The famous Stanford Prison Experiment revisited
Revisiting the Stanford Prison Experiment: a Lesson in the Power of Situation
By PHILIP G. ZIMBARDO/The Chronicle of Higher Education
By the 1970s, psychologists had done a series of studies establishing the social power of groups. They showed, for example, that groups of strangers could persuade people to believe statements that were obviously false. Psychologists had also found that research participants were often willing to obey authority figures even when doing so violated their personal beliefs. The Yale studies by Stanley Milgram in 1963 demonstrated that a majority of ordinary citizens would continually shock an innocent man, even up to near-lethal levels, if commanded to do so by someone acting as an authority. The "authority" figure in this case was merely a high-school biology teacher who wore a lab coat and acted in an official manner. The majority of people shocked their victims over and over again despite increasingly desperate pleas to stop.
In my own work, I wanted to explore the fictional notion from William Golding's Lord of the Flies about the power of anonymity to unleash violent behavior. In one experiment from 1969, female students who were made to feel anonymous and given permission for aggression became significantly more hostile than students with their identities intact. Those and a host of other social- psychological studies were showing that human nature was more pliable than previously imagined and more responsive to situational pressures than we cared to acknowledge. In sum, these studies challenged the sacrosanct view that inner determinants of behavior — personality traits, morality, and religious upbringing — directed good people down righteous paths.
Missing from the body of social-science research at the time was the direct confrontation of good versus evil, of good people pitted against the forces inherent in bad situations. It was evident from everyday life that smart people made dumb decisions when they were engaged in mindless groupthink, as in the disastrous Bay of Pigs invasion by the smart guys in President John F. Kennedy's cabinet. It was also clear that smart people surrounding President Richard M. Nixon, like Henry A. Kissinger and Robert S. McNamara, escalated the Vietnam War when they knew, and later admitted, it was not winnable. They were caught up in the mental constraints of cognitive dissonance — the discomfort from holding two conflicting thoughts — and were unable to cut bait even though it was the only rational strategy to save lives and face. Those examples, however, with their different personalities, political agendas, and motives, complicated any simple conceptual attempt to understand what went wrong in these situations.
I decided that what was needed was to create a situation in a controlled experimental setting in which we could array on one side a host of variables, such as role-playing, coercive rules, power differentials, anonymity, group dynamics, and dehumanization. On the other side, we lined up a collection of the "best and brightest" of young college men in collective opposition to the might of a dominant system. Thus in 1971 was born the Stanford prison experiment, more akin to Greek drama than to university psychology study. I wanted to know who wins — good people or an evil situation — when they were brought into direct confrontation.
First we established that all 24 participants were physically and mentally healthy, with no history of crime or violence, so as to be sure that initially they were all "good apples." They were paid $15 a day to participate. Each of the student volunteers was randomly assigned to play the role of prisoner or guard in a setting designed to convey a sense of the psychology of imprisonment (in actuality, a mock prison set up in the basement of the Stanford psychology department). Dramatic realism infused the study. Palo Alto police agreed to "arrest" the prisoners and book them, and once at the prison, they were given identity numbers, stripped naked, and deloused. The prisoners wore large smocks with no underclothes and lived in the prison 24/7 for a planned two weeks; three sets of guards each patrolled eight-hour shifts. Throughout the experiment, I served as the prison "superintendent," assisted by two graduate students.
Initially nothing much happened as the students awkwardly tried out their assigned roles in their new uniforms. However, all that changed suddenly on the morning of the second day following a rebellion, when the prisoners barricaded themselves inside the cells by putting their beds against the door. Suddenly the guards perceived the prisoners as "dangerous"; they had to be dealt with harshly to demonstrate who was boss and who was powerless. At first, guard abuses were retaliation for taunts and disobedience. Over time, the guards became ever more abusive, and some even delighted in sadistically tormenting their prisoners. Though physical punishment was restricted, the guards on each shift were free to make up their own rules, and they invented a variety of psychological tactics to demonstrate their dominance over their powerless charges.
Nakedness was a common punishment, as was placing prisoners' heads in nylon stocking caps (to simulate shaved heads); chaining their legs; repeatedly waking them throughout the night for hourlong counts; and forcing them into humiliating "fun and games" activities. Let's go beyond those generalizations to review some of the actual behaviors that were enacted in the prison simulation. They are a lesson in "creative evil," in how certain social settings can transform intelligent young men into perpetrators of psychological abuse.
