Philip Zimbardo, the psychologist behind the controversial “Stanford Prison Experiment” intended to examine the psychological experiences of imprisonment, has died at 91. In the 1971 prison study, Zimbardo and graduate students recruited college-aged males to spend two weeks in a mock prison in the basement of a building on the Stanford campus, the Associated Press reports. The study, intended to last two weeks, ended after six days as the students playing guards became psychologically abusive and those playing prisoners became anxious, emotionally depressed and enraged, Stanford said.
The university said that "as the experiment progressed, conditions rapidly deteriorated, and the line between role-playing and reality collapsed. The outcome, as Zimbardo acknowledged, was “shocking and unexpected" and "out-of-control." Some guards became tyrannical and abusive in their behavior toward prisoners. Zimbardo was criticized for taking the role of superintendent – becoming an active participant in the study and no longer a neutral observer. Zimbardo was considered a leading expert on the bystander effect, the theory that in the presence of others, individuals are less likely to step in and help someone in need.