12.2.4 Zimbardo’s Stanford Prison Experiment

The famous Stanford prison experiment, conducted by social psychologist Philip Zimbardo and his colleagues at Stanford University, demonstrated the power of social roles, social norms, and scripts. In the summer of 1971, an advertisement was placed in a California newspaper asking for male volunteers to participate in a study about the psychological effects of prison life. More than 70 men volunteered, and these volunteers then underwent psychological testing to eliminate candidates who had underlying psychiatric issues, medical issues, or a history of crime or drug abuse. The pool of volunteers was whittled down to 24 healthy male college students. Each student was paid $15 per day (equivalent to about $80 today) and was randomly assigned to play the role of either a prisoner or a guard in the study. Based on what you have learned about research methods, why is it important that participants were randomly assigned?

A mock prison was constructed in the basement of the psychology building at Stanford. Participants assigned to play the role of prisoners were “arrested” at their homes by Palo Alto police officers, booked at a police station, and subsequently taken to the mock prison. The experiment was scheduled to run for several weeks. To the surprise of the researchers, both the “prisoners” and “guards” assumed their roles with zeal. On the second day of the experiment, the guards forced the prisoners to strip, took their beds, and isolated the ringleaders using solitary confinement. In a relatively short time, the guards came to harass the prisoners in an increasingly sadistic manner, through a complete lack of privacy, lack of basic comforts such as mattresses to sleep on, and through degrading chores and late-night counts.

The prisoners, in turn, began to show signs of severe anxiety and hopelessness—they began tolerating the guards’ abuse. Even the Stanford professor who designed the study and was the head researcher, Philip Zimbardo, found himself acting as if the prison was real and his role, as prison supervisor, was real as well. After only six days, the experiment had to be ended due to the participants’ deteriorating behavior. Zimbardo explained,

At this point it became clear that we had to end the study. We had created an overwhelmingly powerful situation—a situation in which prisoners were withdrawing and behaving in pathological ways, and in which some of the guards were behaving sadistically. Even the “good” guards felt helpless to intervene, and none of the guards quit while the study was in progress. Indeed, it should be noted that no guard ever came late for his shift, called in sick, left early, or demanded extra pay for overtime work. (Zimbardo, 2013)

The Stanford Prison Experiment has been used as a memorable demonstration of the incredible power that social roles, norms, and scripts have in affecting human behavior. However, multiple aspects of the study have been subject to criticism since its inception. The nature of these criticisms range from ethical concerns to issues of generalizability (Bartels, Milovich, & Moussier, 2016; Griggs, 2014; Le Texier, 2019). One criticism is that the way students were recruited for the experiment may have impacted the outcome (Carnahan & McFarland, 2007). Another criticism questions the conclusions that can be drawn from the study. Zimbardo appears to have provided specific guidelines of the types of behaviors that were expected of the guards (Zimbardo, 2007). Subsequent research suggests that such guidelines likely created an expectation of the types of behavior that Zimbardo reported observing in the Stanford Prison Experiment (Bartels, 2019), and that given these expectations, the guards simply acted as they thought they were expected to act. It has also been problematic that attempts to replicate aspects of the study have not been successful. For example, when no guidelines were presented to the guards, researchers documented different outcomes than those observed by Zimbardo. (Reicher & Haslam, 2006).

The Stanford Prison Experiment has some parallels with the abuse of prisoners of war by U.S. Army troops and CIA personnel at the Abu Ghraib prison in 2003 and 2004 during the Iraq War. The offenses at Abu Ghraib were documented by photographs of the abuse, some taken by the abusers themselves (Figure 12.10).