Prison Log, Night 5
The prisoners, who have not broken down emotionally under the incessant stress the guards have been subjecting them to since their aborted rebellion on Day 2, wearily line up against the wall to recite their ID numbers and to demonstrate that they remember all 17 prisoner rules of engagement. It is the 1 a.m. count, the last one of the night before the morning shift comes on at 2 a.m. No matter how well the prisoners do, one of them gets singled out for punishment. They are yelled at, cursed out, and made to say abusive things to each other. "Tell him he's a prick," yells one guard. And each prisoner says that to the next guy in line. Then the sexual harassment that had started to bubble up the night before resumes as the testosterone flows freely in every direction.
"See that hole in the ground? Now do 25 push-ups [expletive] that hole! You hear me!" One after another, the prisoners obey like automatons as the guard shoves them down. After a brief consultation, our toughest guard (nicknamed "John Wayne" by the prisoners) and his sidekick devise a new sexual game. "OK, now pay attention. You three are going to be female camels. Get over here and bend over, touching your hands to the floor." When they do, their naked butts are exposed because they have no underwear beneath their smocks. John Wayne continues with obvious glee, "Now you two, you're male camels. Stand behind the female camels and hump them."
The guards all giggle at this double-entendre. Although their bodies never touch, the helpless prisoners begin to simulate sodomy by making thrusting motions. They are then dismissed back to their cells to get an hour of sleep before the next shift comes on, and the abuse continues.
By Day 5, five of the student prisoners have to be released early because of extreme stress. (Recall that each of them was physically healthy and psychologically stable less than a week before.) Most of those who remain adopt a zombielike attitude and posture, totally obedient to escalating guard demands.
Terminating the Torment
I was forced to terminate the projected two-week-long study after only six days because it was running out of control. Dozens of people had come down to our "little shop of horrors," seen some of the abuse or its effects, and said nothing. A prison chaplain, parents, and friends had visited the prisoners, and psychologists and others on the parole board saw a realistic prison simulation, an experiment in action, but did not challenge me to stop it. The one exception erupted just before the time of the prison-log notation on Night 5.
About halfway through the study, I had invited some psychologists who knew little about the experiment to interview the staff and participants, to get an outsiders' evaluation of how it was going. A former doctoral student of mine, Christina Maslach, a new assistant professor at the University of California at Berkeley, came down late Thursday night to have dinner with me. We had started dating recently and were becoming romantically involved. When she saw the prisoners lined up with bags over their heads, their legs chained, and guards shouting abuses at them while herding them to the toilet, she got upset and refused my suggestion to observe what was happening in this "crucible of human nature." Instead she ran out of the basement, and I followed, berating her for being overly sensitive and not realizing the important lessons taking place here.
"It is terrible what YOU are doing to those boys!" she yelled at me. Christina made evident in that one statement that human beings were suffering, not prisoners, not experimental subjects, not paid volunteers. And further, I was the one who was personally responsible for the horrors she had witnessed (and which she assumed were even worse when no outsider was looking). She also made clear that if this person I had become — the heartless superintendent of the Stanford prison — was the real me, not the caring, generous person she had come to like, she wanted nothing more to do with me.
That powerful jolt of reality snapped me back to my senses. I agreed that we had gone too far, that whatever was to be learned about situational power was already indelibly etched on our videos, data logs, and minds; there was no need to continue. I too had been transformed by my role in that situation to become a person that under any other circumstances I detest — an uncaring, authoritarian boss man. In retrospect, I believe that the main reason I did not end the study sooner resulted from the conflict created in me by my dual roles as principal investigator, and thus guardian of the research ethics of the experiment, and as the prison superintendent, eager to maintain the stability of my prison at all costs. I now realize that there should have been someone with authority above mine, someone in charge of oversight of the experiment, who surely would have blown the whistle earlier.
By the time Christina intervened, it was the middle of the night, so I had to make plans to terminate the next morning. The released prisoners and guards had to be called back and many logistics handled before I could say, "The Stanford prison experiment is officially closed." When I went back down to the basement, I witnessed the final scene of depravity, the "camel humping" episode. I was so glad that it would be the last such abuse I would see or be responsible for.
Good Apples in Bad Barrels and Bad Barrel Makers
The situational forces in that "bad barrel" had overwhelmed the goodness of most of those infected by their viral power. It is hard to imagine how a seeming game of "cops and robbers" played by college kids, with a few academics (our research team) watching, could have descended into what became a hellhole for many in that basement. How could a mock prison, an experimental simulation, become "a prison run by psychologists, not by the state," in the words of one suffering prisoner? How is it possible for "good personalities" to be so dominated by a "bad situation"? You had to be there to believe that human character could be so swiftly transformed in a matter of daysnot only the traits of the students, but of me, a well-seasoned adult. Most of the visitors to our prison also fell under the spell. For example, individual sets of parents observing their son's haggard appearance after a few days of hard labor and long nights of disrupted sleep said they "did not want to make trouble" by taking their kid home or challenging the system. Instead they obeyed our authority and let some of their sons experience full-blown emotional meltdowns later on. We had created a dominating behavioral context whose power insidiously frayed the seemingly impervious values of compassion, fair play, and belief in a just world.
