Prisons are brutal places in which all kinds of violent behaviors are part of everyday life. Is this brutality the result of the presence of violent criminals and sadistic guards concentrated in one place? That is, is such behavior caused by the unique personality characteristics exhibited by the types of people thought to be found in prisons (according to stereotypes, at least)? After learning about Milgram’s obedience experiments, you probably are beginning to realize that there might be other explanations for these behaviors. You probably now could suggest the possibility that the social situations found in prisons are defined by the participants in certain ways — ways that cause them to sometimes act in a more aggressive manner. Thus, just as in Milgram’s study, people in prisons may adopt particular social roles that lead them to act, think, and feel in particular ways.
In 1971, Philip Zimbardo and several colleagues tested this claim. Their main goal was to see the degree to which the social roles adopted in prisons affect behaviors, cognitions, and emotions. The idea for the study originated in an undergraduate social-psychology course taught by Zimbardo at Stanford University. He divided the class into study groups of about ten to fifteen students and asked them to investigate various topics. One of these topics involved the effects of prisons on those who lived or worked within them. The group given this topic decided to investigate it by simulating a prison environment. Over the course of one weekend, they maintained a mock (simulated) prison in the basement of a student dormitory. Some students played the part of prisoners and others played the part of guards. The simulation worked well, perhaps too well. The “guards” seemed to take their roles very seriously. Zimbardo (1975) stated that,
[by] the end of the weekend some long-term friendships were broken because those young men and women who were prisoners believed that in their roles as ‘mock’ guards the ‘true’ self of their former friends were revealed, and they could no longer befriend such sadistic authoritarian people. (p. 37)
Zimbardo and his students could not understand what had happened. Why had this simulation, this “game,” become so serious? Was there something unique about the individuals who made up this group — some terrible personality quirk that caused them to act sadistically—or was there something about the social situation being simulated that caused them to behave as they did? In other words, would most people put into that situation behave in similar ways?
In 1971, Zimbardo and several of his colleagues performed a research study designed to answer these questions. Their participants were college students’ from around the country, many of whom were visiting the San Francisco area for the summer. Measurements of the students personalities were made in order to assess relevant attitudes, as well as past experiences and behaviors. Zimbardo and his colleagues chose research participants based on these responses: only those who exhibited no obvious tendencies toward criminal or violent behavior, and no evidence of serious mental disorders, were allowed to participate. The participants were paid $15 per day for taking part in an experiment that was to last two weeks. Zimbardo argued that, because he had excluded people with obviously abnormal personalities and then had randomly assigned the remaining people to play the roles of either guards or prisoners, he would be able to conclude that the resulting behaviors in the mock prison were caused by the social situation and the social roles they had assumed.
When first learning about this study, some of my students arguethat Zimbardo and his colleagues could have studied real prisoners and real guards in an actual prison situation. They state that the researchers could simply have asked these prisoners and guards why they act as they do in particular situations. But think carefully about this argument. Although such a study definitely would have high external validity (because it would take place in a natural situation), it would have low internal validity for two reasons:
- Effects of personality. People who already are prisoners and guards might have personality traits that caused them, in part, to take on these real-life social roles. Personality traits, therefore, are extraneous variable that need to be excluded in order to show the effects of the social situation.
- Unconscious influences. The social roles people take on affect our behavior unconsciously. Thus, we are unlikely to be aware of the situational influences on their behavior.
A simulated prison was constructed in the basement of the psychology building at Stanford University. Zimbardo and his colleagues attempted to simulate a natural prison environment as closely as possible because they did not know which factors in that situation might be important. The simulation even included the “prisoners” being arrested at their homes by officers from the Palo Alto City Police Department (Stanford University is located in Palo Alto, which is a city about 25-30 miles from San Francisco). The simulation was so real that many of the participants were uncertain at first whether this was an actual arrest or part of the experiment:
A police officer charged them with suspicion of burglary or armed robbery, advised them of their legal rights, handcuffed them, thoroughly searched them (often as curious neighbors looked on) and carried them off to the police station in the rear of the police car. At the station they went through the standard routines of being fingerprinted, having an identification file prepared and then being placed in a detention cell. [In the only difference from an actual arrest, each] prisoner was blindfolded and subsequently driven by one of the experimenters and a subject-guard to our mock prison…. Upon arrival at our experimental prison, each prisoner was stripped, sprayed with a delousing preparation (a deodorant spray) and made to stand alone naked for a while in the cell yard. (Haney, Banks, & Zimbardo, 1973, p. 4)
In order to make the participants feel less like unique individuals, they were dressed in uniforms befitting each role:
For the guards, the uniform consisted of plain khaki shirts and trousers, a whistle, a police night-stick…, and reflecting sunglasses…. The prisoners’ uniform consisted of a loose fitting muslin smock with an identification number on front and back, no underclothes, a light chain and lock around one ankle, rubber sandals and a cap made from a nylon stocking. (p. 4)
The prisoner uniform was designed specifically to eliminate the masculine identity of the wearers:
The prisoner uniforms resembled smocks or dresses, which made them look silly and enabled the guards to refer to them as ‘sissies’ or ‘girls’. Wearing these uniforms without any underclothes forced the prisoners to move and sit in unfamiliar, feminine postures. (p. 8)
The ten prisoners who participated in the study were kept in the prison 24 hours per day, whereas the eleven guards had eight-hour work shifts (three guards for each shift) and then could leave to go back to their homes. The prisoners were housed in three “cells” (three per cell) and had no privacy. In Zimbardo’s instructions to the guards, he stressed the fact that physical abuse of the prisoners would not be tolerated. Other than this, Zimbardo gave few instructions about how to behave: he wanted to see how deeply the guards would get into the roles on their own. The prisoners had been told that, although some of their basic civil rights would be suspended during the study, they would not be physically harmed and would be provided an adequate diet, clothing, medical care, and housing.
