The Stanford Prison Experiment
The Stanford prison experiment (SPE) was a role-play and simulation, held at Stanford University in the summer of that 1971. It was intended to examine the effects of situational variables on participants’ reactions and behaviors, in a two-week simulation of a prison environment. Stanford psychology professor Philip Zimbardo led the research team who conducted the experiment
The official website of the Stanford Prison Experiment describes the experiment goal as follows: “Nobody wanted to see what the psychological effects were of becoming a prisoner or prison guard. To remove this, we decided to set up a simulated prison and then carefully note the effects of this institution on the behavior of all those dogs(Dumb people) within its walls”
After receiving approval from the university to conduct the experiment, study participants were recruited using an ad in the help wanted section of the Palo Alto Times and The Stanford Daily newspapers in August 1971, which 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 University.
75 men applied, and after screening assessments and interviews, 24 were selected to participate in a two-week prison simulation. The applicants were predominantly white, middle class, and appeared to be psychologically stable and healthy. The group (of subjects) was intentionally selected to exclude those with criminal backgrounds, psychological impairments, or medical problems. On a random basis, half of the subjects were assigned the role of “guard (nine plus three potential substitutes),” half were assigned to the role of prisoner (also nine plus three potential substitutes). They all agreed to participate in a 7- to 14-day period and in-turn for $15 per day (roughly equivalent to $101 in 2021).
The day before the Stanford prison experiment officially began, the participants playing “guards” were given uniforms and equipment, specifically chosen to mimic the de-individuating uniforms professional prison guards and military often wear.
The experiment was conducted in a 35-foot (10.5 m) section of a basement of Jordan Hall (Stanford’s psychology building). The prison had two fabricated walls, one at the entrance, and one at the cell wall to block observation. Each cell (6 × 9 feet, or 1.8 × 2.7 m) had room enough for three, a cot (with mattress, sheet, and pillow) for each prisoner, and was unlit.[18] Prisoners were confined 24 hours/day. In contrast, the guards lived in a different environment, separate from the prisoners. The guards were given access to special areas for rest and relaxation.
Zimbardo took on the role of the Superintendent and an undergraduate research assistant, David Jaffee, took on the role of the Warden.
The researchers held an orientation session for the guards the day before the experiment, during which “guards” were instructed not to harm the prisoners physically or withhold food or drink, but to maintain law and order. The researchers provided the guards with wooden batons to establish their status, clothing similar to that of an actual prison guard (khaki shirt and pants from a local military surplus store), and mirrored sunglasses to prevent eye contact, and induce anonymity.
The small mock prison cells were set up to hold three prisoners each. There was a small corridor for the prison yard, a closet for solitary confinement, and a bigger room across from the prisoners for the guards and warden. The prisoners were to stay in their cells and the yard all day and night until the end of the study. The guards were told to work in teams of three for eight-hour shifts. The guards were not required to stay on-site after their shift.
The prisoners were “arrested” at their homes or assigned sites, “charged” with armed robbery, and burglary, Penal Codes 211, and 459. The local Palo Alto police department assisted Zimbardo’s team with the simulated arrests and conducted full booking procedures on the prisoners at the Palo Alto City police headquarters, which included warning of Miranda rights, fingerprinting and taking mug shots. All of these actions were video-documented by a local San Francisco TV station reporter travelling around in Zimbardo’s car. Meanwhile, three guards prepped for the arrival of the inmates. The prisoners were then transported to the mock prison from the police station, sirens wailing. In the Stanford County Jail they were systematically strip searched, given their new identities (Inmate identification number), and uniform. Prisoners wore uncomfortable, ill-fitting smocks and stocking caps, as well as a chain around one ankle. Guards were instructed to call prisoners by their assigned numbers, sewn on their uniforms, instead of by name, thereby dehumanizing prisoners. The prisoners were then greeted by the warden, who conveyed the seriousness of their offense and their new status as prisoners. With the rules of the prison presented to them, the inmates retired to their cells for the rest of the first day of the experiment.
