What Did the Stanford Prison Experiment Show — The Critiques Raised Against the 'Situation Makes the Devil' Narrative

The textbook story of the Stanford Prison Experiment begins like this. In the summer of 1971, a mock prison was set up in the basement of the Stanford University psychology building. Ordinary college students were simply divided at random, like drawing straws, into "guards" and "prisoners," and within a few days, the guards reportedly became cruel and the prisoners broke down. The experiment, planned for two weeks, was stopped after six days. The lesson of this Stanford Prison Experiment (SPE) has often been summarized in a single sentence. It is that ordinary people, when placed in such a situation, become devils. This is the narrative of the myth that has spread for a long time, and how true it was is examined in the sections below.

For half a century, this sentence has been a regular fixture in textbooks. It is a powerful narrative that the root of human cruelty is not individual personality, but "the power of the situation." Philip Zimbardo, who led the experiment, recalled the experiment in detail in a 40th-anniversary interview within the context of his own career (PMID 22849005), and 25 years later, he even extended its lessons into proposals for reforming American correctional policy (PMID 9699456). Encyclopedias introduce the SPE as one of the most infamous social experiments in history (DOI: 10.1002/9781118845387.wbeoc176), handbooks treat it as an icon of psychology (DOI: 10.1093/obo/9780199828340-0269), and Zimbardo's The Lucifer Effect is placed in the research lineage of "the power of the situation" (DOI: 10.1002/9780470672532.wbepp149).

The SPE has been read, paired with Milgram's obedience experiment, as one of the two pillars of the "banality of evil" narrative. The banality of evil is the idea that ordinary people participate in atrocities without self-awareness, deliberation, or choice. The Milgram experiment is a study that observed how far participants would go in a task where they delivered electric shocks to another person upon the instruction of an authority figure. These studies have been accepted as evidence that humans passively conform to instructions from authority figures and given roles (PMID 23185132). There is also a perspective that reads the two experiments as a paired set (PMID 21322973).

However, there is another half to this story that has been obscured for a long time. This article traces how the myth was built, what dismantled it, and what more honest picture has taken its place. Counterarguments from Zimbardo's side are also covered.

Criticisms Left Out of Textbooks

Methodological criticisms of the SPE are not new. It is just that textbooks and classrooms have rarely covered those criticisms. In an analysis reviewing 14 introductory psychology books, only 2 books cited the theoretical and methodological problems of the SPE. Most books introduced only the interpretation of the "power of the situation," and they did not even mention the BBC prison study, which the analyzing authors view as more theoretically solid (DOI: 10.1177/1475725714568007). In another analysis, 11 out of 13 books covered the SPE, and among them only 6 mentioned even a single criticism (DOI: 10.1177/0098628314537968). The same pattern was repeated in social psychology textbooks (DOI: 10.1177/0098628314549703) and an online survey targeting introductory psychology instructors (DOI: 10.1177/0098628316636290). However, in the instructor survey, only ethical issues were covered relatively frequently, while theoretical and methodological criticisms were rare. Archival research diagnoses that because of this, it has been difficult for students and the public to know the fact that there are doubts about the validity of the SPE (PMID 31380664).

New Criticisms Raised Against the Myth — What the Archives Revealed

As Zimbardo's Stanford archives became publicly accessible, it became possible to look directly inside the experiment. One study relied on archival investigation and interviews with 15 participants not only to support existing criticisms, but to add new criticisms based on previously unknown facts (PMID 31380664). Most of the new criticisms in this section are claims from this single study, and the researchers themselves evaluate this as material that makes the scientific value of the SPE doubtful. The new criticisms are as follows. Data collection was biased and incomplete. The experiment adapted a prison experiment devised and conducted by students in Zimbardo's class 3 months prior. The guards received precise instructions regarding inmate treatment, and were not told that they were the subjects of research. There were also few instances where participants were fully immersed in the situation (PMID 31380664).

Among existing criticisms, a core one is demand characteristics, which are clues that let participants know what behavior the researcher expects, causing them to act accordingly. Pointed out as that clue in the SPE is the guard orientation held the day before the experiment started. At this gathering, the researchers conveyed expectations for hostile guard behavior. The principal investigator viewed the impact as small, but critics have suspected that the orientation became a 'script' for abuse. A study testing this suspicion presented a hypothetical mock prison study and asked participants to imagine they took on the guard role, having one group listen to the content of the SPE orientation and another group listen only to basic instructions. Across three experiments, the side that heard the SPE orientation expected more hostile and oppressive behavior from the researchers, other people, and themselves as guards. The authors interpret these results as giving empirical grounding to the suspicion that the language of the orientation sanctioned abuse. However, what was measured was not actual SPE participants, but the expectations of people who read hypothetical scenarios (PMID 30961456).

