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The True Story Behind the Stanford Prison Experiment

The Stanford Prison Experiment showed how normal individuals can sink into depravity given the right circumstances
The Stanford Prison Experiment showed how normal individuals can sink into depravity given the right circumstances

The Stanford Prison Experiment commenced with a seemingly innocuous advertisement in the classified section: “Male college students required for a psychological exploration of prison life. Compensation of $15 per day for a duration of 1-2 weeks.” This proposition, set to unfold within a simulated prison environment established in Jordan Hall at Stanford University, garnered the interest of over 70 volunteers.

Spearheading this investigation was 38-year-old psychology professor Philip Zimbardo. Together with his team, they meticulously selected 24 participants, assigning them arbitrarily as either prisoners or guards.

Zimbardo imparted a sense of authenticity to the guards, urging them to internalize their roles as genuine custodians of a real penitentiary. He established a cardinal rule: physical harm towards prisoners was prohibited. However, he advised the guards to foster a climate of utter powerlessness among the inmates.

The study was initiated on Sunday, August 17, 1971. Yet, the full gravity and implications of what they embarked upon remained uncertain for all involved.

Four decades later, the Stanford Prison Experiment still stands as one of the most remarkable and infamous research endeavors ever undertaken at the university. This six-day ordeal subjected half of its participants to severe and degrading treatment from their fellow participants. The ‘prisoners’ experienced a range of abuses: they were subjected to mockery, forced nudity, sleep deprivation, and compelled to use plastic buckets as makeshift toilets.

Responses varied dramatically – some reacted with violent rebellion, others were overwhelmed by hysteria, and a few sank into deep despair. Amidst the escalating turmoil, the overseeing researchers remained passive observers. This continued until a moment of reckoning arrived, prompted by the intervention of a concerned colleague.

The SPE’s allure and its profound implications – particularly Zimbardo’s observation that “ordinary college students could do such terrible things when caught in that situation” – catapulted Zimbardo to global prominence. However, this fame was accompanied by scrutiny from peers who challenged the ethicality of exposing student volunteers to such severe emotional distress. Although the experiment received approval from Stanford’s Human Subjects Research Committee, Zimbardo admits that neither the committee nor the researchers foresaw the extreme cruelty exhibited by the guards.

Stanford prison

Researchers and guards felt it was important to sustain the illusion that it was an actual prison, not a room in the psychology building.

In 1973, the American Psychological Association conducted an inquiry, determining that the prison study had adhered to the ethical standards of the time. Nevertheless, this incident led to a significant revision of these guidelines, specifically forbidding human-subject simulations akin to the SPE. “No behavioral research that puts people in that kind of setting can ever be done again in America,” Zimbardo remarks.

The SPE has been the focus of numerous books, documentaries, a feature film, and even inspired the name of a punk band. In recent years, especially following the disclosure of mistreatment by U.S. military and intelligence personnel in prisons in Iraq and Afghanistan, the SPE has offered insights into how otherwise ethical individuals can behave heinously under adverse circumstances.

The behavior of the guards in the Stanford Prison Experiment has been a subject of intense ethical scrutiny, particularly due to its potentially harmful psychological effects on participants. This concern is often paralleled with the ethical debates surrounding the Milgram experiment at Yale University in 1961, which explored obedience to authority.

In the SPE, the measures employed by the guards to assert control and humiliate the prisoners were extreme. This included the systematic stripping and “delousing” of prisoners, along with dressing them in smocks without underwear, a tactic aimed at inducing humiliation and emasculation. The intended effect was to mirror the degradation experienced by real prisoners, and indeed, the treatment led to noticeable changes in the prisoners’ behaviors and self-perceptions.

One of the most serious ethical concerns was the continuation of the experiment even after participants expressed a desire to withdraw. Despite being informed of their right to leave at any time, in practice, this option was not readily facilitated by the researchers. This approach contradicted the agreements made with participants and the ethical standards of the time, although it’s important to note that ethical oversight in psychological research was less developed then compared to current standards.

