Re-assessing the “Lucifer Effect”: A Critical Review of the Stanford Prison Experiment’s Theory, Methods, and Ethics

¹Independent Scholar, Lahore, Pakistan

^{2Department of Family Practice, The University of British Columbia, Vancouver, BC, Canada}

^*Corresponding Author: Prof. Iqbal Akhtar Khan, MBBS DTM FACTM PhD, Independent Scholar, Lahore, Pakistan, Email: [email protected]

Received Date: June 13, 2026

Published Date: August 28, 2026

Citation: Khan IA, Khan M.. (2026). Re-assessing the “Lucifer Effect”: A Critical Review of the Stanford Prison Experiment’s Theory, Methods, and Ethics. Mathews J Psychiatry Ment Health. 11(2):67.

Copyrights: Khan IA and Khan M. © (2026).

ABSTRACT

The Stanford Prison Experiment (SPE), conducted in 1971 by Prof. Philip Zimbardo and colleagues at Stanford University, is widely recognized as one of the most influential studies in social psychology. The experiment purportedly demonstrated that situational forces can rapidly transform ordinary individuals into perpetrators of abusive behavior within institutional contexts. Zimbardo later developed the theoretical concept known as the “Lucifer Effect,” which proposes that systemic and situational pressures can lead ordinary individuals to commit immoral acts.

 Despite its prominence in psychological literature and education, the validity and interpretation of the SPE have been increasingly questioned. This review critically re-evaluate the methodological flaws and ethical shortcomings associated with SPE. The findings highlight major methodological concerns such as demand characteristics, lack of experimental control, researcher influence, participant role-playing, and potential selection bias. Significant ethical issues, including psychological harm, inadequate informed consent, evil of inaction syndrome and researcher bias were also identified.

Whereas the SPE is now famously cited as a "cautionary tale" highlighting the necessity of rigid ethical protocols for human subjects, it has played a pivotal role in shaping modern ethical standards through the introduction of Public Health Law 93-348 on July 12,1974 and the key changes made through the evolution of APA Ethics Code.

Keywords: Stanford Prison Experiment, Lucifer Effect, Social Psychology, Research Ethics, Institutional Power, Inaction Syndrome, Researcher Bias

INTRODUCTION

“The Lucifer Effect raises a fundamental question about the nature of human nature: How is it possible for ordinary, average, even good people to become perpetrators of evil?”- Philip Zimbardo [1].

The Lucifer Effect, the term coined by American social psychologist Prof. Philip George Zimbardo (1933-2024), describes how ordinary, good people can commit evil acts when placed in powerful situational or systemic contexts, transforming from moral individuals to perpetrators of cruelty. This was best known from the Stanford Prison Experiment (SPE), where participants assigned to be guards or prisoners quickly adopted their roles, with guards becoming sadistic and prisoner’s passive.

Lucifer, meaning "light-bringer" or "morning star, “in Latin, as seen in Holy Bible [Link: Isaiah 14:12], ("How art thou fallen from heaven, O Lucifer, son of the morning!...") is primary antagonist to God and humanity, standing for pride, rebellion, and sin. The name Lucifer became synonymous with Satan (meaning "adversary") after interpretations linked biblical passages about fallen kings (like in Isaiah 14) to Satan's rebellion, as seen in John Milton's "Paradise Lost". The historical figure of Lucifer holds no literal presence in the SPE; rather, Zimbardo used the name metaphorically in his Best-Selling Book of 2007.

The SPE was a highly controversial and massively influential study. A size-able and critical literature of the study has appeared, leading to its status as ‘‘one of the most researched, discussed, and analyzed studies in the history of psychology’’ [2]. However, with passage of time and availability of added information it became widely considered a flawed scientific presentation that, according to some of modern critiques, functioned more like “a staged drama” or “a demonstration” rather than a rigorous experiment.

This review critically reassesses the Lucifer Effect by revisiting the SPE’s historical foundations, evaluating its methodological flaws and ethical shortcomings, and considering alternative explanations for the observed behaviors. Rather than trying to dismiss the experiment outright, the article looks to contextualize its findings and extract responsible lessons for modern psychological studies (Figure 1).

Figure 1: Conceptual illustration of the Lucifer Effect as an interaction between situational pressure, institutional power, researcher influence, and individual moral agency (AI. Generated)

Objectives

1. Reassess the theoretical foundation of the Lucifer Effect as derived from the SPE.
2. Critically evaluate the methodological flaws and ethical shortcomings of the SPE.
3. Identify lessons relevant to contemporary research ethics, institutional design, and social responsibility.

Historic Perspectives

Rationale of SPE

"Research is to see what everybody else has seen, and to think w.hat nobody else has thought."- Albert Szent-Gyorgyi (1893-1986) - Hungarian Biochemist (Nobel Laureate 1937).

The SPE is one of the most famous experiments in the history of psychology [3]. Much has been said about its background but the most interesting and certainly authentic is what the Originator and Executor of the Experiment - the Principal Investigator has narrated.

Prof. Zimbardo, in his Best-Selling Book of 2007, recollects his intent to lay out for the interviewers some of the procedural details of the study as well as some of the reasons for doing this kind of experiment.

One of them asked: “My question is this, Doc: What's the point of going through all the trouble to set up a prison of your own down at Stanford, arresting these college students, paying out all that money, when we already have prisons enough and criminals enough? Why not just observe what goes on in the county jail or the action over at San Quentin? Wouldn't that tell you what you want to know about guards and prisoners in real prisons”? [1].

Returning to his professorial role, eager to profess to curious listeners, Zimbardo replied : "I am interested in discovering what it means psychologically to be a prisoner or a prison guard. What changes does a person undergo in adapting to that new role? Is it possible in the abbreviated time of only a few weeks to take on a new identity that is different from one's usual self”? [1].

