The lesser known truth about Zimbardo’s glorified Prison Life study

In 1973, Zimbardo, Haney and Banks[1] revealed to the world the extent to which ordinary people could conform and become cruel, merciless and vindictive in their infamous Stanford Prison Life Study. 22 male students were randomly assigned into two groups: prisoners and guards. Within hours of starting the experiment, the guards had adopted their roles and acted sadistically. The taunted prisoners were humiliated with insults. One prisoner (#8612 – prisoners were assigned numbers to further depersonalise them) was released after 36 hours due to uncontrollable fits of screaming, crying and anger! A study that was supposed to run for 14 days was terminated after just 6 days.
There are positives to Zimbardo’s study. The participants, middle-class college students, had answered a questionnaire about their familial history, physical and mental health background, behaviour, and had been deemed “normal”. The length screening process is advantageous as the study’s findings become more generalisable. Further, both quantitative and qualitative data was gathered adding to the validity of his research.
However, Zimbardo’s study into prison life is often glorified as a masterpiece in the world of Psychology. The study does, undoubtedly, give great insight into the horrors of what any ordinary person is capable of. With textbooks to news articles rationalising human behaviour using his study, are the results of the study really accurate?
Firstly, Zimbardo’s participants were a self-selected group who responded to a newspaper advertisement seeking volunteers for “a psychological study of prison life.”  These participants may have possessed certain characteristics that makes them more likely to volunteer, argues Carnahan and McFarland (2007).[2] In their laboratory experiment, they recreated the original advertisement and run a separate advertisement but this time without the phrase “prison life”. They found that people who thought they were going to participate in the prison life study had different dispositional characteristics. The ones who thought they were participating in the prison life study scored higher on levels of aggressiveness whilst scoring lower on measures of empathy. This is concurrent with Fromm (1973)’s[3] argument which states that Zimbardo is exaggerating the role of the situational hypothesis (the idea that the situation influences behaviour) and reducing the effects of personality (dispositional hypothesis)
Moreover, Banuazizi and Movahedi (1975)[4] pointed to evidence that suggested that the way the participants were acting was expected, based off stereotypes (e.g. guards acting in cruel ways) rather than conforming. Dave Eshelman, one of the guards, in a later interview stated that he had based his character on a character from the film Cool Hand Luke.[5] Zimbardo disputed this and pointed to evidence that the situation was very real to the participants. In a later study by Reicher and Haslam (2006)[6], the two psychologists wanted to repeat the experiment. Reicher and Haslam argued that the behaviour shown was due to the instructions given to them by Zimbardo. The rectify this, the guards were asked to come up with rules before the prisoners arrived and were told only to make the prison run smoothly. They came to a different conclusion that tyranny occurs due to the failure of groups rather than the conformity to roles!
Zimbardo’s use of nomothetic approach, where general laws have been made, can’t account for people who didn’t act ruthlessly. As discussed earlier, individual differences also determine the extent to which a person conforms to expected social roles. The behaviour of the guards varied, from extremely vile behaviour to guards who helped the prisoners and were described as “fair” and “nice”. Evidently, situational factors are not the only cause of conformity and dispositional factors also play a role. Perhaps future research should take an idiographic approach to account for these differences.

  1. Philip G. Zimbardo, Craig Haney, and Curtis Banks, \”A Study Of Prisoners And Guards\”, Naval Research Reviews, September 1973,,%20Naval%20Research%20Reviews.pdf.
  2. Thomas Carnahan and Sam McFarland, \”Revisiting The Stanford Prison Experiment: Could Participant Self-Selection Have Led To The Cruelty?\”, Personality And Social Psychology Bulletin 33, 5 (May 2007): 603–614,
  3. Erich Fromm, \”The Anatomy Of Human Destructiveness\”, Contemporary Sociology 3, 6 (November 1974): 513-515,
  4. William Dejong, \”Another Look At Banuazizi And Movahedi\’s Analysis Of The Stanford Prison Experiment\”. American Psychologist 30, 10 (October 1975): 1013-1015,
  5. Maria Konnikova, \”The Real Lesson Of The Stanford Prison Experiment\”. The New Yorker, June 12, 2015,
  6. Stephen Reicher and Alexander Haslam, \”Rethinking The Psychology Of Tyranny: The BBC Prison Study\”. British Journal Of Social Psychology 45, 1 (March 2006): 1-40,

About the Author
Allen Shaji, United Kingdom
Allen is a budding Geographer who is also keen on Psychology.  Allen likes to research topics stretching from Economics, to the brain, to the Environment and would like to go to university to further their knowledge.

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