Philip Zimbardo

Philip Zimbardo is a social psychologist at Stanford University best known for conducting the Stanford Prison Experiment in 1971, a study that assigned healthy, psychologically normal male volunteers to the roles of guards and prisoners in a simulated prison environment in the basement of Stanford's psychology building. The experiment was halted after six days when guard behavior became sufficiently abusive and prisoner distress sufficiently acute that continuation was deemed unethical.¹

Stanford Prison Experiment

The experiment recruited college students through a newspaper advertisement and screened out anyone with psychological problems, criminal history, or medical conditions. The remaining volunteers were randomly assigned to be guards or prisoners. Prisoners were arrested at their homes by actual Palo Alto police officers, processed at a police station, transported to the simulated prison, stripped, deloused, given prison uniforms and numbers, and placed in cells. Guards were given uniforms, mirrored sunglasses, and nightsticks, and were told only that they were to maintain order.¹

Within days, guards began using psychological harassment tactics: forcing prisoners to perform degrading acts, denying bathroom privileges, disrupting sleep through random cell inspections, and using solitary confinement. Several prisoners showed acute emotional disturbances; one had to be released on the second day. A planned visitation by parents and friends proceeded as a staged performance, with the environment cleaned up and the prisoners coached. A prisoner who organized a resistance was isolated. Zimbardo, serving as superintendent of the simulated prison, became absorbed in maintaining the institution's operation until a colleague, Christina Maslach, observed the conditions and objected strenuously, prompting him to end the experiment after six days instead of the planned two weeks.¹

Methodological Criticism and Later Application

The Stanford Prison Experiment has been contested on methodological grounds. A 2018 investigation and subsequent scholarly examination found evidence that Zimbardo coached guards at the outset, that participants were aware of the experimental hypotheses, and that guard behavior was less spontaneously generated than the original accounts suggested. These critiques do not eliminate the experiment's basic finding that participants adapted rapidly to assigned roles, but they complicate the degree to which the study can bear the weight of broad claims about role-induced deindividuation.²

Zimbardo later applied the experiment's conceptual framework to analysis of the Abu Ghraib prison abuse photographs following the US invasion of Iraq, arguing in his 2007 book The Lucifer Effect that situational rather than dispositional factors explained the guards' behavior.¹