The Stanford prison experiment was a study of the psychological effects of becoming a prisoner or prison guard. The experiment was conducted in 1971 by a team of researchers led by Psychology Professor Philip Zimbardo at Stanford University. Twenty-four undergraduates were selected out of 70 to play the roles of both guards and prisoners and live in a mock prison in the basement of the Stanford psychology building. Roles were assigned at random. They adapted to their roles well beyond that expected, leading the guards to display to authoritarian and even draconian measures. Two of the prisoners were upset enough by the process to quit the experiment early, and the entire experiment was abruptly stopped after only six days. The experimental process and the results remain controversial. The entire experiment was filmed, with excerpts soon made publicly available, leaving some disturbed by the resulting film. Over 30 years later, Zimbardo found renewed interest in the experiment when the Abu Ghraib torture and prisoner abuse scandal occurred............
The experiment quickly grew out of hand. Prisoners suffered — and accepted — sadistic and humiliating treatment from the guards. The high level of stress progressively led them from rebellion to inhibition. By the experiment's end, many showed severe emotional disturbances............
The Stanford experiment ended on August 20, 1971, only six days after it began instead of the fourteen it was supposed to have lasted. That day, Zimbardo called both the guards and inmates to a meeting and announced that the 'prison' was closing down. The experiment's result has been argued to demonstrate the impressionability and obedience of people when provided with a legitimizing ideology and social and institutional support. It is also used to illustrate cognitive dissonance theory and the power of authority.
The results of the experiment are said to support situational attribution of behaviour rather than dispositional attribution. In other words, it seemed the situation caused the participants' behaviour, rather than anything inherent in their individual personalities. In this way, it is compatible with the results of the also-famous Milgram experiment, in which ordinary people fulfilled orders to administer what appeared to be damaging electric shocks to a confederate of the experimenter.
Shortly after the study had been completed, there were bloody revolts at both the San Quentin and Attica prison facilities, and Zimbardo reported his findings on the experiment to the U.S. House Committee on the Judiciary.