In the aftermath of the SPE, and other similar studies, there has been a significant tightening of ethical guidelines for human subject research. Institutional Review Boards (IRBs) in the US and Ethics Committees in the UK now rigorously review human studies to ensure compliance with ethical guidelines established by bodies such as the American Psychological Association or the British Psychological Society. These guidelines emphasize the balance between potential scientific benefit and the risk of physical and psychological harm to participants.

A crucial component of these ethical guidelines is the immediate post-experimental debriefing. This process is vital for assessing and mitigating any psychological harm incurred during participation in an experiment. In the case of the SPE, while debriefing sessions were conducted, they took place years after the experiment, which is not in line with current standards that advocate for prompt debriefing. If immediate debriefing is not possible, researchers are obliged to take measures to minimize potential harm to participants. This shift towards more stringent ethical considerations in psychological research underscores the importance of prioritizing the well-being and informed consent of participants in any experimental setting.

The Origins of the Stanford Prison Experiment

The official website of the SPE succinctly outlines the objective of the experiment: to explore the psychological impacts of assuming the roles of either a prisoner or prison guard. This was to be observed in a controlled environment – a mock prison – where the behavior of all individuals within its confines would be meticulously recorded and analyzed.

A more elaborate exposition of the experiment’s purpose is found in a 1996 article from the Stanford News Service. Here, Zimbardo’s underlying motive is detailed as an investigation into the influence of roles, rules, symbols, group identity, and the situational validation of behaviors normally abhorrent to the average person. Zimbardo explained, particularly during a Toronto symposium in the summer of 1996, that his prior research had delved into how ordinary individuals could be swayed towards anti-social behaviors in scenarios where anonymity prevailed, or where others were dehumanized or seen as adversaries.


The prisoners lined up for the Stanford Prison Experiment

The experiment received funding from the US Office of Naval Research, with the specific aim of shedding light on anti-social behavior. This interest stemmed from a need within the United States Navy and the United States Marine Corps to better understand the dynamics of conflict between military guards and prisoners.

Despite its historical significance, the SPE has been the subject of ongoing criticism, particularly concerning its methodology. Critics have questioned whether it truly qualifies as a scientific experiment and have raised concerns about the potential for demand bias induced by the orientation given to the guards.

Preparation for the Experiment

Upon receiving authorization from the university, the organizers of the study sought participants through advertisements placed in the “help wanted” sections of the Palo Alto Times and The Stanford Daily newspapers in August 1971. The ad read:

“Male college students needed for psychological study of prison life. $15 per day for 1–2 weeks beginning Aug. 14. For further information and applications, come to Room 248, Jordan Hall, Stanford U.”

This solicitation drew responses from seventy-five men. Following thorough screening assessments and interviews, 24 were chosen to partake in a two-week prison simulation. These applicants were primarily white, middle-class, and exhibited signs of psychological stability and health. The selection process was designed to exclude individuals with criminal records, psychological disorders, or medical issues.

However, the methodology and participant selection of the study have been subjects of critique. Critics suggest that the advertisement’s emphasis on a need for prisoners and guards, rather than a social psychology study, might have introduced selection bias. Thomas Carnahan and Sam McFarland, in a 2008 analysis, posited that those who responded to the SPE advertisement might inherently possess traits linked to abusive behavior. They argued that traits like aggression, right-wing authoritarianism, Machiavellianism, social dominance orientation, and narcissism could be more pronounced in volunteers for a prison experiment. They also suggested that lower levels of dispositional empathy and altruism might characterize those who would volunteer.

The participants were randomly divided, with half assigned to the role of guard (nine, plus three alternates) and the other half as prisoners (also nine, plus three alternates). They consented to a commitment of 7 to 14 days, with compensation set at $15 per day, which is approximately equivalent to $108 in 2022.


Prisoner Stu Levin was among those whose breakdowns prompted an early shutdown of the study.

