States Naval Academy, I was informed that the Navy and other military units train their personnel using the documentary footage of the SPE to avoid the excesses that are likely to occur during these exercises. Following the Korean War, when some airmen were alleged to have given actionable information to the enemy, our military developed a policy of never giving any information when captured by any enemy, other than name, rank and serial number. The military instituted war games in which some personnel acted as escaped prisoners who were hunted down by other staff, and then interrogated as intensely as possible in order to break them down into giving confessions and vital information. This program, Search, Evasion, Resistance, Escape (SERE) continues to function as one effective training program to achieve the desired objective of never complying with any enemy commands for information. However, there have been reports of excesses practiced by the simulating interrogators, which were dangerous to the well-being of the simulating captives. The SPE is shown as a warning of the ease in which anyone can cross the line from play-acting to becoming cruel torturers. I found this to be an unexpected positive outcome of some of SPE’s messages in real-world settings.



SPE as Pirandellian Prison

The opportunity to contribute an article to the New York Times Magazine (1973) allowed our research team to present our experience to a larger public audience, rather than limit it to academics only. This meant that we had to engage in a different style of writing. I valued the idea of framing the SPE in terms of playwright Luigi Pirandello's metaphors of the thin line between reality and illusion, between acting and being, between role-playing and the role becoming the self, and so that is what we did.

The SPE was a drama that was enacted by young men playing their assigned roles without scripted lines and without an audience for hours and days on end. Everyone knew it was only a play. Everyone knew it was just a psychology experiment; that they were in the basement of the psych department, not a real prison; that the prisoners had not committed any crimes; that the guards could have earned their salary by simply playing cards in their guard office for much of their 8-hour shift as long as they kept prisoners locked in their cells. But in a relatively short time frame, the psychology study became a “prison,” and the only two ways out of that dungeon were to be released by the arbitrary decision of the parole board or by becoming/acting seriously disturbed mentally or physically. In addition to Korpi, four other mock prisoners had to be released early for extreme emotional or medical reasons.

As is also apparent from our documentary videos and verbatim transcripts, not only did most of the research participants enact their roles as if they were imprisoned or were doing their job as paid guards, but almost everyone else who got engaged in that setting acted as if it were a real prison. The prime example is the Catholic priest who I had invited to evaluate the fit of this experiment with his experience in real prisons. He did so by interviewing all the prisoners. However, he soon got into the role of prisoner counselor, calling a prisoner’s mother to inform her that her son needed a public defender to help get him out of this prison. The public defender also knew the SPE was just an experiment, but when meeting with the desperate prisoners, he maintained his aloof role that was legally limited to what he could do to help them.

Carlo Prescott got so involved in his role as head of the parole board that he began to chastise and verbally abuse many of those pleading to be paroled, until some cried and begged for his understanding of their case. He later said that he had unconsciously become the kind of person he had hated most in the world, the parole board authorities that had turned down his own requests dozens of times before. Afterwards, he reported becoming sick to his stomach, realizing what he had become, and he did not want to play that role ever again.

And then there was me. I began the study as the principal research investigator, in charge of my team of student researchers, all interested in exploring together the dynamics of a unique situation we had created. I had initially instituted observational and research protocols, video recording assignments, and data collection procedures, as all experimental researchers do. However, over a very short time, I was transformed into the full-time role of Prison Superintendent. In my view, that is the major flaw of the SPE; it had no independent scientific observer of the unfolding events. My agenda became less about data collection than about daily staff assignments, timing of meals, meeting with concerned parents, parole board sessions, guard shift changes, meeting with the prisoner grievance committee, dealing with prisoner breakdowns, and more.

One vivid illustration of this flaw in the study came on Thursday night, five days into the study, when there was the usual 10:00 pm scheduled toilet run—the last time prisoners could go to a regular toilet rather than urinate or defecate in buckets in their cells. The night shift guards used this event as an opportunity to torment and confuse the prisoners in various ways. By then, I no longer acknowledged the suffering of the prisoners; the toilet run was only a checkmark on my daily schedule.

