Philip Zimbardo conducted the Stanford Prison Experiment in 1971 to study the behaviors of people in a simulated prison environment. 24 male college students were selected and randomly assigned to be either guards or prisoners. The experiment was intended to last two weeks but had to be stopped after only six days. Both the "guards" and "prisoners" had quickly adapted their behaviors to fully embrace their artificial roles, with guards becoming increasingly cruel and prisoners descending into emotional distress. The experiment demonstrated how situational forces can override individual personality traits and lead ordinary people to act in extreme, sometimes abusive ways when given situational power over others.