Stanford Prison Experiment

Study Design and Findings

The SPE was conducted in 1971 by a group of Stanford research psychologists, led by Philip Zimbardo, and his two graduate students, Craig Haney and Curtis Banks. The experiment was designed to control for the individual personality variables (e.g., narcissism, authoritarianism) that are sometimes used to attempt to explain behavior in prison and other institutional settings. That is, the researchers in the SPE neutralized the explanatory argument that pathological traits alone accounted for extreme and abusive behavior in severe institutional setting such as prisons. They did this by (a) selecting a group of participants who were psychologically healthy and had scored in the normal range of numerous personality variables and (b) assigning participants to the role of either prisoner or guard on a completely random basis. The behavior that resulted when these otherwise healthy, normal participants were placed in the extreme environment of a simulated prison would therefore have to be explained largely if not entirely on the basis of the characteristics of the social setting in which they had been placed.

The setting itself was designed to be as similar as possible to an actual prison, given a number of obvious practical and ethical constraints. Constructed in the basement of the Psychology Department at Stanford University, the “Stanford County Prison” had barred doors on the small rooms that served as cells, cots on which the prisoners slept, a hallway area that was converted to a prison “yard” where group activities were conducted, and a small closet that served as a short-term “solitary confinement” cell for disciplining unruly prisoners. The prisoners wore uniforms that were designed to deemphasize their individuality and underscore their powerlessness. In contrast, guards donned military-like garb, complete with reflecting sun glasses and nightsticks. Guards generated a set of rules and regulations that in many ways resembled those in operation in actual prisons, and prisoners were expected to comply with the guards' orders. However, guards were instructed not to resort to physical force to gain prisoner compliance.

Despite the lack of any legal mandate for the “incarceration” of the prisoners, and despite the fact that both groups were told that they had been randomly assigned to their roles (so that, for example, guards knew that prisoners had done nothing to “deserve” their degraded prisoner status, and similarly, prisoners knew that the guards had no special training or actual legal authority over them), the behavior that ensued was remarkably similar to behavior that takes place inside actual prisons. It also was surprisingly extreme in intensity and effect. Thus, initial prisoner resistance and rebellion were met forcibly by guards, who quickly struggled to regain their power and then proceeded to escalate their mistreatment of prisoners throughout the study, at the slightest sign of affront or disobedience.

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