The Stanford Prison Experiment proved good people turn cruel when given power.
Verdict: contested
Archival evidence shows guards were coached and results shaped; it functions more as a demonstration than proof.
What the evidence shows
In 1971 Philip Zimbardo assigned students to be guards or prisoners in a mock basement prison; it was stopped after six days amid escalating abuse. The study became a textbook proof that situations, not dispositions, drive cruelty, and shaped decades of writing on power and evil.
Drawing on the study's own archives, recordings, and participant interviews, Le Texier (2019) documented that guards were explicitly encouraged to be tough, that a key 'breakdown' was partly performed, and that the study lacked controls, a real hypothesis test, and standardised measures. It was never a controlled experiment. The broader point — that roles and situations shape behaviour — has support from other work, but the Stanford study itself does not prove it; the strong 'anyone becomes a monster' claim is contested.
Sources
Haney, C., Banks, C., & Zimbardo, P. (1973). Interpersonal dynamics in a simulated prison.
International Journal of Criminology and Penology, 1, 69–97
Reported that participants rapidly conformed to abusive guard and submissive prisoner roles, framed as evidence of situational power.
Source →Le Texier, T. (2019). Debunking the Stanford Prison Experiment.
American Psychologist, 74(7), 823–839
Archival records show guards were coached toward cruelty and the study lacked the controls needed to prove its famous conclusion.
DOI: 10.1037/amp0000401 →