The Stanford prison experiment was ostensibly a psychological study of human responses to captivity and its behavioral effects on both authorities and inmates in prison. It was conducted in 1971 by a team of researchers led by Philip Zimbardo of Stanford University. Undergraduate volunteers played the roles of both guards and prisoners living in a mock prison in the basement of the Stanford psychology building.

Prisoners and guards rapidly adapted to their roles, stepping beyond the boundaries of what had been predicted and leading to dangerous and psychologically damaging situations. One-third of the guards were judged to have exhibited “genuine” sadistic tendencies, while many prisoners were emotionally traumatized and two had to be removed from the experiment early.

Ethical concerns surrounding the famous experiment often draw comparisons to the Milgram experiment, which was conducted in 1961 at Yale University by Stanley Milgram, Zimbardo’s former high school friend.

Tom Peters and Robert H. Waterman Jr wrote in 1981 that the Milgram Experiment in the 1960s and the later Zimbardo Experiment were frightening in their implications about the danger which lurks in the darker side of human nature.

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