The psychologist behind the controversial “Stanford prison experiment” used to study the psychology of evil dies at 91

() – Philip G. Zimbardo, the psychologist behind the controversial “Stanford prison experiment” that was intended to examine the psychological experiences of incarceration, has died at age 91.

Stanford University announced Friday that Zimbardo died Oct. 14 at his home in San Francisco. A cause of death was not provided.

In the 1971 prison study, Zimbardo and a team of graduate students recruited college-aged men to spend two weeks in a simulated prison in the basement of a building on the Stanford campus.

The study was terminated after six days, as students acting as guards became psychologically abusive and those acting as prisoners became anxious, depressed and enraged, according to the Stanford statement.

Zimbardo was criticized for assuming the role of jail superintendent, becoming an active participant in the study and no longer a neutral observer.

“The result of our study was shocking and unexpected,” I would write later Zimbardo along with one of the graduate students who was part of the project.

The experiment is currently used in psychology classes to study the psychology of evil and the ethics of psychological research with human subjects, Stanford said.

Zimbardo’s research also included persuasion, hypnosis, cults, shyness, time perspective, altruism and compassion, Stanford added.

Zimbardo is survived by his wife, Christina Maslach Zimbardo, three children and four grandchildren.