This is the explanation, by the Principal Investigator of the famous SPE, of his groundbreaking piece of research, later published as “The Lucifer Effect: Understanding How Good People Turn Evil”. It would be in the fitness of the things, before we could concentrate on SPE, to refer to Milgram’s Obedience Experiment and Arendt’s Concept of the “Banality of Evil” which had significant impact on SPE.

Milgram’s Obedience Experiment

The Milgram Obedience Experiment, conducted by American social psychologist Stanley Milgram (1933-1984), at Yale University’s Interaction Laboratory, from July 1961 to May 1962 describes a procedure for the study of destructive obedience in the laboratory. The participants were instructed by an authority figure to administer increasingly intense electric shocks (for giving wrong answers) to a “learner” (an actor), who feigned pain and distress. Despite hearing the actor’s screams, most participants continued administering shocks, showing the powerful influence of authority figures on behavior [4]. There are some situational factors that can explain such elevated levels of obedience:

         i.    The physical presence of an authority figure dramatically increased compliance changing behavior even when it goes against their values. The authority figures (especially when physically present at the venue) exert a noteworthy influence on behavior. The term “Hawthorne Effect” (coined by researcher Henry Landsberger in 1958) describes how people tend to change their behavior when they are aware of being observed, rather than due to changes in environmental conditions [5].

ii.   The fact that Yale (a trusted and authoritative academic institution) sponsored the study led many participants to believe that the experiment must be safe. The key takeaways showed that the people often obey authority figures, even when it goes against their values and situational power can override personal morality, with implications.

Zimbardo was a former classmate of Milgram and was interested in further investigating the impact of situational variables on human behavior. However, there was a crucial difference Whereas Milgram’s research focused on individual compliance in the face of an authority figure’s increasingly and unjust demands, the SPE examined the conformity pressures brought to bear on groups of people functioning within the same institutional setting [6].

Table 1. Milgram Experiment vs. Stanford Experiment

Arendt’s Concept of the “Banality of Evil”

“Can one do evil without being evil”? was the puzzling question which Hannah Arendt (1906–1975), a German-born American political theorist and philosopher, grappled with. It stemmed from her coverage of the 1961 Jerusalem trial of Adolf Eichmann, a key organizer of the Holocaust [7]. To answer, she presented the concept "Banality of Evil” in her 1963 book, “Eichmann in Jerusalem: A Report on the Banality of Evil”. The concept is a notion of evil that has no roots in “evil motives”. It describes how horrific acts could be performed by people inconsiderate for others. The evil arises from inability to think critically by the people who are often not inherently evil but become “cogs “(a subordinate but integral part or person) in a large, destructive machinery. Arendt argues that the concept does not minimize the horror of the acts but rather explains the terrifying normality of the people committing them and the systems that facilitate [8].

Setting the Stage for SPE

“My most notable study was the 1971 Stanford Prison Experiment, which was a classic demonstration of the power of social situations to distort personal identities and long cherished values and morality as students internalized situated identities in their roles as prisoners and guards.” - Philip Zimbardo [1]

The SPE, funded by the U.S. Office of Naval Research and the U.S. Marine Corps, was designed by Prof. Philip Zimbardo to investigate the psychological effects of perceived power, authority, and situational factors on human behavior. Approval for the study was given from the U.S. Office of Naval Research, Stanford University’s Psychology Department and the University Committee of Human Experimentation. The purpose of the study was:

-       To investigate how rapidly people adopt roles in a prison like environment.

-       To examine the impact of situational forces vs personal dispositions on behavior.

-       To study the psychological effects of perceived power.

The entire exercise started with press advertisement placed in the “Help Wanted” sections of the “Palo Alto Times” and “The Stanford Daily” in August 1971. To carry out the experiment, the Principal Investigator set up a mock prison in the basement of Stanford University's psychology building and selected 24 male undergraduate students to play the roles of both prisoners and guards. The selectees were from a larger group of 70+ volunteers, based on having no criminal background, no psychological issues, no significant medical conditions. The experimenters judged them to be the "most stable (physically and mentally), most mature, and least involved in antisocial behaviors” [9].

Whereas this small unrepresentative homogenous group may be a convenience sample, in view of the limited occupancy of the simulated prison, it limits the generalizability of the findings to diverse populations. Some critics have alleged that the randomization procedures were inadequately documented. However, the Principal Investigator, when questioned, made it clear by saying: “we randomly assigned all the volunteers to each of the two conditions, like tossing a coin. If it came up heads, the volunteer was assigned to be a guard; if it was tails, a prisoner” [1].

As a matter of principle, the true informed consent requires participants to be fully aware of all potential risks, which was not done in SPE. Whereas the participants agreed to a “psychological study of prison life,” they did not expect the extreme psychological distress, humiliation, and dehumanization they would endure. All this was unpredictable as the SPE proposal had been reviewed and given prior approval by the Human Subjects Committee, and by other institutional units at the University and in 1971, none of them had seen any problem with a simulation, role-playing study. [10]. Another issue was deprivation of the “Right to Withdraw”. While the participants technically had the right to withdraw, the environment made it impossible for them to exercise this right.

The Role Induction Process of SPE

Given that the success of the SPE was relying on participants’ hurried and complete immersion into their assigned identities, the researchers implemented specific procedures to ease this role induction, both for the guards and the prisoners.

Saturday’s Guard Orientation

On Saturday (a day before the formal start of the experiment) the researchers had an “Orientation Meeting” with the designated guards to give them their assignments. The Principal Investigator Prof. Zimbardo narrates the minutes himself:

“We cannot physically abuse or torture them (the prisoners). We can create boredom. We can create a sense of frustration. We can create fear in them, to some degree. We can create a notion of the arbitrariness that governs their lives, which are totally controlled by us, by the system, by you, me, Jaffe. They will have no privacy at all; there will be constant surveillance, nothing they do will go unobserved. They will have no freedom of action. They will be able to do nothing and say nothing that we do not permit. We are going to take away their individuality in various ways. In general, what all this should create in them is a sense of powerlessness. We have total power in the situation. They have none. We would have to make them feel as though they were in prison; we should never mention this as a study or an experiment” [1—page 55].