Once in the prison, the prisoners quickly became upset about their treatment. Their distress was apparent in their negative emotions, a generally negative outlook, and negative evaluations of themselves and their environments. In fact, five prisoners had to be released within a few days after the study began, four of them for depressive symptoms such as crying, rage, and anxiety. The remaining prisoner developed a severe rash that may have been due to stress. Guards also showed more negative emotions, self-evaluations, and a generally negative outlook. Nevertheless, many of them also seemed to enjoy the power of their roles. In fact, they were always on time for their shifts, and would sometimes stay for several hours after their shifts were over without extra pay and without complaint.
Some individual differences emerged among both the prisoners and the guards that seemed to reflect the unique personalities of the participants. In general, there seemed to be three kinds of guard:
- Sadistic guards. Some guards acted sadistically by trying to humiliate the prisoners.
- Tough guards. Some guards enforced the rules in a tough manner but usually did not try to humiliate the prisoners.
- Permissive guards. Some guards exerted little control over the prisoners, and some of them would do small favors occasionally for the prisoners.
There also seemed to be more than one kind of prisoner, although these differences weren’t as obvious since almost many prisoners, after the first few days, became passive, depressed, and obedient. In fact, about half of the prisoners developed symptoms of severe emotional disturbance. Nevertheless, two prisoners were consistently rebellious. One of these rebellious prisoners was discharged on the second day because of an extreme emotional reaction to the simulation. In general, there seemed to be two kinds of prisoner:
- Rebellious prisoners. Two prisoners were consistently defiant, although, in both cases, the rebellious behavior was maintained for only about a day.
- Obedient prisoners. About half of the prisoners became excessively obedient, apparently as a way to avoid punishment from the guards.
There was overlap among these prisoner categories, with some fitting into more than one category depending on the day.
These differences within the prisoner group and within the guard group seemed to reflect personality differences, especially among the guards. These differences, however, were expressed in ways consistent with the participants’ assigned social roles: not one participant stepped outside of the social role he had voluntarily assumed. For example, although there were guards who seemed to feel sorry for the prisoners and would even try to help them occasionally, none of them ever intervened to stop the humiliating tactics of the more sadistic guards.
Perhaps the most disturbing reaction was an increase in group cohesiveness among the guards — they tended to stick together with respect to the abuse of prisoners — and a disintegration of group cohesiveness among the prisoners. The guards acted as one unit of oppression, whereas each isolated prisoner, lacking any hope of effective rebellion (because he would not be supported by the other prisoners) had almost no choice but to submit to the guards’ authority. In fact, many of the prisoners sided with the guards when one of the rebellious prisoners went on a “hunger strike” (refused to eat). As a consequence of the guards’ virtually absolute power, they became increasingly abusive, and the prisoners became increasingly passive. In fact, as was also the case with most participants in Milgram’s obedience study, most guards assumed little or no responsibility for the suffering of the prisoners:
[M]any guards continued to intensify their harassment and aggressive behavior even after the second day of the study, when prisoner deterioration became marked and visible and emotional breakdowns began to occur…. When questioned after the study about their persistent affrontive and harassing behavior in the face of prisoner emotional trauma, most guards replied that they were “just playing the role” of a tough guard, although none ever doubted the magnitude or validity of the prisoners’ emotional response. The reader may wish to consider to what extremes an individual may go, how great must be the consequences of his behavior for others, before he can no longer rightfully attribute his actions to “playing a role” and thereby abdicate responsibility. (Haney, Banks, & Zimbardo, 1973, p. 6)
What is surprising about the prison study, and what makes it different from Milgram’s study, is that the guards abused the prisoners even though no authority figure was present to encourage or command them to do it. That is, once they had defined themselves as prison guards, they seemed impelled by these roles to act accordingly. Surprisingly, the guards saw Zimbardo and the other researchers as being too soft, and tried to conceal some of their more-abusive behaviors from them.
The moral of the Stanford Prison Study seems to be this: when a social situation become “internalized” — when it is “brought within” a person to such an extent that it affects how that person perceives herself and her surroundings (including other people) — the person’s role in that situation determines many of her behaviors, cognitions, and emotions. This moral is illustrated in the diary entries of one person who was assigned the guard role. Before the study, he had written that he could not “see a time when I might … maltreat other living things” because he thought of himself as opposed to the use of coercive force under any circumstances. He also thought that the study was going to be only a fun game that no one would take seriously. After the study began, however, his thinking and behavior quickly changed:
First day: Feel sure that the prisoners will make fun of my appearance and [I decide on] my first basic strategy — mainly not to smile at anything they say or do which would be admitting it’s all only a game….
