It began with an ad in the classifieds.
Male college students needed for psychological study of prison life. $15 per day for 1-2 weeks. More than 70 people volunteered to take part in the study, to be conducted in a fake prison housed inside Jordan Hall, on Stanford's Main Quad. The leader of the study was 38-year-old psychology professor Philip Zimbardo. He and his fellow researchers selected 24 applicants and randomly assigned each to be a prisoner or a guard.