He adds that his orientation speech was designed to get the guards "into the mood of the joint" by outlining some of the key situational and psychological processes at work in typical prisons [1–page 55]. After this forceful orientation, the guards became highly compliant to Zimbardo and his team. Zimbardo himself appreciates: “the behavior of the guards was as interesting as, or sometimes even more interesting than, that of the prisoners” [1].

Sunday’s Media Spectacle Arrests of Would-be Mock Prisoners

The Principal Investigator suggested to the Chief of Palo Alto Police (with whom he was constantly in contact) that the ideal way to start the study, most realistically and with dramatic flair, was to stage arrests of the would-be mock prisoners as “dangerous suspects”. The charge was burglary for the first five suspects, a 459 Penal Code violation, and armed robbery for the next four arrests, a Section 211 Code [1]. So, the boys were arrested on Sunday morning August 14,1971 from their residences using standard operating procedure, in presence of the Media. They were subjected to handcuffing on being taken into custody, transporting them in police cars and taken to police headquarter, and upon arrival there finger printing, mug shot, stripping naked, strict search, subjecting to a delousing spray and blind folding, before being taken to the simulated prison.

Putting on Uniform for the Guards and the Prisoners

The quote “the mere fact of putting on uniforms was sufficient to transform [participants] into passive prisoners and aggressive guards.” [11] is attributed to Prof. Zimbardo. He argued that this transformation proved that social roles, rather than personality, can cause normal individuals to engage in immoral actions.

The uniforms were intended to reduce individuality (deindividuation) and enhance the power of the situation. The uniform for the guards consisted of a plain khaki shirt and trousers, a whistle, a police night stick (a wooden baton) and reflecting sunglasses to make eye contact impossible. Their uniforms were intended to convey a military attitude while the baton and whistle were symbols of control and power. With this they were ready to manage the mock prisoners. On reaching the simulated prison, the prisoners were forced to wear identical uniforms consisting of a smock (dress) without underclothes with prison ID number in front and back, a nylon stocking cap to cover their hair, and a chain bolted around their right ankle. The purpose of these uniforms was to quickly strip participants of their individuality, encourage submissive behavior, and create an intense sense of humiliation and impersonality.

Introduction of the Situational Rules

The situational rules came into effect the next day of induction of the prisoners. They were designed to legalize the power assigned to the guards so that they could justify most of the harm, they did to the prisoners, by referencing to "the Rules." Zimbardo himself realized the agony the prisoners had to endure to memorize the set of seventeen arbitrary rules that the guards and the warden David Jaffe (one of Zimbardo’s student research associates) had invented [1].

Following is the complete list:

• Prisoners must remain silent during rest periods, after lights out, during meals, and whenever they are outside the prison yard.
• Prisoners must eat at mealtimes and only at mealtimes.
• Prisoners must participate in all prison activities.
• Prisoners must keep their cell clean at all times. Beds must be made and personal effects must be neat and orderly. Floors must be spotless.
• Prisoners must not move, tamper with, deface, or damage walls, ceilings, windows, doors, or any prison property.
• Prisoners must never operate cell lighting.
• Prisoners must address each other by number only.
• Prisoners must always address the guards as "Mr. Correctional Officer" and the Warden as "Mr. Chief Correctional Officer."
• Prisoners must never refer to their condition as an "experiment" or "simulation." They are imprisoned until paroled.
• Prisoners will be allowed 5 minutes in the lavatory. No prisoner will be allowed to return to the lavatory within 1 hour after a scheduled lavatory period. Lavatory visitations are controlled by the guards.
• Smoking is a privilege. Smoking will be allowed after meals or at the discretion of the guard. Prisoners must never smoke in the cells. Abuse of the smoking privilege will result in permanent revocation of the smoking privilege.
• Mail is a privilege. All mail flowing in and out of the prison will be inspected and censored.
• Visitors are a privilege. Prisoners who are allowed a visitor must meet him or her at the door to the yard. The visit will be supervised by a guard, and the guard may terminate the visit at his discretion.
• All prisoners in each cell will stand whenever the warden, the prison superintendent, or any other visitors arrive on the premises. Prisoners will wait on orders to be seated or to resume activities.
• Prisoners must obey all orders issued by guards at all times. A guard's order supersedes any written order. A warden's order supersedes both the guard's orders and the written rules. Orders of the superintendent of the prison are supreme.
• Prisoners must report all rule violations to the guards.
• Failure to obey any of the above rules may result in punishment.

Follow ups of the Orientation Session

The creation of an atmosphere of powerlessness for the prisoners inadvertently contributed to the humiliating behaviors of the guards towards them. The guards, soon after being given the uniform and the status of “Mr. Correctional Officer”, started to abuse their “newfound power” by behaving sadistically demeaning, degrading, and hurting the "prisoners" day in and night out, displaying intense, inventive, or sadistic cruelty. Many of the cruel methods used (using bags over heads, forced nudity, sleep deprivation, and extreme harassment) were suggested or encouraged by the researchers to ensure the simulation felt "real."

Of note, detailed instructions to the guards were not limited to orientation sessions but continued to the end of the study as has been detailed in the forthcoming sub-heading “Demystifying Tyranny of the Guards”.

Rapid Deterioration of the Participants

The astonishing speed with which the participants assimilated into their roles was one of the most striking features of SPE. The guards quickly adopted their positions of authority, with their behavior escalating dramatically, moving beyond simple maintenance of order to active forms of psychological abuse and dehumanization. Zimbardo admits that the prisoners, being particularly upset by the constant abuse rained on them day and night, became submissive and emotionally distressed [1].

