The Stanford prison experiment (SPE) was a social psychology experiment that attempted to investigate the psychological effects of perceived power, focusing on the struggle between prisoners and prison officers.
It was conducted at Stanford University on the days of August 14–20, 1971, by a research group led by psychology professor Philip Zimbardo using college students. In the study, volunteers were assigned to be either “guards” or “prisoners” by the flip of a coin, in a mock prison, with Zimbardo himself serving as the superintendent. Several “prisoners” left mid-experiment, and the whole experiment was abandoned after six days. Early reports on experimental results claimed that students quickly embraced their assigned roles, with some guards enforcing authoritarian measures and ultimately subjecting some prisoners to psychological torture, while many prisoners passively accepted psychological abuse and, by the officers’ request, actively harassed other prisoners who tried to stop it. The experiment has been described in many introductory social psychology textbooks, although some have chosen to exclude it because its methodology is sometimes questioned.
The U.S. Office of Naval Research funded the experiment as an investigation into the causes of difficulties between guards and prisoners in the United States Navy and United States Marine Corps. Certain portions of it were filmed, and excerpts of footage are publicly available.
Some of the experiment’s findings have been called into question, and the experiment has been criticised for unscientific methodology and possible fraud. Although Zimbardo interpreted the experiment as having shown that the “prison guards” instinctively embraced sadistic and authoritarian behaviours, Zimbardo actually instructed the “guards” to exert psychological control over the “prisoners”. Critics also noted that some of the participants behaved in a way that would help the study, so that, as one “guard” later put it, “the researchers would have something to work with,” which is known as demand characteristics. Variants of the experiment have been performed by other researchers, but none of these attempts have replicated the results of the SPE.