Human Behavior Experiments The Mock Prison

About a human behavior experiment done by Dr. Zimbardo of Stanford University, scientific research on the effects of confinement on guards and prisoners.


A 2nd experiment, conducted by Dr. Philip G. Zimbardo, of Stanford University, Calif., tested a slightly different aspect of roles and the effect they have on people's behavior. In his experiment, unlike Rosenhan's, no one was duped. All participants were fully informed of the nature and details of the experiment. Even so, the results were so extreme that the experiment had to be terminated after 6 days of the 14 days originally scheduled.

The Zimbardo experiment involved setting up a mock prison and assigning volunteers to be either prisoners or guards. The prison was set up in the Stanford psychology building. Volunteers were chosen from among male students in the Palo Alto area after carefully screening them for any psychological or physical problems. They were then randomly assigned to be prisoners or guards. Zimbardo himself served as superintendent.

Prisoners were subjected to strict discipline. The moment they entered the mock prison, their personal belongings were taken away, they were given loose smocks to wear, and they were assigned to bare cells. They received stocking caps to wear over their hair to simulate the shaved heads of real prisoners. They had to ask permission to write letters, smoke, or go to the bathroom, and were deprived of showers, windows, and outdoor exercise.

Those assigned to be guards were depersonalized as well. They wore identical khaki uniforms and silver reflector sunglasses. Their only instructions were to maintain law and order, and to do so they were issued billy clubs, whistles, and handcuffs.

The 2nd morning the prisoners staged a riot. The guards responded by hosing them with chilling carbon dioxide and stripping them. The guards also devised a "good prisoner cell" with special privileges, to divide and confuse the inmates.

As time went on, guards became more domineering and abusive and began devising degrading, tedious tasks for the prisoners. The prisoners responded by becoming meek and passive after their initial defiance. They became nonsupportive of each other and, in post-experimental interviews, were overwhelmingly deprecative of fellow prisoners.

Despite the fact that all the participants knew they were merely acting in an experiment, all took their roles quite seriously. Guards pressured one another to use their power to abuse the prisoners, often to the point of cruelty. The occasional kind guard was looked upon as a sissy, and never once in the experiment did a kind guard try to restrain even the most sadistic guard or remind him that they were just part of an experiment.

The prisoners also took their parts quite seriously. One had to be released the 3rd day for severe depression; another developed a psychosomatic rash over most of his body. A total of 5 had been released by the 6th day, at which time the experiment was terminated because of the severity of the participants' reactions. At the outset, Zimbardo had feared that 2 weeks would prove too short a time to simulate real prison conditions; he found that 6 days were more than enough. He demonstrated in a short time how vulnerable people are to assigned roles and to acting as they think they are supposed to act, even in direct conflict with how they feel inwardly. He also verified certain suspicions about the American prison system. The experiment leads one to pause and consider the more subtle consequences of roles that are less consciously assumed, and which one takes on for a longer time. Zimbardo also explicitly points to the "prisons" of racism and sexism in which we all reside.

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