Tony Bradley, while summarizing the outcome of the SPE, inferred that the goal was to observe how people adapt to roles of authority and subordination. What followed was a gradual but shocking transformation. Within just 48 hours, guards began exhibiting authoritarian behavior, enforcing strict rules, and humiliating prisoners. Prisoners, in turn, became passive, anxious, and, in some cases, emotionally broken [12].

Abrupt End of the SPE

“At the start of this experiment, there were no differences between the two groups (guards and prisoners); less than a week later, there were no similarities between them”. - Philip Zimbardo [1].

At the peak of tense and volatile atmosphere in the prison, an outside psychologist, Christina Maslach was requested to interview guards and prisoners. She saw abusive, sadistic behavior by student guards against student prisoners, including a dehumanizing, chained toilet run with bags over their heads. Horrified by the brutal conditions and unethical treatment, she confronted Philip Zimbardo with direct, emotional objections. Her specific remarks and actions about the situation included:

·         "It's terrible what you are doing to these boys!"

·         "How can you see what I saw and not care about their suffering?"

Questioning the morality of the study, she argued that the experiment had become a "jails or hospitals" situation of "bullying or abuse," rather than a controlled psychological study. She challenged Zimbardo’s role for losing his objectivity as a researcher and becoming consumed by his role as "Superintendent of the Prison” (which he was) demanding that the study be shut down due to its inhumane conditions.

She was the only one, out of dozens of visitors, to object to the unethical, abusive, and dehumanizing treatment meted out to the prisoners. In her personal reflection published in 2025, she says “I revisit my experience as an unintentional ‘outsider ombudsperson,’ exploring the psychological and ethical challenges that unfolded within the SPE” [10]. At her insistence Zimbardo agreed to realize gravity of the situation. And the experiment, originally scheduled to last for two weeks, had to be aborted after only six days due to the intense psychological impact on the participants and often pathological reactions from many of them.

Outcomes of the SPE

“The SPE should not be used as a tool for understanding the prison system, but rather as an example of how lack of oversight compromises scientific findings” -Leo Novack [13].

The SPE quickly became a landmark study in social psychology, known for its shocking and unexpected outcomes. However, with passage of time, later investigations, and availability of uncovered audio recordings there is growing impression that the "experiment" was heavily influenced by the participants acting out roles prompted by the researchers. Consequently, according to some of modern critiques, it functioned more like a staged demonstration or dramatic performance designed to produce a predetermined outcome. Recent investigations, particularly by French researcher Thibault Le Texier, have uncovered that the study lacked basic scientific controls, included direct coaching of participants to act aggressively, and was often "theatrical" rather than observational [14]. Critics, including Le Texier and psychologists Reicher and Haslam, have described the SPE as a, "morality play disguised as science".

In 1998, Haney and Zimbardo wrote: “The outcome of our study was shocking and unexpected to us, our professional colleagues, and the general public” [15]. The balanced and learned opinion is of Richard Griggs professor emeritus at the University of Florida, "the SPE and its criticisms comprise a solid thread to weave numerous research concepts together into a good 'story' that would not only enhance student learning but also lead students to engage in critical thinking about the research process and all of the possible pitfalls along the way“ [ 16].

The ethical issues, perceived methodological shortcomings and inaccuracies in conduct of study have faced severe criticism. All these concerns would be discussed in detail in subsequent paragraphs

Table 2. Key Methodological and Ethical Criticisms of the SPE

Methodological Flaws of SPE

The SPE has faced intense ethical criticism for inability to adequately protect participants from harm and for the inadequacies of the informed consent process. A sizable part of the criticism centers on its methodological flaws. The key issues include sampling design, lack of control group, standardized behavioral measurements and systematic data collection procedures. Ribkoff argues that the SPE, a pseudo-scientific experiment, was a “surreal,” absurdist drama without a script because Zimbardo placed the student volunteers of the SPE in an improvisational, Kafkaesque performance “situation” without sufficient controls and without sufficient self- understanding. [17].

Shortcomings in Smooth Conduct of SPE

The booking process of would -be mock prisoners was fundamentally flawed, functioning less as a neutral scientific procedure and more as an engineered psychological, and physical, assault. The use of real Palo Alto police officers to arrest them at their homes (with charges of burglary and armed robbery) gave the event an undeserved air of legitimate authority. Zimbardo, when asked "Whether the prisoners knew they would be arrested as part of the experiment?”, answered in the negative. However, later he admitted that the booking process was deception of the participants [ 1].

In the conduct of SPE, guards played a critical role by adopting authoritarian roles, engaging in psychological abuse, and enforcing degrading conditions on "prisoners". Although forbidden from using physical violence, the guards created an atmosphere of fear and helplessness. Bartels argues that there are reasons to theorize that the Orientation Session sanctioned abuse among guards [ 18].

Ethical Concerns

The first criticism on the study is its being unethical and modern critiques argue that the SPE is more of a "case of ethical malfeasance" and a "social psychology myth" than a piece of scientific research. Whereas the SPE lacked sufficient independent ethical oversight during its execution, it knowingly placed prisoners in a situation designed to evoke extreme and potentially damaging acute stress reactions, severe anxiety, depression, and signs of breakdown. There is heated debate about it. Why not to invite Prof. Zimbardo, the Originator and Executor of the study, to plead his own case? Interestingly, he has well played on both the angles, leaving the ball in the court of the critics [1]. For the sake of brevity, the ethics can be categorized as "absolute" or "relative."

Table 3. Absolute vs. Relative Ethics of the SPE

Absolute Ethics / The SPE was Absolutely Unethical

According to Prof. Philip Zimbardo [1], following are the features of SPE that would qualify it as unethical:

1.        Whereas the absolute ethical standard postulates that because human life is sacred it must not in any way be demeaned, even unintentionally, there was no justification for any experiment that induces human suffering.

