What happens when you put good people in a bad place?

That was the question that an experiment in 1971 set out to answer when Stanford University professor and psychologist Philip Zimbardo used funding provided by the U.S. Office of Naval Research to create a make-believe prison in the basement of a university building. Male students were offered the chance to take part in the two-week experiment (and to make $15 per day). All applicants were carefully screened to ensure that they were healthy, emotionally and psychologically stable. 24 men were selected out of 75 that had applied. These men were then randomly assigned to play the role of either prisoners or guards in the “prison.”

Initially, nobody was particularly concerned: after all, these were stable, intelligent young men who understood that they would be playing a role for just two weeks. Some people even considered that the experiment was pointless because everyone involved knew that they were simply acting roles for a limited time, so they couldn’t be expected to behave in the ways that real prisoners and guards did.

Nonetheless, the experiment began on August 15th, 1971, and just six days later, on August 20th, it was abruptly and unexpectedly terminated after the “guards” had become brutal and sadistic and the “prisoners” had become withdrawn, fearful, and apathetic. There were real concerns that someone might end up being seriously hurt or suffer long-term psychological damage.

How could a group of nice, healthy, intelligent young men suddenly transform into sadistic thugs? How could another equally intelligent group of young men suddenly become apathetic victims of this brutality? What did this say about the malleability of human behavior, even when everyone involved knew that this wasn’t real?