Biography of Philip Zimbardo

The Legacy of His Famous "Stanford Prison Experiment"

AOL BUILD Speaker Series: 'The Stanford Prison Experiment'
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Philip G. Zimbardo, born March 23, 1933, is an influential social psychologist. He is best known for the influential—yet controversial—study known as the “Stanford Prison Experiment,” a study in which research participants were “prisoners” and “guards” in a mock prison. In addition to the Stanford Prison Experiment, Zimbardo has worked on a wide range of research topics and has written over 50 books and published over 300 articles. Currently, he is a professor emeritus at Stanford University and president of the Heroic Imagination Project, an organization aimed at increasing heroic behavior among everyday people.

Early Life and Education

Zimbardo was born in 1933 and grew up in the South Bronx in New York City. Zimbardo writes that living in an impoverished neighborhood as a child influenced his interest in psychology: “My interest in understanding the dynamics of human aggression and violence stems from early personal experiences” of living in a rough, violent neighborhood. Zimbardo credits his teachers with helping to encourage his interest in school and motivating him to become successful. After graduating from high school, he attended Brooklyn College, where he graduated in 1954 with a triple major in psychology, anthropology, and sociology. He studied psychology in graduate school at Yale, where he earned his MA in 1955 and his PhD in 1959. After graduating, Zimbardo taught at Yale, New York University, and Columbia, before moving to Stanford in 1968.

The Stanford Prison Study

In 1971, Zimbardo conducted his most famous and controversial study—the Stanford Prison Experiment. In this study, college-age men participated in a mock prison. Some of the men were randomly chosen to be prisoners and even went through mock “arrests” at their homes by local police before being brought to the mock prison on the Stanford campus. The other participants were chosen to be prison guards. Zimbardo assigned himself the role of the superintendent of the prison.

Although the study was originally planned to last two weeks, it was ended early—after just six days—because events at the prison took an unexpected turn. The guards began to act in cruel, abusive ways towards prisoners and forced them to engage in degrading and humiliating behaviors. Prisoners in the study began to show signs of depression, and some even experienced nervous breakdowns. On the fifth day of the study, Zimbardo’s girlfriend at the time, psychologist Christina Maslach, visited the mock prison and was shocked by what she saw. Maslach (who is now Zimbardo’s wife) told him, “You know what, it's terrible what you're doing to those boys.” After seeing the events of the prison from an outside perspective, Zimbardo stopped the study.

The Prison Experiment’s Impact

Why did people behave the way they did in the prison experiment? What was it about the experiment that made the prison guards behave so differently from how they did in everyday life?

According to Zimbardo, the Stanford Prison Experiment speaks to the powerful way that social contexts can shape our actions and cause us to behave in ways that would have been unthinkable to us even a few short days before. Even Zimbardo himself found that his behavior changed when he took on the role of prison superintendent. Once he identified with his role, he found that he had trouble recognizing the abuses happening in his own prison: “I lost my sense of compassion,” he explains in an interview with Pacific Standard.

Zimbardo explains that the prison experiment offers a surprising and unsettling finding about human nature. Because our behaviors are partially determined by the systems and situations we find ourselves in, we are capable of behaving in unexpected and alarming ways in extreme situations. He explains that, although people like to think of their behaviors as relatively stable and predictable, we sometimes act in ways that surprise even ourselves. Writing about the prison experiment in The New Yorker, Maria Konnikova offers another possible explanation for the results: she suggests that the environment of the prison was a powerful situation, and that people often change their behavior to match what they think is expected of them in situations such as this. In other words, the prison experiment shows that our behavior can change drastically depending on the environment we find ourselves in.

Critiques of the Prison Experiment

Although the Stanford Prison Experiment has had a significant influence (it was even the inspiration for a film), some people have questioned the validity of the experiment. Instead of simply being an outside observer of the study, Zimbardo served as the prison superintendent and had one of his students serve as the prison warden. Zimbardo himself has admitted that he regrets being the prison superintendent and should have remained more objective.

In a 2018 article for Medium, writer Ben Blum argues that the study suffers from several key flaws. First, he reports that several of the prisoners claimed being unable to leave the study (Zimbardo denies this allegation). Second, he suggests that Zimbardo’s student David Jaffe (the prison warden) may have influenced the behavior of the guards by encouraging them to treat prisoners more harshly.

It’s been pointed out that the Stanford Prison Experiment demonstrates the importance of reviewing the ethics of each research project before the study goes forward, and for researchers to think carefully about the study methods that they use. However, despite the controversies, the Stanford Prison Experiment raises a fascinating question: how much does the social context influence our behavior?

Other Work by Zimbardo

After conducting the Stanford Prison Experiment, Zimbardo went on to conduct research on several other topics, such as how we think about time and how people can overcome shyness. Zimbardo has also worked to share his research with audiences outside of academia. In 2007, he wrote The Lucifer Effect: Understanding How Good People Turn Evil, based on what he learned about human nature through his research in the Stanford Prison Experiment. In 2008, he wrote The Time Paradox: The New Psychology of Time That Will Change Your Life about his research on time perspectives. He has also hosted a series of educational videos titled Discovering Psychology.

After the humanitarian abuses at Abu Ghraib came to light, Zimbardo has also spoken about the causes of abuse in prisons. Zimbardo was an expert witness for one of the guards at Abu Ghraib, and he explained that he believed the cause of events at the prison were systemic. In other words, he argues that, rather than being due to the behavior of a “few bad apples,” the abuses at Abu Ghraib occurred because of the system organizing the prison. In a 2008 TED talk, he explains why he believes the events occurred at Abu Ghraib: “If you give people power without oversight, it's a prescription for abuse.” Zimbardo has also spoken about the need for prison reform in order to prevent future abuses at prisons: for example, in a 2015 interview with Newsweek, he explained the importance of having better oversight of prison guards in order to prevent abuses from happening at prisons.

Recent Research: Understanding Heroes

One of Zimbardo’s most recent projects involves researching the psychology of heroism. Why is it that some people are willing to risk their own safety to help others, and how can we encourage more people to stand up to injustice? Although the prison experiment shows how situations can powerfully shape our behavior, Zimbardo’s current research suggests that challenging situations don’t always cause us to behave in antisocial ways. Based on his research on heroes, Zimbardo writes that difficult situations can sometimes actually cause people to act as heroes: “A key insight from research on heroism so far is that the very same situations that inflame the hostile imagination in some people, making them villains, can also instill the heroic imagination in other people, prompting them to perform heroic deeds.” 

Currently, Zimbardo is president of the Heroic Imagination Project, a program that works to study heroic behavior and train people in strategies to behave heroically. Recently, for example, he has studied the frequency of heroic behaviors and the factors that cause people to act heroically. Importantly, Zimbardo has found from this research that everyday people can behave in heroic ways. In other words, despite the results of the Stanford Prison Experiment, his research has shown that negative behavior isn’t inevitable—instead, we are also capable of using challenging experiences as an opportunity to behave in ways that help other people. Zimbardo writes, “Some people argue humans are born good or born bad; I think that’s nonsense. We are all born with this tremendous capacity to be anything.”


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Hopper, Elizabeth. "Biography of Philip Zimbardo." ThoughtCo, Aug. 27, 2020, Hopper, Elizabeth. (2020, August 27). Biography of Philip Zimbardo. Retrieved from Hopper, Elizabeth. "Biography of Philip Zimbardo." ThoughtCo. (accessed May 31, 2023).