2.        Since there is no justification, in psychology or medicine, to conduct any study that violates the biological or psychological integrity of any human being regardless of the benefit that might, or even definitely accrue to the society at large, the SPE definitely caused mental anguish and physical agony to the prisoners. They suffered much more than they could have predicted when they volunteered for an academic study of "prison life" that was being conducted at a prestigious university.

3.        An important feature was not to disclose in advance the nature of the arrests and formal booking, on Sunday August1971, by Palo Alto police of the mock prisoners.

4.        The research team did not extend the mandate to restrict psychological abuse.

5.        The research team was also guilty of manipulating parents into thinking the situation of their sons not as bad as it was by the various deceptive and control procedures like putting out a good-looking red carpet, system managers counter complaints and concerns about the negative aspects of their situation, on Visiting Nights.

6.        Failure to terminate the experiment after the first prisoner suffered a severe stress disorder on Day 3 and not wait for the second prisoner to suffer from extreme disorders.

Relative Ethics/The SPE was Absolutely Ethical

Prof. Zimbardo argues “On the relativist side of the ethical argument, one could contend that the SPE was not unethical because of the following”:

1.        Approval for the study was given from the U.S. Office of Naval Research, Stanford University’s Psychology Department, and the University Committee of Human Experimentation and a homogeneous, "normal" sample was chosen after extensive interviewing and diagnostic testing of a large group of volunteer male college students. [9]

2.        The legal counsel of Stanford University consulted and drew up a formal "informed consent" statement which, signed by every participant, specified that during the experiment there would be a loss of privacy. All were expected to complete their two-week contract, and earlier release was possible for health reasons only.

3.        The Student Health Department was alerted to the study, and prior arrangements were made for any medical care subjects might need. Approval was officially sought and received in writing from the agency sponsoring the research, the Group Effectiveness Branch of the Office of Naval Research (ONR), the Stanford Psychology Department, and Stanford's Institutional Review Board (IRB).

4.        Aside from having the subjects arrested by the Palo Alto Police, there was no deception of the participants.

5.        Regarding his failure to terminate the experiment after the first prisoner suffered a severe stress disorder on Day 3 and not waiting for the second prisoner to suffer from extreme disorders, Prof. Zimbardo argued that he was planning to terminate the experiment on Sunday, at the end of a full week, as a "natural ending," had not Christina Maslach's intervention forced premature closure.

6.        He believed that the main reason he did not end the study sooner, when it began to get out of hand, resulted from the conflict created in him by his dual roles as principal investigator, and thus guardian of the research ethics of the experiment, and as prison superintendent, eager to maintain the integrity and stability of the prison at all costs [1].

7.        There is no question that people suffered during this experiment. Those who made them suffer also had to deal with the recognition that they had gone beyond the demands of their role to inflict pain and humiliation on others for hours on end. Therefore, the ethics in this and similar research demand careful consideration [1].

8.        It was Prof. Zimbardo who requested a post- experiment ethics evaluation by the American Psychological Association in July 1973, which found that the existing ethical guidelines had been followed [ 1].

Related Issues

These issues need to be discussed under following sub-headings:

—       Demystifying tyranny of the guards

—       Dehumanization of the Prisoners

—       Anonymity Shielding and Deindividuation

—       The Evil of Inaction Syndrome: Passive Bystanders

—       Researcher Bias: Dual Role of Zimbardo

The study was terminated prematurely because it was getting out of control in the extent of degrading actions being perpetrated by the guards against the prisoners - all of whom had been declared normal, healthy, ordinary young college students, less than a week before.

Demystifying Tyranny of the Guards

 “What was the assigned role of the guards in SPE? Were they given their Job Description?” The answer to this important question is, unfortunately, not straight forward, rather confusing and, at occasions, full of contradictions. The Investigators claimed that:

         i.            What the guards did, they did “without training from the Investigators in how to be Guards” [19].

        ii.            The guards made their own decisions about how to run the prison and that their aggression was “emitted simply as a ‘natural’ consequence of being in the uniform of a ‘Guard’ and asserting the power inherent in that role” [20].

The idea that the psychologically stable, upper-middle-class university students selected to work as guards suddenly dreamed and became ill-mannered, savage and rustic and started extending cruel behavior with their peers who by no means had done any harm to them—looks absurd. There is dire need to look for the solid explanation behind the behavior of the guards.

The availability of “The Zimbardo Archive at Stanford University” online in 2018 and its forensic examination by Le Texier [14] has allowed many of the earlier gaps in knowledge about what happened in the study to be filled in.

It is clear that the detailed instructions to the guards were not limited to Saturday’s orientation, introduction of the situational rules and follow-ups of the orientation session but continued to the end of the study. The tyranny exhibited by the guards did not emerge automatically or naturally but by being pushed to be "firm" and "in the action," and empathy levels making them feel authorized to use humiliation and harassment to maintain control.

The second important question is: “Why not all Guards behaved tyrannically”? According to Christina Maslach, there were basically three types of guards: the “tough but fair” (who clearly carried out their role requirements, but did not overstep their boundaries), the “bad guards” (who went beyond their role to act in mean and abusive ways), and the “good guards” (who were nicer to the prisoners and sometimes did little favors for them, like sneaking in a cigarette) [10].

Table 4. Types of Guards

How could the significant difference be explained? It is a critical, although often overlooked, question in discussing details of the SPE: “why not all guards behaved tyrannically”? To get the answer, series of events need to be analyzed critically.

The Principal Investigator emphasized that "The guards have to know that every guard has to be what we call a 'tough guard.' The success of this experiment rides on the behavior of the guards to make it seem as realistic as possible. We need you to act in a certain way. For the time being, we need you to play the role of 'tough guard.' We need you to react as you imagine the 'pigs' would” [1].

