The Stanford Prison Experiment, a dramatic simulation study of the psychology of imprisonment and one of the best known psychology experiments ever undertaken.Dr. Zimbardo takes us through the Stanford Prison Experiment, in which healthy college students are transformed into unstable prisoners and brutal prison guards within days by the power of the situation in which they found themselves.

In 1971, psychologist Philip Zimbardo and his colleagues set out to create an experiment that looked at the impact of becoming a prisoner or prison guard. Zimbardo, a former classmate of Stanley Milgram (who is best-known for his famous obedience experiment, was interested in expanding upon Milgram’s research. He wanted to further investigate the the impact of situational variables on human behavior.

The question the researchers asked was how would the participants react when placed in a simulated prison environment. “Suppose you had only kids who were normally healthy, psychologically and physically, and they knew they would be going into a prison-like environment and that some of their civil rights would be sacrificed. Would those good people, put in that bad, evil place—would their goodness triumph?” Zimbardo explained in one interview.

The researchers set up a mock prison in the basement of Standford University’s psychology building, and then selected 24 undergraduate students to play the roles of both prisoners and guards. The participants were selected from a larger group of 70 volunteers because they had no criminal background, lacked psychological issues, and had no major medical conditions. The volunteers agreed to participate for a one- to two-week period in exchange for $15 a day.

The simulated prison included three six by nine foot prison cells. Each cell held three prisoners and included three cots. Other rooms across from the cells were utilized for the prison guards and warden. One very small space was designated as the solitary confinement room, and yet another small room served as the prison yard.

The 24 volunteers were then randomly assigned to either the prisoner group or the guard group. Prisoners were to remain in the mock prison 24-hours a day for the duration of the study. Guards, on the other hand, were assigned to work in three-man teams for eight-hour shifts. After each shift, guards were allowed to return to their homes until their next shift. Researchers were able to observe the behavior of the prisoners and guards using hidden cameras and microphones.

While the Stanford Prison Experiment was originally slated to last 14 days, it had to be stopped after just six due to what was happening to the student participants. The guards became abusive and the prisoners began to show signs of extreme stress and anxiety. While the prisoners and guards were allowed to interact in any way they wanted, the interactions were generally hostile or even dehumanizing. The guards began to behave in ways that were aggressive and abusive toward the prisoners, while the prisoners became passive and depressed. Five of the prisoners began to experience such severe negative emotions, including crying and acute anxiety, that they had to be released from the study early. Even the researchers themselves began to lose sight of the reality of the situation. Zimbardo, who acted as the prison warden, overlooked the abusive behavior of the prison guards until graduate student Christina Maslach voiced objections to the conditions in the simulated prison and the morality of continuing the experiment.

“Only a few people were able to resist the situational temptations to yield to power and dominance while maintaining some semblance of morality and decency; obviously I was not among that noble class,” Zimbardo later wrote in his book The Lucifer Effect.

According to Zimbardo and his colleagues, the Stanford Prison Experiment demonstrates the powerful role that the situation can play in human behavior. Because the guards were placed in a position of power, they began to behave in ways they would not normally act in their everyday lives or in other situations. The prisoners, placed in a situation where they had no real control, became passive and depressed.