Zimbardo is perhaps best known as the creator of the Stanford Prison Experiment. Here, for the first time and in detail, he tells the full story of this landmark study, in which a group of college-student volunteers was randomly divided into “guards” and “inmates” and then placed in a mock prison environment. Within a week the study was abandoned, as ordinary college students were transformed into either brutal, sadistic guards or emotionally broken prisoners.

By illuminating the psychological causes behind such disturbing metamorphoses, Zimbardo enables us to better understand a variety of harrowing phenomena, from corporate malfeasance to organized genocide to how once upstanding American soldiers came to abuse and torture Iraqi detainees in Abu Ghraib.