But what about guards who were not behaving as they should have? Zimbardo instructed the prison Warden, David Jaffe (one of Zimbardo’s student research associates), to chastise such guards for not being more responsive to the job for which they were getting paid [1—page 65] and to make them more assertive [1— page 81]. For example; Warden Jaffe told one such guard, “The guards have to know that every guard has to be what we call a ‘tough guard.’ The success of this experiment rides on the behavior of the guards to make it seem as realistic as possible’ [1—-page 65].

The “cruel” guards took these instructions to the extreme possibly because of their pre-existing authoritarianism, lower levels of empathy and latent sadistic tendencies. The term “Pathology of Power”, coined by Zimbardo, has interesting background. Whereas at the pre-mature termination of the SPE, the remaining prisoners were delighted, most of the guards seemed to be distressed by this decision. It appeared that they had become sufficiently involved in their role that they had enjoyed the extreme control and power which they exercised as they were “above-reproach”. To Zimbardo the reason for the deterioration in their behavior was power [1]. They started to enjoy this power early in the study (“pathology of power”) as after the first day, the rights of prisoners became redefined as privileges and all privileges were cancelled. Adam Gaisky puts it as: “powerful people roam in a very different psychological space than those without power” [21].

After the end of SPE, Zimbardo interviewed the participants. Here is an excerpt: One guard said: “I was surprised at myself. I made them (prisoners) call each other’s names and clean the toilets out with their bare hands. I practically considered the prisoners cattle, and I kept thinking I had to watch out for them in case they tried something.” Another guard said “Acting authoritatively can be fun. Power can be a great pleasure.” [1].

However, there is another side to the coin. Contrary to the popular interpretation of SPE that power corrupts everyone, American cognitive scientist Scott Barry Kaufman argues that individual differences do matter, and power affects people differently based on their personality. To him the power corrupts but it does not corrupt everyone equally [22]. The great variability in how the guards responded to power was proved in Zimbardo’s analytical report of 2007 when he wrote: “A few guards, who could be classified as "good guards," resisted the temptation of power and were at times considerate of the prisoners' condition. Doing minor nice deeds for the prisoners simply contrasted with the demonic actions of their shift mates.” [1]. Some guards, according to Zimbardo, suffered from the realization of what they had done under the cloak of their role and behind their anonymity-engendering sunglasses. They could see and hear the pain and humiliation they were causing to fellow students who had done nothing to deserve such brutality [1].

While appreciating attitude of the good guards, Serena Chen et al have argued that those with a communal relationship orientation (who take into account other people’s needs and feelings when making a decision) demonstrate greater generosity when given power [23].

The escalation of aggression and abusive behavior, by the guards, was evident due to the positive reinforcement (the introduction of desirable or pleasant stimuli after the performance of a behavior). This reward can be used to further encourage that behavior (or change a pre-existing one) they received both from fellow guards and intrinsically in terms of how good it made them feel to have so much power.

Sarah Carr while challenging Zimbardo’s “Situational Narrative”, argued that the observed behavior was heavily influenced by the roles, expectations, and instructions provided by the researchers. The participants (guards and prisoners) acted according to what they believed the researchers expected of them, rather than purely spontaneous behavior [6].

Later research has challenged the deterministic interpretation of the Lucifer Effect. Not all guards behaved abusively, and some actively resisted cruel behavior, suggesting individual agency and moral choice remained operative [16]. Critics have pointed out that only one third of guards behaved sadistically. This argues against the overwhelming power of the situation. This variance in guard behavior argues against a strict situationist interpretation of the SPE results because such an interpretation cannot account for the clear individual differences observed among the participants. Erich Fromm sums up nicely in his book, “The Anatomy of Human Destructiveness”: “The authors [of the SPE] believe it proves that the situation alone can within a few days transform normal people into abject, submissive individuals or into ruthless sadists. It seems to me that the experiment proves, if anything, rather the contrary. If in spite of the whole spirit of this mock prison which, according to the concept of the experiment was meant to be degrading and humiliating (obviously the guards must have caught on to this immediately), two thirds of the guards did not commit sadistic acts for personal ‘‘kicks,’’ the experiment seems rather to prove that one cannot transform people so easily into sadists by providing them with the proper situation” [24].

Griggs is justified in concluding that the guards’ abusive behavior was largely if not entirely a function of demand characteristics, their doing what they believed they were supposed to do [16]. Whereas a toxic situation can promote cruelty, it does not force everyone to be sadistic because individual morality still acts as a check for many individuals. David Dunaetz argues that the combination of a few sadistic individuals, passive followers, and a leadership that encourages "toughness" (as was the case in SPE) creates a perfect storm for abuse [ 25].

Dehumanization of the Prisoners

“Dehumanization is one of the central processes in the transformation of ordinary, normal people into indifferent or even wanton perpetrators of evil. It is like a cortical cataract that clouds one's thinking and fosters the perception that other people are less than human. It makes some people come to see those others as enemies deserving of torment, torture, and annihilation”. - Philip Zimbardo [1].

The SPE demonstrates how dehumanization and moral disengagement (a psychological process, where individuals detach their moral standards from their actions, allowing them to do unethical things without guilt or self-condemnation) allow individuals to justify immoral actions by displacing responsibility.

During the conduct of SPE, learned helplessness (a psychological state in which individuals, after repeated exposure to uncontrollable negative events, believe they are powerless to change their situation, even when opportunities to do so arise) could explain the prisoners’ submission to the guards. The prisoners learned through negative reinforcement that if they stayed submissive, they may be saved from further humiliation by their peers, working as guards. Zimbardo coined the term “Pathological Prisoner Syndrome” for the social deterioration of the prisoners because of the power play of the “powerful guards”.

Zimbardo himself admits that half of the prisoners had to be released early because of severe emotional and cognitive disorders, transient but intense at the time. Most of those who remained for the duration became mindlessly obedient to the guards' demands and seemed "zombie-like" in their listless movements while yielding to the whims of the ever-escalating guards’ power [1]. This systematic dehumanization had made it easier for the guards to treat the prisoners as “objects” rather than fellow human beings.

