Cognitive Connie
Understanding the stanford prison experiment
In August 1971, Philip Zimbardo and colleagues transformed the basement of the Stanford psychology department into a mock prison. Twenty-four healthy, psychologically screened male volunteers were randomly assigned to play "guards" or "prisoners" for what was planned as a two-week study. It was stopped after six days.
Key figures
Philip Zimbardo
1933–2024Social psychologist at Stanford who designed and ran the SPE, playing the role of prison superintendent himself. He subsequently became one of the foremost advocates of situationism in social psychology, testifying at court-martials following Abu Ghraib and publishing The Lucifer Effect (2007). He later founded the Heroic Imagination Project, focused on promoting "heroic" resistance to situational pressures toward harm.
Christina Maslach
1946–presentSocial psychologist (and Zimbardo's future wife) who visited the mock prison on Day 5 and was the first observer to mount a clear moral objection, confronting Zimbardo and prompting him to end the study the following morning. Her intervention became a key part of the SPE's legacy — cited as an example of individual moral courage overriding situational absorption. She is also widely known for her foundational research on burnout.
Craig Haney
1947–presentPsychologist who co-authored the original SPE paper with Zimbardo and has since become one of the leading researchers on the psychology of incarceration, applying the study's insights to prison reform advocacy and expert testimony on the effects of solitary confinement.
Key concepts
Situationism
The theoretical position that behaviour is primarily determined by situational and contextual factors rather than stable personality traits — the opposite of dispositionism. The SPE was designed to demonstrate situationism: by randomly assigning participants to roles, Zimbardo ensured that any differences in guard vs. prisoner behaviour could not be attributed to pre-existing personality differences, only to the role structure and institutional context. Lee Ross later named the failure to appreciate situational forces the "Fundamental Attribution Error."
Role theory and role absorption
Role theory holds that people's behaviour is substantially shaped by the social roles they occupy, which carry expectations, norms, and scripts. The SPE appeared to demonstrate rapid and profound role absorption: participants assigned as guards adopted aggressive, authoritarian behaviour within hours; participants assigned as prisoners became passive and distressed. Zimbardo himself showed role absorption as superintendent, losing his researcher perspective. However, the 2018 revelations about coaching complicate the spontaneity claim.
Deindividuation
A reduction in self-awareness and individual identity within a group or institutional context, typically facilitated by anonymity or uniform dress, which lowers inhibitions against anti-social behaviour. The SPE deliberately induced deindividuation in guards (identical uniforms, reflective sunglasses concealing eyes) and in prisoners (smocks, numbers replacing names, nylon caps). The uniforms were designed so that neither group would be identifiable as individuals — enabling harsher treatment of prisoners and reducing personal accountability in guards.
Dispositionism vs. situationism
Dispositionism attributes behaviour primarily to stable character traits ("bad apples"); situationism attributes it to contextual and structural factors ("bad barrels"). Zimbardo's key claim — developed in The Lucifer Effect (2007) — is that the SPE reveals the inadequacy of dispositional explanations for institutional abuse: it is the barrel that makes bad apples, not the individual apples who make bad barrels. Applied to Abu Ghraib, this framework frames guard behaviour as a systemic consequence of institutional conditions rather than individual pathology.
Ethical failures in the SPE
The SPE became a landmark in research ethics failures on multiple grounds: (1) Zimbardo's dual role as researcher and prison superintendent was a fundamental conflict of interest that prevented him from exercising appropriate oversight of participant welfare. (2) Participants were subjected to real psychological distress, humiliation, and deprivation. (3) No independent ethics oversight was in place. (4) The prisoner role was sufficiently total that genuine informed consent was impossible — participants could not anticipate what they were consenting to. The study would be impermissible under all modern institutional ethics frameworks.
The 2018 replication crisis and revelations
Journalist Ben Blum's 2018 investigation obtained audio recordings showing that Zimbardo's research assistant David Jaffe explicitly coached guards to be tough before the study began. The most "sadistic" guard, Dave Eshelman, publicly confirmed he had been consciously performing a character inspired by Cool Hand Luke rather than responding authentically to situational pressure. Prisoners who appeared to break down emotionally later stated they were partly performing — playing the role they thought was expected. These revelations do not disprove that the prison environment had psychological effects, but they severely undermine the claim that the behaviour emerged spontaneously from situational forces alone.
Modern relevance and applications
The SPE has been applied to Abu Ghraib (where Zimbardo testified as an expert witness), to corporate misconduct, and to the psychology of institutional power generally. Philip Zimbardo's TED Talk (2008) and The Lucifer Effect extended the SPE framework into a popular theory of evil. Despite methodological criticisms, the study's core insight — that institutional roles, power asymmetries, and anonymity can produce harmful behaviour in ordinary people — has remained influential in organisational psychology, prison reform advocacy, and the design of accountability structures.
Test your knowledge
Frequently asked questions
What happened in the Stanford Prison Experiment?+
24 healthy male volunteers were randomly assigned to be "guards" or "prisoners" in a mock prison in Stanford's psychology department basement. Guards quickly became authoritarian and abusive; prisoners became passive and distressed. Several prisoners experienced acute psychological disturbance. The study was planned for two weeks but was stopped after six days when Christina Maslach — a visiting researcher — confronted Zimbardo about what was being done to participants. Zimbardo himself later acknowledged he had become so absorbed in his role as prison superintendent that he had lost his perspective as a researcher.
Is the Stanford Prison Experiment accurate? Was it replicated?+
The SPE has faced significant methodological criticism, particularly following Ben Blum's 2018 investigation which found that guards had been coached to be tough before the study began, and that the most aggressive guard later confirmed he was consciously playing a character. These revelations undermine the central claim that behaviour emerged spontaneously from situational pressures. The study has not been directly replicated (ethical constraints prevent this), and a BBC Prison Study (Reicher & Haslam, 2006) using stricter methodology produced quite different findings — with guards failing to maintain tyranny and prisoners eventually organising. The SPE's influence has persisted more in popular culture than in current social psychology.
Why is the Stanford Prison Experiment considered unethical?+
The SPE violated research ethics principles on multiple fronts: participants experienced genuine psychological distress and humiliation; there was no independent ethics oversight; Zimbardo's dual role as researcher and superintendent prevented objective oversight of welfare; participants could not give truly informed consent because the psychological effects were not foreseeable; and the researchers failed to intervene even when distress was clearly visible. The study is now taught as a canonical example of research ethics failure, alongside the Milgram experiments, and it contributed to the strengthening of ethics review requirements for psychological research.
What did the Stanford Prison Experiment demonstrate about human nature?+
At face value, the SPE appeared to demonstrate that ordinary people rapidly adopt the behavioural norms associated with powerful or powerless social roles — that "good people" can do terrible things given the right (or wrong) situational context. This supported the situationist view that character is less stable than we assume, and that institutional structures rather than individual dispositions are the primary drivers of harmful behaviour. However, the 2018 revelations about coaching and performance complicate this reading. What the SPE more reliably demonstrates may be the malleability of people's behaviour to experimenter expectations and the risks of research designs that immerse the investigator in their own study.
Sources
Last reviewed July 2025- 1.
Haney C., Banks W.C., & Zimbardo P.G. (1973). Interpersonal dynamics in a simulated prison. International Journal of Criminology and Penology, 1(1), 69–97.
+About this source
Original published report of the Stanford Prison Experiment.
- 2.
Le Texier T. (2019). Debunking the Stanford Prison Experiment. American Psychologist, 74(7), 823–839.
+About this source
Archival analysis revealing methodological problems and experimenter coaching, substantially revising the standard interpretation.