Stanford Prison Experiment (1971)

Philip Zimbardo assigned college students random roles as guards or prisoners in a simulated prison at Stanford University. Within days, guards became sadistic and prisoners broke down psychologically. The experiment was terminated after six days. It became a landmark study on the power of situational authority — but has been criticised for demand characteristics, coaching of guards, and Zimbardo's own role as prison superintendent, raising questions about whether the results are valid science at all.