Anonymity Shielding and Deindividuation

Whereas the anonymity refers to the state of being unidentified or untraceable, an individual's actions or data cannot be linked to their real-world identity. The present issue is its role in SPE. In SPE, the guards after wearing the uniform similar to that of military, symbolic wooden baton and whistle, reflecting sunglasses to make eye contact impossible and the status of “Mr. Correctional Officer”, started exercising highly authoritative and abusive behavior towards their peers who, just by a flip of coin, had become their subordinates. It is well known that all disguises of one's usual appearance, promoting anonymity, reduce personal accountability. This is what happened in SPE. Leon Festinger (1919-1989), American cognitive psychologist, along with colleagues Albert Pepitone and Theodore Newcomb, formally introduced the concept of deindividuation in their 1952 study, "Some Consequences of De-individuation in a Group". The theory explores how, within a group or crowd, individuals often lose their sense of self-awareness and personal accountability, leading them to engage in behaviors they might not opt otherwise [26].

Zimbardo suggested that de-individuation occurs when people who are part of a relatively anonymous group, lose their personal identity and consequently their inhibitions in relation to violence. This is how group dynamics and peer pressure can lead individuals to conform to group norms, even when they contradict personal morals. This could be explained by crowd psychology. Gustave Le Bon (1841–1931), a French social psychologist, is widely considered the founder of crowd psychology and was the first to systematically analyze how individuals' behavior changes within a crowd [27].

According to Zimbardo deindividuation may explain the behavior of the guards who may have been so sadistic because, to them, it was a group norm. They also may have lost their sense of personal identity because of the uniform they wore.

While uniforms and numbers were used, in SPE, to foster a sense of anonymity (key to deindividuation), the behavior observed was more closely linked to obedience to authority and conforming to assigned roles than a loss of individual identity. The guards, through “orientation”, were instructed to be tough, suggesting that their behavior was driven by situational pressure and authority rather than purely deindividuated crowd mentality. SPE has highlighted how the system support can compel individuals to act against their moral convictions.

The Evil of Inaction Syndrome: Passive Bystanders

“Throughout history, it has been the inaction of those who could have acted; the indifference of those who should have known better; the silence of the voice of justice when it mattered most; that has made it possible for evil to triumph”.- Haile Selassie (1892-1975) - Emperor of Ethiopia.

The Evil of Inaction Syndrome, passive tolerance or condoning of evil through failure to act or intervene, is a psychological and ethical concept defined as the failure of "good" people to act in the face of recognized wrongdoing, injustice, or suffering. While "active evil" involves direct harm, "passive evil" occurs when individuals have the power to intervene but choose not to, often due to perceived apprehensions and, at times, “devil-may-care” sort of attitude. Such a possibility on their part allows evil to thrive just as much as, or more than, the actions of active perpetrators. The SPE was crucial in understanding bystander effects because not all prison guards were hostile to the inmates in the mock prison. They had the ability to reverse the torturous actions of their peers but opted not to do so. It was a pity that no intervention was ever attempted by the good guards to make a positive change in the miserable attitude of bad guards.

According to the Principal Investigator, the best good guard Geoff, shared the night shift with the worst guard Hellmann. Geoff simply suffered in silence along with the prisoners. Had he energized his conscience into constructive action, this good guard might have had a significant impact in mitigating the escalating abuse of the prisoners in his shift [1].

Researcher Bias: Dual Role of Zimbardo

“Time had dimmed my memory of the extent of creative evil in which many of the guards engaged, the extent of the suffering of many of the prisoners, and the extent of my passivity in allowing the abuses to continue for as long as I did—an evil of inaction”.- Philip Zimbardo [1].

The dual role of Zimbardo as “The Principal Investigator” and “The Prison Superintendent” was significantly impactful. Keith argues that Zimbardo with both the positions, produced a conflict of roles whereby he lost sight of the harm being done to the participants – in effect he undermined his own competence to conduct the study, competence of the researcher being somewhat belatedly recognized as a key ethical issue [28]. Zimbardo, while playing both the roles, became emotionally invested and delayed halting the experiment. This is what he himself admitted [1].

Zimbardo narrated an incident in which the mother of one prisoner complained to him about plight of her son. In response, Zimbardo spontaneously activated his “, Institutional Authority Role” and challenged her observation, implying that there must have been a personal problem with her son, not an operational problem with the prison [1].

Carr argues that the action on the part of Zimbardo blurred the line between researcher and participant, influencing the outcome [6]. She is very right because Zimbardo later admitted his own guilt in "the sin of omission", acting more as a Prison Superintendent than a Neutral Researcher which contributed to the out-of-control nature of the situation [1]. In an attempt to justify his roles, he argues “that some situations ‘essentialize’ the roles people are assigned; each person must be what the role demands when he is on that stage set………….I too became The Prison Superintendent in walk, talk, and distorted thought when I was in that place”. [1]. However, at a later date he wrote: “It was not until much later that I realized how far into my prison role I was at that point that I was thinking like a Prison Superintendent rather than a Research Psychologist” [ 1].

Recollecting his reaction and that of the Warden when the guards turned to them for help after the rebellion started, Zimbardo admits: “we backed off and made it clear that their decisions would prevail. We were observers who did not want to intrude” [1]. On another page of the same 2007 Book, he says: “Finally, when most (prisoners) give in and few rebel, the rebels can be considered heroes for resisting the powerful forces toward compliance, conformity, and obedience. They are a special breed who organize their lives around a humanitarian cause, for example” [1]. What a contrast!