That's when I received an unexpected challenge from a visitor observing how the guards were dehumanizing and tormenting the prisoners (again without any staff direction). Christina Maslach, a new psychology professor at U.C. Berkeley, whom I was dating, came down to take me out to dinner. However, when she saw the ongoing treatment of the hooded, chained prisoners, she ran outside in tears. We had a major confrontation in which she made clear that this situation had changed me from a teacher who loved students into someone who could be indifferent to student suffering. She then said she didn't want to continue our relationship if I did not come to my senses. That was my wake-up call to shed the Prison Superintendent garb, return to my usual persona, and terminate the SPE the next morning.

So what really happened in the five days of the SPE? Was it an unfolding drama of human nature in its worst apparel, or just kids play-acting to please the director? I strongly believe the former.



Enduring Legacies

Three of my contributions to psychology and society have emerged in various ways from extensions of ideas I extracted from the SPE. They are: (1) understanding and treating shyness, (2) understanding and utilizing the power of time perspective to improve the quality of our lives, and (3) creating the Heroic Imagination Project to inspire compassionate social action for good and against evil.

Shyness. I first conceptualized shyness in 1972 as a self-imposed psychological prison in which the shy individual plays the dual roles of guard (who limits all freedom of speech and social behavior) and also the reluctant prisoner (who submits to those constraints and thus loses much self-esteem). I went on to do pioneering research on this topic, created the first shyness treatment clinic (still in operation at Palo Alto University), and also published several popular books and magazine articles for the general public. Thus, I have integrated education, research, therapy, and public awareness of this widespread personal and social phenomenon.

Time Perspective. My interest in exploring the psychology of time perspective, or the temporal zones in which we all live, emerged in part from the sense of distorted time we all experienced during the SPE. Without clocks or windows, that basement prison’s time revolved around each guard shift coming and going. We often felt trapped in an expanded present time zone when the guards were endlessly harassing the prisoners, or in a present fatalistic time zone that most prisoners experienced when nothing they did made a difference in how they were treated. I subsequently developed a scale to measure individual differences in time perspective, the Zimbardo Time Perspective Inventory; conducted original research on the topic; published several books on time perspective and its applications in various kinds of therapy both to heal trauma and to improve the quality of our lives. In addition, I have brought together a global team of researchers and practitioners studying, using, and extending the ideas and procedures that emerged in part from one of my many personal experiences during the SPE.

Creating Everyday Heroes. In the final chapter of The Lucifer Effect, I switched focus from trying to understand how good people can turn evil to asking whether it is possible for ordinary people to be inspired and trained to become everyday heroes. Since then, and with support of colleagues following my public statement of that theme in my 2008 TED talk, On the Psychology of Evil, I've devoted my academic and personal life to creating a nonprofit foundation, The Heroic Imagination Project (HIP). Its mission is to inspire and train ordinary people, especially our youth, to be ready and willing to enact extraordinary deeds of compassion in challenging situations they face in their lives. In addition to a research agenda, we have developed a unique educational program that provides the foundation for training people how to think and act heroically in situations they face. These lessons have demonstrated effectiveness with high school and college students, as well as in business settings. HIP has become a global movement with vibrant programs in more than a dozen nations on several continents, with many more coming on board soon. For more information, please visit

I hope that this reply to the critics of the legitimacy and enduring value of the SPE help make evident that they are substantially wrong in their conclusions. For whatever its flaws, I continue to believe that the Stanford Prison Experiment contributes to psychology’s understanding of human behavior and its complex dynamics. Multiple forces shape human behavior: they are internal and external, historical and contemporary, cultural and personal. The more we understand all of these dynamics and the complex way they interact with each other, the better we will be at promoting what is best in human nature. That has been my lifelong mission.