Monday, January 14, 2008


A Simulation Study of the Psychology of Imprisonment Conducted at Stanford University
What happens when you put good people in an evil place? Does humanity win over evil, or does evil triumph? These are some of the questions posed in this dramatic simulation of prison life conducted in the summer of 1971 at Stanford University.

Zimbardo, P.G. (2007)

How we went about testing these questions and what we found may astound you. The planned two-week investigation into the psychology of prison life had to be ended prematurely, after only six days because of what the situation was doing to the college students who participated.

It began on a quiet Sunday morning in August, in Palo Alto, California, where the individual suspects were suddenly arrested, put in the rear of a police car and carried off to the police station -- the sirens wailing.

Volunteers: What these arrested suspects had done was to answer a local newspaper ad calling for volunteers in a study of the psychological effects of prison life. We wanted to see what the psychological effects were of becoming a prisoner or prison guard, in a simulated prison. The applicants from the U.S. and Canada were given diagnostic interviews and personality tests to eliminate candidates with psychological problems, medical disabilities, or a history of crime or drug abuse, and would earm $15/day by participating in the study. It is important to remember that at the beginning of our experiment there were no differences between boys assigned to be a prisoner and boys assigned to be a guard.

Constructing the Experiment :To help us closely simulate a prison environment, our prison was constructed by boarding up each end of a corridor in the basement of Stanford's Psychology Department building. That corridor was "The Yard" and was the only outside place where prisoners were allowed to walk, eat, or exercise, except to go to the toilet down the hallway. On the side of the corridor opposite the cells was a small closet which became "The Hole," or solitary confinement. An intercom system buged the cells and was used for public announcement. There were no windows or clocks to judge the passage of time, which later resulted in some time-distorting experiences.

Arrival: Blindfolded and in a state of mild shock The prisoners were brought into our jail one at a time.Each prisoner was systematically searched and stripped naked, and deloused with a spray, to convey our belief that he may have germs or lice; a degradation procedure designed in part to humiliate prisoners. The prisoner was then issued a uniform -- a dress, or smock, which each prisoner wore at all times with no underclothes and an ID number on front and back. -- Real male prisoners don't wear dresses, but they do feel humiliated and emasculated. The number was to minimize each persons individuality. Each prisoner also wore a bolted, heavy chan on his right ankle -- not common in prisons, but used to remind prisoners of the oppressiveness of their environment. Rubber sandals were the footware, and, a stocking cap on their head made from a woman's nylon stocking.

The cells were so small there was only room for three cots, on which the prisoners slept or set, with little room for anything else.

We began with nine guards and nine prisoners.

All guards were dressed in identical uniforms of khaki, and they carried a whistle around their neck and a billy club, and special Mirror sunglasses that prevented anyone from seeing their eyes or reading their emotions, promoting their anonymity. We were, of course, studying not only the prisoners but also the guards, who found themselves in a new power-laden role.

The first day passed without incident, but on the second day rebellion broke out. Now the problem was, what to do about this rebellion? The guards were angered and frustrated as the prisoners began to taunt and curse them. Psychological tactics began .The effect was to break the solidarity among prisoners.

Suddenly there was greater solidarity among the guards, and, it was no longer just an experiment, no longer a simple simulation, and every aspect of the prisoners' behavior fell under the total and arbitrary control of the guards.

Prisoner #8612 began suffering from acute emotional disturbance, disorganized thinking, uncontrollable crying, and rage. When he began to act "crazy," to scream, to curse, to go into a rage that seemed out of control. We became convinced that he was really suffering and that we had to release him.

I was sitting there all alone when who should happen along but a colleague and former Yale graduate student roommate, Gordon Bower. Gordon had heard we were doing an experiment, and he came to see what was going on. I briefly described what we were up to, and Gordon asked me a very simple question: "Say, what's the independent variable in this study?"

To my surprise, I got really angry at him. The security of my men and the stability of my prison was at stake, and now, I had to deal with this bleeding-heart, liberal, academic, effete dingdong who was concerned about the independent variable! It wasn't until much later that I realized how far into my prison role I was at that point -- I was thinking like a prison superintendent rather than a research psychologist. NOTE: What are the dangers of the principal investigator assuming the role of prison superintendent?

We had heard a rumor of a prison break but it never materialized. How did we react to this mess? With considerable frustration and feelings of dissonance over the effort we had put in to no avail. Someone was going to pay for this. The guards again escalated, very noticeably their level of harassment, forcing the prisoners to do menial, repetitive work such as cleaning out toilet bowls with their bare hands, do push-ups, jumping jacks, and increased the length of their counts to several hours each.

I invited a Catholic priest to evaluate how realistic our prison situation was. He interviewed each prisoner individually, and I watched in amazement as half the prisoners introduced themselves by number rather than name. The priest's visit further blurred the line between role-playing and reality.

Prisoner #819, was feeling sick, refused to eat, and wanted to see a doctor. He was persuaded to come out of his cell and while talking to us, he broke down and began to cry hysterically, just as had the other two boys we released earlier. I took the chain off his foot, the cap off his head, and told him to go and rest in a room that was adjacent to the prison yard. I said that I would get him some food and then take him to see a doctor. One of the guards lined up the other prisoners and had them chant aloud: "Prisoner #819 is a bad prisoner. They shouted this statement in unison a dozen times. I raced back to the room where I had left him, and what I found was a boy sobbing uncontrollably. The chanting was marked by utter confomity and compliance, as if a single voice saying, "#819 is bad."

