In an attempt to discover whether human nature is inherently good or evil, Philip Zimbardo and his team of researchers conducted an experiment in which two dozen young men played roles as prisoners and guards in a mock prison. The actions of the participants shocked not only researchers but also the participants themselves. The experiment, which was to last fourteen days, ended after only six days because of prisoner abuse and dehumanization.
The Stanford prison experiment was a psychological study in role-playing that divided subject-volunteers into incarcerated prisoners and working guards in a mock prison. Within the first few days of the experiment, the guards became physically abusive, even sadistic, toward the prisoners. After a planned prison break and the emotional breakdown of more than one participant, the experiment was ended. Although originally designed to last two weeks, the research was terminated prematurely, after only six days.
Twenty-four healthy, middle-class young men were selected from those who responded to a newspaper advertisement asking for volunteers for a prison-simulation experiment. By a flip of a coin the twenty-four volunteers were divided into two groups, comprising twelve prisoners and twelve prison guards. Nine guards and nine prisoners started the experiment and the others were held on reserve in case their services were needed. Those who were designated prisoners were “arrested” by real police officers, fingerprinted, booked, and then brought to a simulated prison built in the basement of the psychology building at Stanford University. They then were stripped, deloused, and issued a smock to wear as part of their prison uniform. Prisoners were given numbers in place of names and were forced to wear a ball and chain at all times to remind them they could not escape. To further add to the anonymity, the prisoners’ heads were covered with nylon-stocking caps to simulate shaven heads.
The prison guards were given a khaki uniform, a whistle, a nightstick, and a pair of mirrored sunglasses that prevented the prisoners from seeing his eyes. Guards were expected to work one of three eight-hour shifts throughout the day but were otherwise given very little guidance as to how to fulfill their roles. The warden and guards prepared a list of rules for their prison that included the decrees that prisoners were to address each other by their numbers only and that the guards were always to be referred to as Mr. Correctional Officer or Mr. Chief Correctional Officer. To help prisoners accept their situation as reality, they were forbidden to make reference to the experiment or simulation.
The guards were quick to tell the prisoners that they would be punished if they did not obey the rules. In no time, the guards learned to assert their authority over the prisoners. For example, they forced them to do push-ups, sometimes with the weight of other prisoners on their backs, and denied them basic privileges, such as using the toilet.
On the morning of the second day the prisoners had had enough of the experiment. They barricaded themselves in their cells, removed their stocking caps, and removed the numbers from their smocks. The guards responded by calling in the three reserve guards, ending the prisoner rebellion. They stripped the prisoners, removed their cots, and began to taunt them. To prevent future outbreaks the guards decided to design a special-privilege cell, in which certain prisoners were allowed to eat while the others, temporarily denied food, watched. This privilege decreased the solidarity among the prisoners and increased the prison guards’ bond for keeping control.
Hence, the experiment began to affect the prison guards as well, and the prisoners seemed more willing to submit to the guards’ abuse. The guards started to believe that the prisoners were a threat to their authority. Throughout the six days of the experiment, the guards steadily became more aggressive in their punishment, dehumanization, and humiliation of the prisoners. One prisoner was released after only thirty-six hours because he began to suffer from an acute emotional disturbance, or breakdown.
The prisoners had responded to their situation in a variety of ways. Some tried to obey all the rules and do exactly as the guards told them. Others rebelled and fought the system. One prisoner acquired what he said was a rash after learning that his request for parole had been denied. More and more prisoners began to suffer emotionally, and some cried.
In a period of five days, the prison witnessed several other incidents, including the following: Prison guards had neutralized the threat of a prison break twice; all the prisoners had come before a parole board and were denied parole; the prison had a parents’ visitation day; and a clergyman was brought in to talk to the prisoners. Guards who had never been late for a shift had become sadistic in their attempts to control the prisoners, and the prisoners themselves were withdrawing and experiencing mental and emotional trauma. It was on the fifth day that researchers were clear that the study had to end.
On the sixth and final day of the experiment, prisoners, guards, and staff met to discuss the simulation. Many said they were startled by how quickly prisoners were dehumanized, and the guards told researchers that their sense of human value was destroyed—if just temporarily. The power each guard was given transformed that guard from a benign Dr. Jekyll to an evil Mr. Hyde.
As might be expected, the volunteer prisoners expected to be harassed, receive a minimally adequate diet, and lose some of their rights. Indeed, the volunteers were informed of these consequences in the consent agreements they signed before the start of the experiment. However, no one could predict how rapidly and how considerably the guards and prisoners would adjust to the roles expected of them and to internalize their power, or lack thereof. Zimbardo would attribute three underlying conditions that led to the extreme internalization of those prescribed roles: indistinguishable prisoners, lack of accountability, and anonymity among guards.
In his later work, Zimbardo continued to study how good people become wicked when put in positions of authority. Although the Stanford prison experiment has never been replicated, by Zimbardo or any other researchers, parallels have been drawn between this study and real-life incidents of the abuse of power, such as in Nazi Germany or at
The true impact of this study has been debated in academic circles. Some argued that the experiment proves human nature is not as benign as society wishes to believe. Others note the lack of an independent variable and believe that the experiment was fatally flawed. Similarly, the morality of this experiment has sparked controversy. Finally, modern consent laws and erring on the side of protecting research subjects in academic studies likely would prevent a replication of the Stanford experiment.
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Haney, C., and P. G. Zimbardo. “The Past and Future of U.S. Prison Policy: Twenty-five Years After the Stanford Prison Experiment.” American Psychologist 53 (1998): 709-727. A reflection on the Stanford prison experiment and a look at penal system changes in the wake of Zimbardo’s research. -
Schwartz, J. “Simulated Prison in ’71 Showed a Fine Line Between ’Normal’ and ’Monster.’” The New York Times, May 6, 2004. Schwartz compares the experience in Abu Ghraib prison to the historical experiments conducted by Milgram and Zimbardo. -
Zimbardo, P. G. The Lucifer Effect: Understanding How Good People Turn Evil. New York: Random House, 2007. Zimbardo revisits his 1971 experiment and applies his research to the torture and humiliation of Iraqis held by the U.S. military at Abu Ghraib prison, challenging society to think about the situational influences that led to oppression and abuse. -
Zimbardo, P. G., C. Maslach, and C. Haney. “Reflections on the Stanford Prison Experiment: Genesis, Transformations, Consequences.” In Obedience to Authority: Current Perspectives on the Milgram Paradigm, edited by Thomas Blass. Mahwah, N.J.: Erlbaum, 2000. This chapter explores the Stanford prison experiment as complementary to analyses of the Milgram experiments.
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