Zimbardo (1971): Stanford Prison Experiment

• What was the aim of the Zimbardo's 1971 Stanford Prison experiment?


  To investigate conformity to social roles
• What was the sample for Zimbardo's 1971 Stanford Prison experiment?


  24 males, all:

  • Volunteers
  • Students
  • American
• What was the method for Zimbardo's 1971 Stanford Prison experiment?


  Controlled observation

  • Direct + through hidden cameras

  Lab experiment

  • Interviews conducted after study -> quantitative + qualitative data collected

  Set up as a roleplay
• What was the procedure of Zimbardo's 1971 Stanford Prison experiment?


  IV = roles of ppts, DV = behaviours exhibited by individuals + groups in response to assigned roles

  • Ppts psychologically tested prior to study + told their rights would be suspended
  • Mock prison in Stanford's basement
  • Prisoners 'arrested' by real police -> prison induction process + given smock/ID no., allowed certain rights
  • Guards given khaki uniforms/clubs/reflective glasses, told they had authority over prisoners = had to maintain 'law + order'
  • Physical violence from guards banned
  • Zimbardo = 'prison warden'
• What were the specific rights that the 'prisoners' were assigned in Zimbardo's 1971 Stanford Prison experiment?


  • 3 meals a day
  • 3 supervised toilet trips a day
  • 2 visits per week
• How long was Zimbardo's 1971 Stanford Prison experiment supposed to run for? When did it actually end?


  Planned to run for 2 weeks -> ended after 6 days
• What were the findings of Zimbardo's 1971 Stanford Prison experiment?


  • Took 2 hours for guards to start harassing prisoners
  • Prisoners rebelled -> guards punished them harshly = rebellion ended
  • Post-rebellion -> guards hostile towards prisoners = forced them to do humiliating chores to 'keep people in line'
  • Took 6 days for the guards to become so abusive the study had to end
  • Post-rebellion -> prisoners became passive towards guards' abuse; saw themselves as prisoners + acted as such
  • 5 prisoners released early due to extreme stress
• What were the conclusions of Zimbardo's 1971 Stanford Prison experiment?


  • Conformity to social roles via identification is brought about by situational factors
  • Changes to environment in prisons could decrease aggression levels
• What are the strengths of Zimbardo's 1971 Stanford Prison experiment?


  • Strong internal validity -> controlled observation + lab experiment
  • Differences between original study + BBC study = differing results -> not problems with original study
  • Real-life application = accurate theory
• What are the weaknesses of the Zimbardo's 1971 Stanford Prison experiment?


  • Cost-benefit analysis = study not worthwhile
  • Ethical issues = not replicable (BBC study)
  • Artificial environment = low mundane realism + external validity