Parole Board:The Board was composed mainly of people who were strangers to the prisoners (departmental secretaries and graduate students) and was headed by our top prison consultant.
Several remarkable things occurred during these parole hearings: First, when we asked prisoners whether they would forfeit the money they had earned up to that time if we were to parole them, most said yes. Then, when we ended the hearings by telling prisoners to go back to their cells while we considered their requests, every prisoner obeyed, even though they could have obtained the same result by simply quitting the experiment. Why did they obey? Because they felt powerless to resist. Their sense of reality had shifted, and they no longer perceived their imprisonment as an experiment.

By the fifth day: A new relationship had emerged between prisoners and guards. The guards now fell into their job more easily -- a job which at times was boring and at times was interesting.
The guards appeared to thoroughly enjoy the power they wielded, yet none of our preliminary personality tests were able to predict this behavior.

NOTE: In 2003 U.S. soldiers abused Iraqi prisoners held at Abu Ghraib, 20 miles west of Baghdad. The prisoners were stripped, made to wear bags over their heads, and sexually humiliated while the guards laughed and took photographs.
How could the guards move so readily into their roles? How could intelligent, mentally healthy, "ordinary" men become perpetrators of evil so quickly?

Prisoners' Coping Styles:Prisoners coped with their feelings of frustration and powerlessness in a variety of ways. At first, some prisoners rebelled or fought with the guards. Four prisoners reacted by breaking down emotionally as a way to escape the situation. One prisoner developed a psychosomatic rash over his entire body when he learned that his parole request had been turned down. Others tried to cope by being good prisoners, doing everything the guards wanted them to do. By the end of the study, the prisoners were disintegrated, both as a group and as individuals. There was no longer any group unity; just a bunch of isolated individuals hanging on, much like prisoners of war or hospitalized mental patients.

The guards had won total control of the prison, and they commanded the blind obedience of each prisoner.

One Final Act of Rebellion : Prisoner #416 coped by going on a hunger strike to force his release. After several unsuccessful attempts to get #416 to eat, the guards threw him into solitary confinement for three hours, even though their own rules stated that one hour was the limit. Still, #416 refused. At this point #416 should have been a hero to the other prisoners. But instead, the others saw him as a troublemaker. The head guard then exploited this feeling by giving prisoners a choice. They could have #416 come out of solitary if they were willing to give up their blanket, or they could leave #416 in solitary all night. NOTE: Most elected to keep their blanket and let their fellow prisoner suffer in solitary all night. (We intervened later and returned #416 to his cell.)

On the fifth night, at this point it became clear that we had to end the study. We had created an overwhelmingly powerful situation -- a situation in which prisoners were withdrawing and behaving in pathological ways, and in which some of the guards were behaving sadistically. Even the "good" guards felt helpless to intervene, and none of the guards quit while the study was in progress. Indeed, it should be noted that no guard ever came late for his shift, called in sick, left early, or demanded extra pay for overtime work.

I ended the study prematurely for two reasons:
, we had learned through videotapes that the guards were escalating their abuse of prisoners in the middle of the night when they thought no researchers were watching and the experiment was "off." Their boredom had driven them to ever more pornographic and degrading abuse of the prisoners.

, Christina Maslach, a recent Stanford Ph.D. brought in to conduct interviews with the guards and prisoners, strongly objected when she saw our prisoners being marched on a toilet run, bags over their heads, legs chained together, hands on each other's shoulders. 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. Once she countered the power of the situation, however, it became clear that the study should be ended.

After only six days
, our planned two-week prison simulation was called off.

On the last day, we held a series of encounter sessions, first with all the guards, then with all the prisoners (including those who had been released earlier), and finally with the guards, prisoners, and staff together. We did this in order to get everyone's feelings out in the open, to recount what we had observed in each other and ourselves, and to share our experiences, which to each of us had been quite profound.

In the encounter sessions, all the prisoners were happy the experiment was over, but most of the guards were upset that the study was terminated prematurely.

Two months after the study, here is the reaction of prisoner #416, our would-be hero who was placed in solitary confinement for several hours:"I began to feel that I was losing my identity, that the person that I called "Clay," the person who volunteered to go into this prison -- still is a prison to me. I don't regard it as an experiment or a simulation -- it was a prison run by psychologists instead of the state. I began to feel that identity, the person that I was, that had decided to go to prison was distant from me -- was remote until finally I was 416. I was really my number"

Compare his reaction to that of the following prisoner who wrote to me from an Ohio penitentiary after being in solitary confinement for an inhumane length of time: "I was recently released from solitary confinement after being held therein for thirty-seven months. The silence system was imposed upon me and if I even whispered to the man in the next cell resulted in being beaten by guards, sprayed with chemical mace, black jacked, stomped, and thrown into a strip cell naked to sleep on a concrete floor without bedding, covering, wash basin, or even a toilet....I know that thieves must be punished, and I don't justify stealing even though I am a thief myself. But now I don't think I will be a thief when I am released. No, I am not rehabilitated either. It is just that I no longer think of becoming wealthy or stealing. I now only think of killing -- killing those who have beaten me and treated me as if I were a dog. I hope and pray for the sake of my own soul and future life of freedom that I am able to overcome the bitterness and hatred which eats daily at my soul. But I know to overcome it will not be easy."

Terminated on August 20, 1971:After observing our simulated prison for only six days, we could understand how prisons dehumanize people, turning them into objects and instilling in them feelings of hopelessness.

And as for guards, we realized how ordinary people could be readily transformed from the good Dr. Jekyll to the evil Mr. Hyde.

In the decades since this experiment took place, prison conditions and correctional policies in the United States have become even more punitive and destructive, with more Americans -- some who are innocent -- in prisons than ever before.