Prior to the commencement of the Stanford Prison Experiment, a makeshift prison environment was established. This was done by transforming a 35-foot section of the basement in Jordan Hall, Stanford’s psychology building, into a mock correctional facility. The setup included small cells, each designed to accommodate three prisoners. These cells, measuring 7 feet by 10 feet, were devoid of lighting and equipped with a cot for each inmate. Alongside this, the facility featured a corridor serving as the prison yard, a closet for solitary confinement, and a larger space allocated for the guards and warden.

The roles within the experiment were clearly defined. Philip Zimbardo himself assumed the role of the Superintendent, while undergraduate research assistant David Jaffe acted as the Warden. Notably, in 2017, digitized recordings from the experiment surfaced on the SPE’s official website, drawing significant attention. One particular recording highlighted Warden David Jaffe encouraging a guard to engage more actively and adopt a tougher stance for the sake of the experiment.

The guards underwent a specific orientation session the day before the experiment began. During this briefing, they were instructed to avoid physical harm or deprivation of food and drink to the prisoners, but to maintain order. To reinforce their authority, guards were equipped with wooden batons and outfitted in deindividuating uniforms akin to real prison guards, including khaki attire and mirrored sunglasses to prevent eye contact, thereby fostering a sense of anonymity.

The experiment’s protocol entailed addressing prisoners by numbers instead of their names, a strategy Zimbardo indicated was aimed at reducing their individuality. This lack of identity and control led to a sense of helplessness among the prisoners, causing many to become passive and resigned.

Zimbardo emphasized that the orientation for the guards in this simulation echoed the power dynamics typical of actual prison systems. While they were explicitly instructed to refrain from physical abuse, the overarching goal was to create an environment reminiscent of a real prison. The pressure applied on the guards to be assertive and involved in the SPE pales in comparison to the intense demands and potential consequences faced by guards in real-life prison and military settings, where non-compliance can lead to serious repercussions like disciplinary actions or job loss.

The Stanford Prison Experiment

Saturday, August 14 – Setup Day: The preparatory phase involved setting up the mock prison cells. Participants designated as guards attended an orientation session where they were briefed on their roles and received their uniforms.

Prisoners being handcuffed as part of the Stanford Prison Experiment

Prisoners being handcuffed as part of the Stanford Prison Experiment

Sunday, August 15 – Day 1: Arrest of Prisoners Participants assigned as prisoners experienced unexpected mock arrests by the Palo Alto police at their homes or designated locations. Although part of the experimental design, this element of surprise breached the ethical standards outlined in the contracts signed by participants. The arrest process included charges of armed robbery and burglary, complete with Miranda rights warnings, fingerprinting, and mug shots.  A local TV station reporter documented these procedures. Simultaneously, three guards prepared for the arrival of the inmates at the mock prison. Upon arrival, prisoners underwent a strip search, were assigned identification numbers, and received their prison uniforms.

Monday, August 16 – Day 2: Rebellion and Response Guards enforced identification by numbers and confined prisoners to their cells. Early in the morning, prisoners rebelled, refusing to comply with the guards’ directives. In response, the guards escalated their tactics, employing fire extinguishers to reassert control and imposing harsher punishments, including solitary confinement.

Tuesday, August 17 – Day 3: Escalation of Control: To suppress further rebellion, guards separated and rewarded compliant prisoners, while subjecting others to humiliation and deprivation, including restricted bathroom access and the use of buckets for relief. Douglas Korpi – Prisoner 8612: Douglas Korpi, known as Prisoner 8612, was the first to exit the experiment after exhibiting signs of extreme distress. However, in a 2017 interview, Korpi claimed his breakdown was feigned to facilitate his exit from the experiment, contradicting his earlier statements in the 1992 documentary “Quiet Rage,” where he acknowledged the profound impact of the experiment on his life. Zimbardo, responding to this assertion, insisted on treating the breakdown as genuine during the experiment and expressed skepticism about Korpi’s later claim.