There is also evidence that the guards did not fall into their roles naturally. A study by Haslam's team analyzing archival materials comprehensively presents evidence that the experimenters directly urged the guards to accept their roles and act 'tough' (PMID 31380665). Identity leadership, which this study relies on as a basis, is when a leader leads people to believe that the cause of a certain group is noble and to believe that their behavior is necessary for that cause (PMID 31380665).

A study re-analyzing the behavior of 9 guards through unpublished records and interviews argues that the guards did not all fall into their roles in the same way. Viewed from the perspective that an individual's background and personality interact with the situation to create behavior, it suggests that the behavior of the three shift groups differed greatly depending on the influence group members exchanged with one another. This analysis puts forward the argument that some guards used role distancing—a strategy of drawing a line between oneself and the work demanded by the role—to protect themselves from coercive demands, while certain others experienced the role painfully encroaching on their ego (DOI: 10.1177/2632666320944316).

The sample itself may not have been random either. One study recruited participants for a study on "prison life" using newspaper advertisements nearly identical to the SPE's, and compared them with study participants recruited using the same advertisements except with the phrase "prison life" removed. Applicants for the prison study had higher aggression, authoritarianism, Machiavellianism (a tendency to use others for one's goals), narcissism, and social dominance orientation, and lower empathy and altruism (PMID 17440210). The authors state that while these results point toward an interpretation that views it as an interaction of person and situation rather than a pure "situation" explanation, what it actually means for the SPE remains a matter of speculation (PMID 17440210).

After the archives were opened, some psychologists demanded that the SPE be removed from lectures and textbooks. The authors of one paper agree with this demand, yet propose filling that spot with an SPE case study containing the facts revealed by the archives to teach students scientific thinking (DOI: 10.53841/bpsptr.2019.25.2.39).

An Alternative Paradigm — The BBC Prison Study

If people do not automatically slip into roles, what creates cruelty? An attempt to tackle this question head-on is the BBC Prison Study by Reicher and Haslam. This study is an experimental case study observing men divided randomly into prisoners and guards in a specially built facility for 8 days. The results differed from the narrative of the SPE. The guards failed to identify with their role. Identification is feeling that a certain group or person is "on my side" and acting as a member of it. The guards therefore hesitated to exercise authority and were eventually overpowered by the prisoners. The participants established an egalitarian social system for a while, and when that failed to last, there emerged a movement to establish an oppressive system, but resistance to this had grown weak (PMID 16573869).

The authors consider the key to be whether people identify with their assigned group, and what outcomes follow when they do or do not. In the new framework they put forward, a group's powerlessness and failure make it psychologically accepting of oppression (PMID 16573869). While social psychology has largely focused on the process of oppression, a review article takes the position that low-status groups bound by social identity, a shared self-perception of "I am a member of this group," can possess effective leadership and organization to fight authority and drive social change (PMID 21885855). A paper analyzing the BBC study data presents data supporting the proposition that prisoners' shared social identity enables leadership, and effective leadership in turn aids the development of identity (DOI: 10.1177/019027250707000204).

Zimbardo strongly criticized this study. Questioning the scientific legitimacy of research stemming from broadcasting company interests, he argued that there were biases, errors, and distortions (PMID 16573871). Reicher and Haslam counter-argued that this criticism employs three strategies. They stated that it shifts the debate to the narrow question of "how well prison conditions were replicated," conflates their scientific analysis with a TV program, and makes baseless attacks (PMID 16573872). Turner, caught up in this debate, evaluated in a separate commentary that the BBC study shakes the idea that people passively accept social roles (PMID 16573870). Haslam and Reicher's larger argument is this. Contrary to what the banality of evil says, perpetrators do not move without awareness or choice, but instead act thoughtfully, creatively, and with conviction (PMID 17440199).

Rereading Milgram — 'Identification', Not 'Obedience'

The twin of the SPE, Milgram's obedience experiment, has also been the subject of the same reinterpretation. The conventional wisdom is that participants blindly obeyed the orders of the experimenter, an authority figure, and continued the task of delivering electric shocks to another person. Milgram himself explained this as the agentic state, a state in which a person shifts the responsibility for their actions to an authority figure and merely carries out the authority figure's demands (PMID 26168469, PMID 30596731). On the other hand, the engaged followership model was proposed by Haslam, Reicher, and their colleagues, and most of the grounds for reinterpretation in this section also come from this research team. This model posits that participants did not passively follow instructions, but actively followed them by identifying with the leader's goals in order to achieve them. The degree to which a participant cooperates with the experimenter depends on how much they identify with the experimenter and the cause the experimenter represents, in this case, 'science' (PMID 26168469).

