Stanford professor Philip Zimbardo's infamous 1971 experiments

"Or consider Stanford professor Philip Zimbardo’s infamous 1971 experiments. Into a mock prison setting, he divided young people, who had tested “normal,” into prisoners and guards and dressed them for their roles. Zimbardo had designed the experiment to last two weeks, but on the sixth day he halted it. Using techniques eerily similar to those in Iraq’s Abu Ghraib prison decades later, the “guards” had begun brutalizing their “prisoners” causing severe emotional breakdown."

Philip Zimbardo, The Lucifer Effect: Understanding Why Good People Turn Evil (New York: Random House, 2007).