Wednesday, August 18 – Day 4: Division and Distress: As the guards continued to differentiate between compliant and rebellious prisoners, fractures emerged among the inmates. Those who had rioted suspected others of being informants, while some prisoners viewed the rebels as jeopardizing their chances of regaining basic comforts like sleeping cots and clothing. “Prisoner 819” exhibited severe emotional distress, manifesting in tears and a refusal to speak with a visiting priest. Instead, he requested a medical doctor. Recognizing his acute distress, Zimbardo intervened, affirming his true identity and facilitating his removal from the experiment. As he departed, guards instigated the remaining prisoners to chant a derogatory slogan about “819.”

Thursday, August 19 – Day 5: Visitation and Ethical Confrontation: The fifth day was designated for family and friends to visit, mimicking a real prison environment. Zimbardo and the guards implemented strict visitation rules, including prolonged waiting times and brief, supervised interactions, which raised concerns among visitors about the welfare of the inmates. This led to some parents considering legal action for the early release of their sons.

On the same day, Zimbardo’s colleague, Gordon H. Bower, visited the experiment, raising questions about its scientific validity, specifically regarding the independent variable. That night, Christina Maslach, another colleague, was visibly disturbed upon witnessing the abusive treatment of prisoners by guards, including the use of bags over their heads. She confronted Zimbardo about his ethical oversight and the immorality of the study.

Her criticism, particularly noting a disturbing change in Zimbardo’s demeanor due to his role as the Superintendent, was pivotal in his decision to terminate the SPE the following day. Her intervention highlighted significant ethical concerns and the profound impact the experiment was having on all participants, including Zimbardo himself.

Dave Eshelman the most sadistic guard-morbidkuriosity

Dave Eshelman the most sadistic guard

Friday, August 20 – Day 6: Conclusion and Debriefing: On the sixth day, influenced by Christina Maslach’s objections, the concerns raised by parents, and the escalating severity of the guards’ behavior, Philip Zimbardo made the decision to terminate the Stanford Prison Experiment. He convened a meeting with all participants, including the guards, prisoners, and research team members such as David Jaffe and Craig Haney, to announce the experiment’s conclusion. Participants were informed they would be compensated for the six days of participation.

Zimbardo conducted extensive debriefing sessions, beginning separately with the prisoners and guards, and then bringing everyone together for a collective discussion. These sessions aimed to help participants process their experiences and understand the study’s dynamics. Additionally, each participant was requested to write and submit a personal reflection on their experience in the coming days. A follow-up meeting was scheduled for a week later to discuss the experiment’s impact further and gather feedback.

Subsequently, the physical setup of the “Stanford County Jail” was dismantled, and the basement area of Jordan Hall was restored to its original function as offices for graduate students. Zimbardo, together with his graduate student researchers Craig Haney and Curtis Banks, began the rigorous process of analyzing the extensive data collected from the experiment.

This analysis laid the foundation for several scholarly articles and for Zimbardo’s in-depth exploration of the SPE in his later work, “The Lucifer Effect,” published in 2007. This book delves into the psychological mechanisms that can lead ordinary people to engage in acts of evil, using the SPE as a central case study.

The Aftermath of the Stanford Prison Experiment

The Stanford Prison Experiment (SPE) has faced significant criticism over the years for its methodology and ethical considerations, particularly regarding the concept of ‘demand characteristics’ – the idea that participants in psychological experiments tend to behave in ways they believe the experimenters expect or want.

In 2012, psychologist Peter Gray critiqued the SPE for exhibiting demand characteristics, arguing that the participants might have been acting out based on their stereotypical perceptions of how prisoners and guards behave, rather than responding to the prison environment itself.

This argument was echoed earlier, in 1975, by Ali Banuazizi and Siamak Movahedi, who suggested that the participants’ behavior in the SPE was a product of these demand characteristics rather than the simulated prison setting. They contended that there’s no single, universally accepted way of behaving as a prisoner or guard, and thus the participants were likely just playing the roles they were cast in.

