The Stanford Prison Experiment was conducted by psychologist Philip Zimbardo between August 15 and 21, 1971, to explore how social roles and situational forces can influence human behavior.
Twenty-four psychologically healthy male students from Stanford University were randomly assigned to play the roles of guards or prisoners in a mock prison set up in the basement of the university’s psychology building.
The study was intended to last two weeks. However, it was terminated after just six days due to the rapid escalation of psychological distress among prisoners and abusive behavior among guards.
What began as a simulation quickly spiraled into an ethical and psychological crisis—forever changing the discourse on power, conformity, and ethics in research.
What Occurred During The Experiment
According to Zimbardo’s accounts, participants internalized their assigned roles with alarming speed.
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Guards began exhibiting authoritarian, aggressive, and dehumanizing behavior, enforcing arbitrary punishments and creating a pervasive sense of fear.
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Prisoners, conversely, became passive, anxious, and emotionally unstable.
Several participants experienced emotional breakdowns and had to be released early, despite being screened as mentally healthy prior to the experiment.
Zimbardo concluded that ordinary individuals, when placed in environments of unequal power, could be driven to commit cruelty. The results suggested that situational pressures, rather than inherent personality traits, could explain behaviors of oppression or submission.
This interpretation aligned with the emerging body of work on obedience and authority, such as Stanley Milgram’s 1960s experiments on compliance.
Recent Criticism And Ethical Debate
Despite its iconic status in psychology, the Stanford Prison Experiment has faced intense scrutiny over the past two decades.
Modern researchers argue that its methodological flaws and ethical violations make it a poor model of scientific validity.
A 2019 article in American Psychologist called the study “an incredibly flawed experiment that should have died an early death.”
French researcher Thibault Le Texier’s archival investigation revealed several concerning details:
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Zimbardo and his team allegedly influenced the behavior of participants by providing specific guidance to guards during their orientation.
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The study was not double-blind — participants were aware of expected outcomes.
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Several rules and methods were copied from an earlier Stanford project, the Toyon Hall Experiment, which Zimbardo did not credit in subsequent publications.
These revelations suggested that the so-called spontaneous transformation of participants into cruel guards and submissive prisoners may have been constructed or exaggerated rather than a genuine product of situational dynamics.
Zimbardo’s Response
Zimbardo has defended the integrity of his experiment for decades.
He maintains that the guards were given only minimal instructions: to maintain order, avoid physical violence, and create a believable prison environment.
According to Zimbardo:
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The escalation of cruelty arose organically following a prisoner rebellion on the second day, demonstrating the corrupting power of authority, not researcher influence.
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While some guards became abusive, others remained fair or passive, proving that individual choice still mattered within situational constraints.
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Allegations that a guard nicknamed “John Wayne” was merely acting out a movie stereotype were dismissed; Zimbardo argued that his humiliating behaviors far exceeded performance or parody.
Regarding the claim that one prisoner, Doug Korpi, faked a breakdown to leave for exams, Zimbardo responded that researchers have an ethical obligation to treat all distress as genuine.
Korpi himself later stated that the experience was deeply upsetting, lending credibility to Zimbardo’s belief that the study induced real psychological harm.
Conclusion: Power, Pressure, And The Human Psyche
The Stanford Prison Experiment remains one of the most influential and controversial psychological studies ever conducted.
Its findings continue to provoke discussion about the fragility of morality under authority, the power of social roles, and the limits of ethical experimentation.
While some view it as a powerful demonstration of situational influence, others regard it as a flawed performance shaped by researcher expectations.
Regardless of interpretation, the experiment stands as a cautionary tale — both about the human capacity for cruelty and the ethical boundaries of psychological research.
References
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Le Texier, T. (2019). Debunking the Stanford Prison Experiment. American Psychologist, 74(7), 823–839. https://doi.org/10.1037/amp0000401
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Zimbardo, P. (n.d.). Philip Zimbardo’s response to recent criticisms of the Stanford Prison Experiment. Stanford Prison Experiment. Retrieved October 30, 2025, from https://www.prisonexp.org/response
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Zimbardo, P. (1983). To Control a Mind. Stanford Magazine, 11, 59–64.