The Stanford prison experiment was ostensibly a psychological study of human responses to captivity and its behavioral effects on both authorities and inmates in prison. It was conducted in 1971 by a team of researchers led by Philip Zimbardo of Stanford University. Undergraduate volunteers played the roles of both guards and prisoners living in a mock prison in the basement of the Stanford psychology building. Within one day things got out of hand, and the "guards" used unmonitored brute force on many of the inmates. The experiment was cancelled after 6 days instead of the planned 14.