Second day: Number 5704 asked for a cigarette and I ignored him — because I am a nonsmoker and could not empathize…. Meanwhile since I was feeling empathetic toward #1037, I determined not to talk with him…. After we had count and lights out [another guard] … and I held a loud conversation about going home to our girlfriends and what we were going to do to them.
Third day: (Preparing for the first visitors’ night.) After warning the prisoners not to make any complaints unless they wanted the visit terminated fast, we finally brought in the first parents. I made sure I was one of the guards on the yard because this was my first chance for the type of manipulative power that I really like — being a very noticed figure with almost complete control over what is said or not….
Fifth day: The real trouble starts at dinner. The new prisoner (416) [one of the rebellious prisoners] refuses to eat his sausage … we throw him into the Hole [a solitary-confinement cell] ordering him to hold sausages in each hand…. We decide to…tell the new one that all the others will be deprived of visitors if he does not eat his dinner…. I am very angry at this prisoner for causing discomfort and trouble for the others. I decided to force-feed him, but he wouldn’t eat. I let the food slide down his face. I didn’t believe it was me doing it. I hated myself for making him eat but I hated him more for not eating. (Zimbardo, 1975, pp. 48-49)
These entries suggest that, rather than feel as if the prisoners were human beings worthy of respect (his pre-experiment attitude), he identified so completely with his prison-guard role that he now saw the prisoners as sub-human. Zimbardo concluded that everyone, including himself as the “prison superintendent,” were transformed by their social roles — that their identities were determined to a large extent by their roles. This transformation led to increasingly abusive behaviors on the part of the guards and almost complete passivity and obedience on the part of the prisoners.
Zimbardo observed all this abuse and initially thought of it only as proof that the study was a success. He reported that he did not become aware of how bad the situation had become until his fiancée expressed how upset she was about the sadistic treatment of the prisoners. At that point, only six days into what was supposed to be a two-week experiment, Zimbardo reluctantly ended it:
[W]e had to close down our mock prison because what we saw was frightening. It was no longer apparent to most of the subjects (or to us) where reality ended and their roles began. The majority had indeed become prisoners or guards, no longer able to clearly differentiate between role playing and self. There were dramatic changes in virtually every aspect of their behavior, thinking and feeling. In less than a week the experience of imprisonment undid (temporarily) a lifetime of learning; human values were suspended, self-concepts were challenged and the ugliest, most base, pathological side of human nature surfaced. We were horrified because we saw some boys (guards) treat others as if they were despicable animals, taking pleasure in cruelty, while other boys (prisoners) became servile, dehumanized robots who thought only of escape, of their own individual survival and of their mounting hatred for the guards. (Zimbardo, 1972; quoted in McIntyre, 1999, p. 114)
The guard whose diary entries were quoted above stated that he was “elated” that the study had ended early, but that he also was “shocked to find some other guards disappointed somewhat because … they are enjoying themselves” (p. 49). This person did not seem to remember that he also had been enjoying his power and that he had used this power to humiliate prisoners. Somehow, he was able to act in sadistic ways and (it seems) still see himself as a pacifist.
You may want to read this summary of what we have learned from the Milgram and Zimbardo studies.
Study Questions for Section 6-9
- What classroon project inspired Zimbardo and his colleagues to perform the Stanford Prison experiment?
- What hypothesis was Zimbardo and his colleagues testing?
- Why did they not use an actual prison situation to test this hypothesis?
- How did they control for the effects of personality?
- What did they do to make their prison simulation as real as possible?
- What did they do to make sure the participants became immersed in their assigned roles?
- What individual differences emerged in those assigned to the guard role?
- What individual differences emerged in those assigned to the prisoner role?
- What happened with respect to “group cohesiveness” in the prisoners and in the guards?
- In what way did the cruel behaviors of the guards in Zimbardo’s study differ from the cruel behaviors of the Teachers in Milgram’s study? Why, do you think, did this difference between the two studies occur?
- What is the “moral” of the Stanford Prison Study mentioned above?
- In what ways did the thinking of the prison guard who kept a diary change over the course of the experiment? Why did his thinking change?
- Why did Zimbardo end the study eight days before it was supposed to end?
Haney, C., Banks, W. C., & Zimbardo, P. G. (1973). Study of prisoners and guards in a simulated prison. Naval Research Reviews, 9, 1–17. Washington, DC: Office of Naval Research. Retrieved November 25, 2011, from http://tinyurl.com/yap9qqx
McIntyre, L. J. (1999). The practical skeptic: Core concepts in sociology. Mountain View, CA: Mayfield.
Zimbardo, P. (1972). The pathology of imprisonment. Society, 9, 4-8.
Zimbardo, P. G. (1975). On transforming experimental research into advocacy for social change. In M. Deutsch & H. Hornstein (Eds.), Applying Social Psychology: Implications For Research, Practice, and Training (pp. 33-66). Hillsdale, NJ: Lawrence Erlbaum.