In 2013, Peter Gray further emphasized the influence of demand characteristics on the SPE. He noted that the behaviors exhibited by the guards were implicitly endorsed by the absence of intervention from Zimbardo and his assistants. Gray challenged the notion that Zimbardo conducted the experiment to understand situational influence on behavior, instead proposing that Zimbardo aimed to prove pre-existing notions about the abusive nature of guards and the submissiveness of prisoners.

Thibault Le Texier, a French researcher, also criticized the experiment in his 2018 book “Histoire d’un Mensonge” (‘The History of a Lie’), and in a subsequent 2019 article published by the American Psychological Association. He used testimonies from guard participants to argue that the observed sadistic behaviors and submission were a direct result of Zimbardo’s instructions and the guards’ eagerness to please the researchers.

Prisoners were forced to wear gowns — “dresses” — to emasculate and humiliate them.

Prisoners were forced to wear gowns — “dresses” — to emasculate and humiliate them.

Dutch historian Rutger Bregman, in his 2020 book “Humankind: A Hopeful History”, labeled the experiment as dubious, stating that guards were encouraged to act aggressively. He suggested that such experiments are often designed to create hostility and then interpreted in a way that suits the researchers’ objectives.

David Eshelman, one of the guards in the SPE, admitted that his theater background influenced his actions, and he actively thought of new ways to demean the prisoners. In response to the suggestion that Eshelman’s behavior was influenced by external sources like movies, Zimbardo countered by pointing out that other guards exhibited similar behaviors without such influences. He also drew parallels between the actions of the guards in the SPE and real-world prison abuses, like those at Abu Ghraib, arguing that the behaviors weren’t mere acting but reflective of real tendencies.

The ongoing debate about the SPE reflects the complexities and ethical dilemmas inherent in psychological research, particularly in studies involving role-playing and simulated environments.

Philip Zimbardo’s interpretation of the Stanford Prison Experiment posits that the behaviors exhibited by participants were primarily a result of the simulated prison environment, rather than their individual personality traits. This perspective aligns with the concept of situational attribution, which is also evident in the findings of the Milgram experiment, where individuals complied with instructions to administer what they believed were harmful electric shocks to others.

However, some analysts argue that the behavior of the guards in the SPE was influenced more by encouragement from the researchers than by the situation itself.

The conclusions and observations drawn from the SPE have been criticized for their subjective and anecdotal nature, making the experiment difficult for other researchers to replicate accurately. In 1973, social psychologist Erich Fromm contested the study’s findings, noting that only a fraction of the guards exhibited sadistic tendencies. He argued that this fact undermines the idea that the situation alone dictated behavior, suggesting instead that individual personality traits play a significant role. Fromm also criticized the methods used to screen participants, questioning their effectiveness in assessing latent sadistic tendencies.

Zimbardo met with parents of the prisoners to address concerns about conditions and the prisoners’ mental states.

Zimbardo met with parents of the prisoners to address concerns about conditions and the prisoners’ mental states.

Moreover, the SPE has been referenced in discussions of cognitive dissonance theory and the influence of authority. It raises questions about how awareness of being observed (the Hawthorne effect) might shape behavior. Critics noted that the guards might have been emboldened to act more aggressively because supervisors, who were observing the experiment, did not intervene.

Critics have consistently challenged the validity and merit of the SPE’s findings, arguing that factors like demand characteristics (participants acting in ways they think researchers expect) and selection bias significantly impacted the results. This ongoing debate highlights the complexities in interpreting psychological experiments and underscores the importance of considering both situational and individual factors in understanding human behavior.

Next, read about the Dungarvon Whooper of New Brunswick, and then, about the Texas Tower Shooter!

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Written By

Abin Tom Sebastian, also known as Mr. Morbid in the community, is an avid fan of the paranormal and the dark history of the world. He believes that sharing these stories and histories are essential for the future generations. For god forbid, we have seen that those who forget history are doomed to repeat it.

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