Philip Zimbardo: Experiment & Lucifer Effect

Instructor: Natalie Boyd

Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.

Philip Zimbardo spent 4 decades studying why people do bad things to each other. Learn about the Stanford Prison Experiment and the book, The Lucifer Effect, which seeks to answer why people treat others poorly using the abuses of Iraqi prisoners by the U.S. as an example. Updated: 02/04/2022

Why do good people do bad things? How can entire groups of people - civilians, soldiers, teachers, neighbors - hurt others? Why do things like the Nazi movement or the abuses at the Abu Ghraib prison happen? Social scientist Philip Zimbardo has spent the past 40 years studying those very questions, and he thinks he has the answers.

The Stanford Prison Experiment

In 1971, Zimbardo was a young professor at Stanford University and dating a graduate student named Christina Maslach. He was interested in studying the ways that power dynamics and social roles influence human behavior. He created a fake prison in the basement of Jordan Hall at Stanford and divided 24 male college students into 'prisoners' and 'guards.' The plan was for the students to live in the 'prison' for two weeks while Zimbardo and his colleagues observed the way the subjects behaved. They hoped the information would help them understand the subtleties of real prisons.

Philip Zimbardo in 1975
Philip Zimbardo in 1975

Zimbardo told the guards to keep the prisoners in line but not to use physical violence. On the second day of the experiment, the prisoners revolted, and the guards began to use extreme tactics to control them, including (at various times) putting paper bags over their heads, making them strip down naked, and forcing them to clean toilets with their bare hands. As the experiment continued, the situation escalated. Many of the prisoners began to show severe signs of trauma. Five of the prisoners had to be released early.

Neither Zimbardo nor his fellow researchers had any plans to stop the experiment early, despite the behavior of the subjects; however, on the fifth day, Maslach came to visit the fake prison. Alarmed by what she saw, Maslach told Zimbardo, 'I think it is terrible what you are doing to those boys!' The two of them argued, but eventually Zimbardo came to agree with Maslach that the experiment was doing harm to the subjects, and on the sixth day (eight days early) he terminated the experiment.

Later, Zimbardo recognized his own role in the pain the experiment caused, writing, 'I was guilty of the sin of omission - the evil of inaction… I am sorry for that.'

The Lucifer Effect

In 2007, Zimbardo published a book called The Lucifer Effect. In it, he explores what causes good people to do horrible things. The first two-thirds of the book is his retelling of the Stanford Prison Experiment, including the discoveries about human behavior and the ethical implications of the experiment. The last few chapters explore the history of human atrocities and explain them in light of the psychological lessons learned from the Stanford Prison Experiment.

Jordan Hall at Stanford University, where the prison experiment took place
Jordan Hall, Stanford University

The Lucifer Effect, named for God's favored angel who fell from grace, is a theory that describes how good people can do terrible things. In the book by the same title, Zimbardo explains the compilation of elements that makes it possible for good people to hurt others. One key element of the Lucifer Effect is that of dehumanization, which happens when some people are seen as less than human and not worth compassion. Another important component of the Lucifer Effect is the desire for conformity. When others around you are doing bad things, you might also do them in order to fit in. Even Maslach felt peer pressure; when she first viewed the Stanford Prison Experiment, she wasn't sure if she should say anything, because the other researchers didn't think anything was wrong.

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