The situation won; humanity lost. Out the window went the moral upbringings of these young men, as well as their middle-class civility. Power ruled, and unrestrained power became an aphrodisiac. Power without surveillance by higher authorities was a poisoned chalice that transformed character in unpredictable directions. I believe that most of us tend to be fascinated with evil not because of its consequences but because evil is a demonstration of power and domination over others.
Such research is now in an ethical time capsule, since institutional review boards will not allow social scientists to repeat it (although experiments like it have been replicated on several TV shows and in artistic renditions). Nevertheless, the Stanford prison experiment is now more popular then ever in its 36-year history. A Google search of "experiment" reveals it to be fourth among some 132 million hits, and sixth among some 127 million hits on "prison." Some of this recent interest comes from the apparent similarities of the experiment's abuses with the images of depravity in Iraq's Abu Ghraib prison — of nakedness, bagged heads, and sexual humiliation.
Among the dozen investigations of the Abu Ghraib abuses, the one chaired by James R. Schlesinger, the former secretary of defense, boldly proclaims that the landmark Stanford study "provides a cautionary tale for all military detention operations." In contrasting the relatively benign environment of the Stanford prison experiment, the report makes evident that "in military detention operations, soldiers work under stressful combat conditions that are far from benign." The implication is that those combat conditions might be expected to generate even more extreme abuses of power than were observed in our mock prison experiment.
However, the Schlesinger report notes that military leaders did not heed that earlier warning in any way. They should have — a psychological perspective is essential to understanding the transformation of human character in response to special situational forces. "The potential for abusive treatment of detainees during the Global War on Terrorism was entirely predictable based on a fundamental understanding of the principles of social psychology coupled with an awareness of numerous known environmental risk factors," the report says. "Findings from the field of social psychology suggest that the conditions of war and the dynamics of detainee operations carry inherent risks for human mistreatment, and therefore must be approached with great caution and careful planning and training." (Unfortunately this vital conclusion is buried in an appendix.)
The Stanford prison experiment is but one of a host of studies in psychology that reveal the extent to which our behavior can be transformed from its usual set point to deviate in unimaginable ways, even to readily accepting a dehumanized conception of others, as "animals," and to accepting spurious rationales for why pain will be good for them.
The implications of this research for law are considerable, as legal scholars are beginning to recognize. The criminal-justice system, for instance, focuses primarily on individual defendants and their "state of mind" and largely ignores situational forces. The Model Penal Code states: "A person is not guilty of an offense unless his liability is based on conduct that includes a voluntary act or the omission to perform an act of which he is physically capable." As my own experiment revealed, and as a great deal of social-psychological research before and since has confirmed, we humans exaggerate the extent to which our actions are voluntary and rationally chosen — or, put differently, we all understate the power of the situation. My claim is not that individuals are incapable of criminal culpability; rather, it is that, like the horrible behavior brought out by my experiment in good, normal young men, the situation and the system creating it also must share in the responsibility for illegal and immoral behavior.
If the goals of the criminal system are simply to blame and punish individual perpetrators — to get our pound of flesh — then focusing almost exclusively on the individual defendant makes sense. If, however, the goal is actually to reduce the behavior that we now call "criminal" (and its resultant suffering), and to assign punishments that correspond with culpability, then the criminal-justice system is obligated, much as I was in the Stanford prison experiment, to confront the situation and our role in creating and perpetuating it. It is clear to most reasonable observers that the social experiment of imprisoning society's criminals for long terms is a failure on virtually all levels. By recognizing the situational determinants of behavior, we can move to a more productive public-health model of prevention and intervention, and away from the individualistic medical and religious "sin" model that has never worked since its inception during the Inquisition.
The critical message then is to be sensitive about our vulnerability to subtle but powerful situational forces and, by such awareness, be more able to overcome those forces. Group pressures, authority symbols, dehumanization of others, imposed anonymity, dominant ideologies that enable spurious ends to justify immoral means, lack of surveillance, and other situational forces can work to transform even some of the best of us into Mr. Hyde monsters, without the benefit of Dr. Jekyll's chemical elixir. We must be more aware of how situational variables can influence our behavior. Further, we must also be aware that veiled behind the power of the situation is the greater power of the system, which creates and maintains complicity at the highest military and governmental levelswith evil-inducing situations, like those at Abu Ghraib and Guantánamo Bay prisons.
(Philip G. Zimbardo is a professor emeritus of psychology at Stanford University and author of The Lucifer Effect: Understanding How Good People Turn Evil, published this month by Random House.)