Zimbardo’s Stanford Prison Experiment

• What was the aim of this study?

  To measure the extent that people conform to a social role
• What was the procedure?

  • 24 psychologically sound ppts (emotionally stable) volunteered to be in the study.
  • 12 randomly assigned to be ‘prisoner’ - this was unknowlingly (deception) and were arrested for, their own homes and taken to a mock prison in the basement of Stanford university
• What happened to the prisoners when they arrived?

  • stripped, hosed down ( dehumanized ) and deloused (removal of mites and ticks)
  • given prison uniforms and a 10 digit number to be used instead of their names ( deinvidualisation )
• What happened to the guards when they arrived?

  • given uniform, baton (told not to use), handcuffs and sunglasses (hide emotion + avoid eye contact)
• How were participants told to behave?

  • prisoners told they couldn't leave, had to ask for parole
  • Guards told they have complete power but can't use the baton
  • Zimbardo played the role of superintendent to oversee the study, planned to last for 2 weeks, overt
• What were the results of Zimabrdo’s study ?

  • guards were enthusiastic and harsh
  • prisoners rebelled on day 2 - guards retaliated and because more harsh -> woke prisoners in the middle of the night for head counts, cleaning bathroom with their bare hands and Frankenstein role-play
  • Guards were so invested they worked overtime
  • Study shut down on day 6 due to extreme psychological distress
• What was the conclusion of the study?

  • social roles have a powerful influence on behaviour
  • Guards became brutal, prisoners became passive
• Study’s ethical issues - informed consent

  Deception used, prisoners weren't told they were going to be arrested from their homes
• Study’s ethical issues - Deception 


  Prisoners not told they would be arrested and taken to prison. However this was needed for natural behaviour
• Study’s ethical issues - Right to withdraw

  • prisoners were told they weren't allowed to leave, they would have to ask for parole leaving them feeling like they didn't have the right to withdraw
  • But this was needed for natural behaviour - prisoners can't leave in real life
• Study’s ethical issues - Potection from harm

  • extreme psychological distress was experienced in such a short time frame, so much so the study was shut down in day 6. Some guards used the baton on prisoners
  • Wasn't necessary but did show what was happening is the U.S. prisons at the time
• Study’s ethical issues - Privacy

  • prisoners privacy was invaded when they were stripped, deloused and watched 24 hrs a day and made to do dehumanizing tasks
  • Not needed for the study but did explain what was happening in U.S. prisons at the time.
• What participants were used?

  Male students, it ignores females - therefore the findings can only be used to explain males conformity to social roles
• What sampling was used?

  Volunteer. May have been highly motivated and have an interest in the topic
• Can this study be generalised to more than an individualistic culture and why?

  Should only be used to explain conformity to social roles in individualistc cultures not collectivist because it only uses American participants and settings.
• Research Method: 


  • controlled observation
  • Overt
  • Participant
  • Zimbardo played superintendent and lost sight of what was happening in his study
• One strength of the study

  All ppts were psychologically tested and were mentally sound - demonstrates the environment causes us to conform to social roles. This study and Asch’s line study lead to the development of Ethics in Psychology
• Weakness of the study

  Zimbardo exaggerated his findings:

  • only one third of the guards were harsh
  • 1/3 enforced the rules correctly
  • 1/2 were lenient to prisoners
• Real World Application

  Study can be used to explain human behaviour during war (crimes of war) e.g. Abu Ghraib- many high standing officers committed horrible acts on prisoners.