On another occasion, he is courageous enough to admit “I would like to believe that had someone else been playing the superintendent's role, I would have seen the light and blown the whistle sooner. I now realize that there should have been someone with authority above mine, someone in charge of oversight of the experiment” ………………….. “However, neither the members of the Human Subjects Research Committee nor I imagined in advance that any such external authority was necessary in an experiment where college students had the freedom to stay or go anytime the going became rougher than they could handle” [1].

Christina Maslach who had the credit of convincing Zimbardo to terminate the SPE prematurely agues: “the lesson learnt for long-running studies like the SPE, there needs to be some sort of clearly defined ‘outside’ system, like trained ombudspersons, who check in regularly to see what is happening, as they will be in a better position to spot anything going wrong “ [10].

It is important to point out that in BBC Prison Study 2002, unlike SPE, the researchers (Haslam and Reicher) took no leadership role in the study [29]. They did not dictate their guards to subjugate the prisoners to their will (in the way that Zimbardo did) with the result that the guards’ and prisoners’ behavior diverged markedly from that in the SPE. It was inferred that people do not automatically assume roles that are given to them, as is suggested by Zimbardo’s situationist account of the SPE, and that tyranny arises from a complex process in which group failure and powerlessness lead group members to identify with authoritarian regimes and their leaders [30].

Updates on Ethics Issues Modeled on SPE

“The SPE is considered one of the most important psychological experiments, not for what it helped reform, but for what it pointed out about the importance of safety for research participants”. Leo Novack [13].

Amendment in the Public Health Service Act

1.        The SPE played a pivotal role in shaping modern ethical standards, contributing to stricter Institutional Review Board (IRB) oversight and the emphasis on participant autonomy and beneficence.

2.        On May10,1973, a Bill (HR 7724) to amend the Public Health Service Act was introduced in House of Congress. After completion of all the actions, it was signed by US President on July 12,1974 and got the status of Public Law 93-348 the same day. The Official Title as Enacted is: “An Act to amend the Public Health Service Act to establish a Program of National Research Service Awards to assure the continued excellence of biomedical and behavioral research and to provide for the protection of human subjects involved in biomedical and behavioral research and for other purposes”. [31].

Key changes were made through the aforesaid Act and the evolution of the APA Ethics Code [32] which is built on several core principles that serve as the foundation for ethical research. Here are the key principles:

         i.            Beneficence and Nonmaleficence

        ii.            Fidelity and Responsibility

      iii.            Integrity

      iv.            Justice

        v.            Respect for People’s Rights and Dignity

3.        According to the Association of Psychological Science, the SPE is now famously cited as a "cautionary tale" highlighting the necessity of rigid ethical protocols for human subjects. [33]

4.        The research guidelines valid in August 1971 and in July 1973 were revised to prohibit human-subject simulations modeled on the SPE. “No behavioral research that puts people in that kind of setting can ever be done again in America," Zimbardo says [34].

CONCLUSION

“The SPE highlighted some important but uncomfortable truths about human behavior, by serving as a powerful demonstration study (rather than an “experiment” per se)” Prof.Christina Maslach [10].

This review sets out to reassess the theoretical foundation of the Lucifer Effect, to evaluate the methodological and ethical weaknesses of the Stanford Prison Experiment, and to draw lessons for contemporary research practice. Taken together, the evidence examined in this paper supports three conclusions.

First: Zimbardo's situational account is not sufficient on its own. The behaviors observed in the SPE cannot be attributed to the prison setting in isolation, since the guards' conduct was shaped throughout by orientation instructions, ongoing direction from the research team, and the expectations participants formed about what was wanted of them. The marked variation among guards, ranging from those who enforced rules without cruelty to those who became actively abusive, further shows that situational pressure did not act uniformly on every individual. It demonstrates that personality, leadership cues, and group dynamics mediated how that pressure was expressed. The Lucifer Effect therefore retains value as a description of how ordinary people can be drawn into harmful conduct, but it should be read as one factor among several rather than a complete explanation.

Second: the methodological weaknesses of the SPE substantially limit what can be claimed from it. The absence of a control group, the small and homogeneous sample, and the blurring of the line between observing behavior and directing it all weaken the inference that what occurred in the basement of the Stanford University psychology building reflected spontaneous role adoption rather than the structure the experimenters built around it. These limitations do not erase the study's historical importance, but they mean its findings function better as a case study and a warning than as established scientific fact.

Third: the ethical record of the SPE rather than settled, and this paper has treated it as such. Judged against an absolute standard of participant protection, the deception involved in the arrests, the failure to halt the study after the first signs of severe distress, and the discomfort created by Zimbardo's dual role as principal investigator and prison superintendent are difficult to defend. Judged against the standards and approvals available in 1971, the study followed the procedures expected of it at the time. Both positions are defensible, and the more useful conclusion is the one the field eventually drew from the dispute: the SPE became the reason simulations of this kind are no longer permitted, and it remains the clearest illustration of why a researcher should never also hold authority over the people being studied.

Taken together, these three points reframe rather than dismiss the SPE’s legacy. Its lasting contribution is not a definitive finding about human nature under conditions of power, but a demonstration of how research design, institutional oversight, and individual moral agency can interact to produce harmful outcomes. The practical lesson is clear: design, oversight, and individual conscience must each be treated as a shared responsibility.

STATEMENTS

Authors’ Contribution

Both the authors made substantial contributions to the conception and design of the study, acquisition of data, analysis, and interpretation of data, drafting the article, revising it critically for important intellectual content, and final approval of the version to be submitted.

Ethical Considerations

The authors declare that the conducted research is not related to either human or animals' use.

Funding Statement

The authors declare that they did not receive any financial support, from any quarter, for the research, authorship, and/or publication of this paper.

Conflict of Interest

Both the authors declare that there is no duality of interest related to the present study.

ACKNOWLEDGEMENT

The authors are highly grateful to Dr. Murad Ahmad Khan for his input, throughout the conduct of study, to improve quality of manuscript.

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