The evidence is concrete. Among the various 'prods' the Milgram experimenter used to encourage participants, the prod closest to a command was the least effective (DOI: 10.1111/josi.12072). A similar experiment that explored this further used a task where, instead of electric shocks, participants were asked to describe a progressively likable group using negative adjectives. The more the prods appealed to scientific goals, the more participants continued, whereas prods closer to commands tended to make them stop (DOI: 10.1111/josi.12072).

A study analyzing the Yale archives tackles another puzzle. The most prominent reaction of participants after the experiment was not distress, but a sense of happiness about having participated, and this is what requires explanation. The authors argue that this was the result of the experimenter making participants believe they were contributing to a progressive task, and they consider this analysis inconsistent with Milgram's agentic state model (PMID 25196821).

In a small-scale simulation study where 40 participants (20 in the control group) experienced a virtual reality Milgram situation, participants who identified more with science tried harder to help the learner, experienced less stress, and hesitated more before pressing the shock button. The authors interpret this as a rebuttal to the agentic state approach (PMID 30596731). A paper tracing the history of Milgram's research through archives describes how, before the famous first official result of 65% came out, Milgram went through several pilot experiments and carefully adjusted the procedure. The procedural adjustments continued until he was confident that a high completion rate would emerge (PMID 21366616). A review summarizing 50 years of research by the team that has championed the engaged followership model argues that Milgram's research should be reread not as evidence of 'blind conformity', but as an exploration of 'engaged followership' (DOI: 10.1146/annurev-lawsocsci-110316-113710). There are also criticisms coming from a different angle. One paper argues that Milgram's own position linking his experiment to Holocaust perpetration—namely, the stance that perpetrators were simply following orders—is not supported by his experimental results, and that this stance is effectively an 'obedience alibi' (DOI: 10.1515/auk-1998-0105).

Of course, this reinterpretation is not unanimous. Some researchers who analyzed Milgram's audio recordings acknowledge that the engaged followership theory is currently the most important explanation, but remain doubtful whether it actually operated in the manner and to the degree claimed by the theory. To them, 'obedience' is a phenomenon that allows for multiple empirical explanations, and engaged followership is just one of them (PMID 29527775). Just because the simple 'obedience' narrative has been shaken does not mean a single neat alternative narrative has taken its place.

The Honest Current State

The debate surrounding the SPE is not over. In 2020, Zimbardo's side and Haslam and Reicher's side squared off in the pages of an American Psychological Association journal. Zimbardo and Haney reaffirmed their stance that the SPE is a classic demonstrating the destructive psychological dynamics that arise when one group holds nearly total power and treats a devalued other group in a dehumanized environment. They stated that while intellectually serious alternative perspectives are welcome, they reject counterarguments that they view as ad hominem, misleading, inaccurate, and unscientific (PMID 32250143). Haslam's side replied that thanks to the archive, they were able to directly debate what happened in the SPE. They view the materials as showing that the experimenters used identity leadership to present guard brutality as necessary for a noble goal, and they encourage readers to examine the materials directly and test other interpretations (PMID 32250145). Another research team suggested that identity leadership may have also operated through an indirect pathway called 'integrative complexity', stating that this reinforces Haslam's thesis (PMID 32250144). Haslam's side summarizes that strict norms do not arise on their own, but were painstakingly crafted and activated by the experimenters (preprint, DOI: 10.31234/osf.io/ktsrq). It cannot be confirmed from the abstract alone how Zimbardo's side responded to individual facts such as the borrowing of student experiments or guard instructions. Meanwhile, Le Texier pointed out in a rejoinder titled 'The SPE remains refuted' that none of the responses from Zimbardo's side mentioned the student experiments the SPE relied upon. The author stated that this manuscript was rejected by the editor of American Psychologist on the grounds that it added nothing new to the discussion of the original papers and that the tone was not sufficiently collaborative, thus remaining as a preprint (preprint, DOI: 10.31234/osf.io/9a2er).

Meanwhile, the 'power of the situation' itself has not vanished. Even in a partial replication of Milgram that proceeded only up to the 150-volt mark where learners first protest in order to respect ethical standards, the replication authors report that the compliance rate estimated for beyond that point remained at a level slightly lower than the original results (PMID 19209958). However, there is also criticism that this replication is 'obedience light', having removed a substantial portion of the stress situation of the original experiment (PMID 19209962). This replication is a report that people significantly following demands is still observed today, and whether this influence is 'obedience' or 'identification' is the issue addressed in the previous section.