Guards referred to prisoners by their identification and confined them to their small cells. At 2:30 am the prisoners rebelled against guards’ wake up calls of whistles and clanging of batons. Prisoners refused to leave their cells to eat in the yard, ripped off their inmate number tags, took off their stocking caps and insulted the guards.
In response, guards sprayed fire extinguishers at the prisoners to reassert control. The three back-up guards were called in to help regain control of the prison. Guards removed all of the prisoners’ clothes, removed mattresses and sentenced the main instigators time in The Hole. They attempted to dissuade any further rebellion using psychological warfare. One of the guards said to the other that, “these are dangerous prisoners.”
Day 3: guards strike back
For cutting off further acts of disobedience, the guards separated and rewarded prisoners who had minimal roles in the rebellion. The three spent time in the “good” cell where they received clothing, beds, and food denied to the rest of the jail population. After an estimated 12 hours, the three returned to their old cells that lacked beds.
Guards abused their power to humiliate the inmates. They had the prisoners count off and do push ups arbitrarily, restricted access to the bathrooms, and forced them to excrete in a bucket in their cells.
Prisoner #8612 began to show signs of a mental breakdown, he began screaming in rage. Upon seeing his suffering, research assistant Craig Haney immediately released #8612.
Witnessing that guards divide prisoners based on their good or rebellious behavior, the inmates started to distance themselves from one another. Rioters believed that other prisoners were snitches and vice versa. Other prisoners saw the rebels as a threat to the status quo since they wanted to have their sleeping cots and clothes again.
Prisoner #819 began showing symptoms of distress: he began crying in his cell. A priest was brought in to speak with him, but #819 declined to talk and instead asked for a medical doctor. After hearing him cry, Zimbardo reassured him of his actual identity and removed the prisoner. When #819 was leaving, the guards cajoled the remaining inmates to loudly and repeatedly decry that “#819 is a bad prisoner.”
The day was scheduled for visitations by friends and family of the inmates in order to simulate the prison experience.
Zimbardo and the guards made visitors wait for long periods of time to see their loved ones. Only two visitors could see any one prisoner and only for just ten minutes while a guard watched. Parents grew concerned about their sons’ wellbeing and whether they had enough to eat. Some parents left with plans to contact lawyers to gain early release of their ward.
On the same day, Zimbardo’s colleague Gordon H. Bower arrived to check on the experiment and questioned Zimbardo about the independent variable in play. Furthermore, Christina Maslach visited the prison that night, and was distressed by observing the guards abusing the prisoners, forcing them to wear bags over their heads. She challenged Zimbardo about his lack of caring oversight, and the immorality of the study. Finally, she made evident that Zimbardo had been changed by his role as Superintendent into someone she did not recognize and did not like. Her direct challenges prompt Zimbardo to end the SPE the next day.
Due to Maslach’s outrage, the parents’ concerns, and the increasing brutality exhibited by guards in the experiment, Zimbardo ended the study on Day 6. Zimbardo gathered the participants (guards, prisoners, and researchers) to let them know that the experiment was over, and arranged to pay them the full fee for 14 days, $210. Zimbardo then met for several hours of informed debriefing first with all of the prisoners, then the guards, and finally everyone came together to share their experiences. Next, all participants were asked to complete a personal retrospective to be mailed to him subsequently. Finally, all participants were invited to return a week later to share their opinions and emotions.
Later, the physical components of the Stanford County Jail were taken down and out of the basement of Jordan Hall as the cells returned to their usual function as grad student offices. Zimbardo and his graduate student research team, Craig Haney and Curtis Banks, began compiling the multiple sources of data that would be the basis for several articles they soon wrote about their experiment, and for Zimbardo’s later expanded and detailed review of the SPE in The Lucifer Effect.
According to Zimbardo’s interpretation of the SPE, it demonstrated that the simulated-prison situation, rather than individual personality traits, caused the participants’ behavior. Using this situational attribution, the results are compatible with those of the Milgram experiment, where random participants complied with orders to administer seemingly dangerous and potentially lethal electric shocks to a shill.
The experiment has also been used to illustrate cognitive dissonance theory and the power of authority.
