Zimbardo prison experiment

In the Zimbardo prison experiment (Zimbardo, 1972, 1973; Zimbardo et al., 1973, 1974), male students were divided into two role-playing groups: guards and prisoners. Before the experiment, volunteer students were given personality tests, and only those in the “normal” range were chosen. Volunteers signed up for two weeks, and prisoners were told that they would be under surveillance and would have some civil rights suspended but that no physical abuse would be allowed. In a simulated prison in the basement of a Stanford University building, prisoners were deindividualized (dressed in standard uniforms and called only by their numbers) and guards were militarized (with uniforms, nightsticks, and reflective sunglasses). Guards were told to maintain a reasonable degree of order and served 8-hour shifts; prisoners were locked up 24 hours per day. Unexpectedly, the volunteers became too caught up in their roles. Prisoners became passive and disorganized, while guards became aggressive, arbitrary, and dehumanizing. By the sixth day, Zimbardo called off the experiment for ethical reasons. The risk of permanent psychological harm, and even physical harm, was too great.