The Stanford Prison Experiment

In August 1971, a social psychology study designed by a team at Stanford University to investigate the effects of role-playing, labelling, and social expectations on behaviour within a simulated prison environment took place (Encyclopaedia Britannica, 2025b; Sturt, 2000; Zimbardo et al., 1999). Known as The Stanford Prison Experiment, the study - funded by the US Navy research arm and led by Professor Phillip Zimbardo - set out to find how ordinary people, when placed in positions of power or powerlessness, would behave (Sturt, 2000).

The study participants were 24 physically and mentally healthy, "intelligent middle-class" male university students, recruited from a pool of 70 initial applicants (Sturt, 2005, p. 1; Zimbardo et al., 1999). Before the study proper began, participants were randomly assigned to 'prisoner' or 'guard' roles (Sturt, 2000).

The prisoner participants were 'arrested' by local police, brought to a prison (mocked up from basement offices in the Stanford psychology building), and made to wear smocks, chains, and stocking caps to simulate the dehumanising experience of prison. The guards, dressed in khaki uniforms and equipped with mirrored sunglasses to prevent eye contact, were instructed to maintain order but were not supposed to use physical violence (Sturt, 2000; Zimbardo et al., 1999).

Very quickly, guard participants began to exhibit authoritarian behaviour and cruelty, while prisoner participants showed signs of extreme stress and emotional breakdown. On the second day, prisoner participants staged a rebellion, averted by the guard participants using divide and rule, with a 'privilege cell' for those who complied. This increased participant distrust and broke prisoner participant solidarity. Guard participant abuse escalated, particularly during night shift where they believed they were not being monitored. Guard participants forced prisoner participants to perform humiliating tasks (e.g. bare-hand toilet cleaning; sleep deprivation; constant harassment) (Encyclopaedia Britannica, 2025b; Sturt, 2005; Zimbardo et al., 1999).

Almost immediately, the study was outside research ethics parameters. Three prisoners were released early due to severe emotional distress; others showed signs of psychological trauma. The situation became so extreme that an outside observer and recent PhD graduate, Christina Maslach, challenged the study's ethics. Her intervention led to Professor Zimbardo ending the experiment on day six of the planned fourteen day programme (Sturt, 2000; Zimbardo et al., 1999).

Widely criticised for ethical violations and methodological flaws, the study lacked proper controls, with participant behaviour possibly influenced by demand characteristics or individual personality traits (Encyclopaedia Britannica, 2025b). Later studies, such as the BBC Prison Study (Patricia Im, 2017), challenged some of the Zimbardo's findings, suggesting that the guards' behaviour was not inevitable but rather a result of specific situational dynamics (Encyclopaedia Britannica, 2025b). Zimbardo has defended the study, claiming it demonstrated the power of situational forces over individual behaviour (Zimbardo et al., 1999).

The study has made room for conversations about ethical prisoner treatment and prison environment reform, including (Zimbardo et al., 1999):

• Power of Situations: demonstrating how situational forces can override individual dispositions, leading ordinary people to commit acts of cruelty or submit to abuse
• Role Internalisation: participants quickly internalised their assigned roles, with guards becoming authoritarian and prisoners becoming submissive and distressed
• Ethical Boundaries: important ethical questions were raised about psychological research limits and the responsibility of researchers to do no harm to participants
• Institutional Dehumanisation: institutional environments, such as prisons, can strip individuals of their humanity, leading to harmful behaviours.

Controversial and influential, the Stanford Prison Experiment illustrated the importance of ethical research practices, and the potential for the abuse of power. Behaviour is not solely driven by individual personality traits; situational awareness is also an important factor in understanding human behaviour (Sturt, 2000; Zimbardo et al., 1999). The abuse of prisoners at Abu Ghraib was reasonably foreseeable if we consider the Stanford Prison study findings (Encyclopaedia Britannica, 2025a).

I am sure the Stanford Prison Experiment will continue to influence research ethics and power for a while yet.

Sam

References:

Encyclopaedia Britannica. (2025a). Abu Ghraib prison. https://www.britannica.com/topic/Abu-Ghraib-prison

Encyclopaedia Britannica. (2025b). Stanford Prison Experiment. https://www.britannica.com/event/Stanford-Prison-Experiment

Patricia Im. (2017, January 10). Psychology: The Stanford Prison Experiment - BBC Documentary []. YouTube. https://youtu.be/F4txhN13y6A

Sturt, G. (2000). Zimbardo: A Study of Prisoners and Guards in a Simulated Prison. Craig Haney, Curtis Banks and Philip Zimbardo (1973). A Simulation Study of the Psychology of Imprisonment: Conducted at Stanford University. http://www.garysturt.free-online.co.uk/zimbardo.htm

Zimbardo, P. G. (2007). Revisiting the Stanford Prison Experiment: a Lesson in the Power of Situation. The Chronicle of Higher Education, 53(30), B6-7. https://www.chronicle.com/article/revisiting-the-stanford-prison-experiment-a-lesson-in-the-power-of-situation/