Regarding the simple narrative that 'the situation automatically makes people evil', post-archive research has raised doubts. Haslam's side interprets that what makes ordinary people brutal is not the given role itself, but rather identity leadership that frames that role as a noble cause and leads them to identify with it, along with followership that actively moves in line with it (PMID 31380665). In this interpretation, the guards in the SPE did not just fall into an empty role but were persuaded that abuse was 'necessary work', and Milgram's participants did not succumb to orders but joined in a cause. Zimbardo's side still maintains their original interpretation of the power of a dehumanized environment (PMID 32250143). In the BBC study, when the guards failed to identify with their role, they could not exercise authority and were overpowered by the prisoners. However, this study is a single experimental case study, and it is also a study whose scientific validity was questioned by Zimbardo (PMID 16573869).

The real lesson of the SPE may lie not inside the experiment, but in the history of the experiment itself. Criticisms existed long ago but did not reach textbooks, and with the release of the archive, new evidence and debates were added to those criticisms. How this debate will end is still open. Re-reading a myth that used to be summarized in a single sentence through evidence and counterarguments is closer to an honest story than the phrase 'situations make people evil'.

This article is solely for providing psychology and social science information, and does not replace definitive judgments on specific individuals or events.

Source Papers

Myth — Formation and Iconization of the SPE

• Zimbardo 40th-anniversary interview (PMID 22849005)
• Correction policy proposal 25 years after the SPE (PMID 9699456)
• SPE: Icon and Controversy (DOI: 10.1093/obo/9780199828340-0269)
• Encyclopedia of Corrections SPE entry (DOI: 10.1002/9781118845387.wbeoc176)
• Encyclopedia of Sociology Zimbardo experiment (DOI: 10.1002/9781405165518.wbeosz001)
• The Lucifer Effect (DOI: 10.1002/9780470672532.wbepp149)
• The nature-of-conformity debate (Milgram and Zimbardo) (PMID 23185132)
• Post-war psychologization: From Milgram to Zimbardo (PMID 21322973)

Omission of Criticism in Textbooks

• Content analysis of introductory psychology textbooks (DOI: 10.1177/1475725714568007)
• SPE analysis in introductory psychology textbooks (DOI: 10.1177/0098628314537968)
• SPE analysis in social psychology textbooks (DOI: 10.1177/0098628314549703)
• Survey of instructors on SPE lectures (DOI: 10.1177/0098628316636290)

Deconstruction — Demand Characteristics, Coaching, and Archives

• SPE debunking (archives and 15 interviews) (PMID 31380664)
• Demand characteristics of guard orientation (PMID 30961456)
• Identity leadership and SPE brutality (PMID 31380665)
• Staging coercion: Reading the SPE guards anew (DOI: 10.1177/2632666320944316)
• Participant self-selection and brutality (PMID 17440210)
• Teaching scientific thinking with archives (DOI: 10.53841/bpsptr.2019.25.2.39)
• The SPE remains debunked (rebuttal to Le Texier) (preprint, DOI: 10.31234/osf.io/9a2er)

Alternative Paradigm — The BBC Prison Study

• The BBC Prison Study: Rethinking the psychology of tyranny (PMID 16573869)
• When prisoners take over the prison: The social psychology of resistance (PMID 21885855)
• Identity entrepreneurship and leadership in the BBC study (DOI: 10.1177/019027250707000204)
• Zimbardo's critique of the BBC study (PMID 16573871)
• The tyranny of psychology debate: Reply (PMID 16573872)
• Escaping the theoretical prison (Turner) (PMID 16573870)
• Beyond the banality of evil: Interactionism (PMID 17440199)

Reinterpreting Milgram — Engaged Followership

• Working toward the experimenter (reconceptualizing followership) (PMID 26168469)
• "Glad to be of service": The Yale archives (PMID 25196821)
• Appealing not just to authority, but to science (DOI: 10.1111/josi.12072)
• Fifty years of obedience: From blind conformity to engaged followership (DOI: 10.1146/annurev-lawsocsci-110316-113710)
• Disproving the agentic state view through VR (PMID 30596731)
• Origins and early evolution of the Milgram experiment (PMID 21366616)
• Critique of engaged followership: Multiple conformity processes (PMID 29527775)
• The obedience alibi (DOI: 10.1515/auk-1998-0105)

The Honest Current Status

• Zimbardo and Haney response (2020 debate) (PMID 32250145)
• Reaffirming the power of de-individuating environments (PMID 32250143)
• Integrative complexity and identity leadership (PMID 32250144)
• Opening the prison doors: Debate on leadership, conformity, and dissent (preprint, DOI: 10.31234/osf.io/ktsrq)
• Partial replication of Milgram today (PMID 19209958)
• "Obedience lite" (PMID 19209962)