Stanford Report Online

Stanford Report, August 22, 2001
Thirty years later, Stanford Prison Experiment lives on


Thirty years ago, a group of young men were rounded up by Palo Alto police and dropped off at a new jail -- in the Stanford Psychology Department. Strip searched, sprayed for lice and locked up with chains around their ankles, the "prisoners" were part of an experiment to test people's reactions to power dynamics in social situations. Other college student volunteers -- the "guards" -- were given authority to dictate 24-hour-a-day rules. They were soon humiliating the "prisoners" in an effort to break their will.

Psychology Professor Philip Zimbardo's Stanford Prison Experiment of August 1971 quickly became a classic. Using realistic methods, Zimbardo and others were able to create a prison atmosphere that transformed its participants. The young men who played prisoners and guards revealed how much circumstances can distort individual personalities -- and how anyone, when given complete control over others, can act like a monster.

"In a few days, the role dominated the person," Zimbardo -- now president-elect of the American Psychological Association -- recalled. "They became guards and prisoners." So disturbing was the transformation that Zimbardo ordered the experiment abruptly ended.

Its story, however, endures, achieving a level of recognition shared by few other psychological experiments.

Students played guards and prisoners in an August, 1971 prison experiment that continues to generate interest. Credit: Chuck Painter

"The study is now more in the popular consciousness than it has ever been before," Zimbardo said, attributing part of the recent surge in interest to "reality TV" shows such as Survivor and Big Brother. Because he videotaped many hours of prisoner-guard interaction, Zimbardo has a record of how the individuals changed over time. "It represents a forerunner of reality TV," Zimbardo said.

Website an international hit

Steadily increasing levels of incarceration in the United States also have fueled interest in the experiment. Between 1986 and 1997 alone, the male adult prison population increased by over two-thirds and the female population doubled.

Zimbardo has strong opinions on the harmful effects of harsh prison sentences. "Prisons are evil places that demean humanity. ... They are as bad for the guards as they are for the prisoners," he said, pointing to results of his experiment showing that both guards' and prisoners' personalities were warped by their given roles.

Now students, scholars and activists who want a closer look at those roles have a new resource. While he has been selling an educational video, Quiet Rage: The Stanford Prison Experiment, since 1992, Zimbardo recently has taken some of the photos and video captured during those tense days of 1971 and combined them with text to create a dedicated website,

The site has garnered over 2.4 million page views since its launch in December 1999. On average, people at nearly 330 computers a day view the site. And these viewers stay a long time at the site, many paging through 10 or more screens filled with photos, text and video clips. Scott Plous, a doctoral student of Zimbardo's who is now a psychology professor at Wesleyan University in Middletown, Conn., manages the site along with several other social psychology sites housed on a Wesleyan server with funding from the National Science Foundation.

Plous points to the experiment's lessons about incarceration as particularly valuable. "Globally, many prison systems would benefit from reform. Phil's research has a lot to offer those countries as well as the U.S."

Popular fascination, distortion

What drives much of the fascination with the experiment is the sense that any individual could become a brutal dictator if given the chance. Zimbardo is still surprised at how quickly the participants changed their stripes.

"These guys were all peaceniks," he recalled of the students chosen to be guards. "They became like Nazis.

"It shows how easy it is for good people to become perpetrators of evil."

The experiment has drawn intense interest from the news media, including a 1998 60 Minutes segment.

The dramatic potential of the story -- average men turning into monsters -- has also been exploited in ways so extreme that they distort Zimbardo's work.

Zimbardo says that, without notifying him in advance, earlier this year a German production company released a film titled Das Experiment. It opens with the statement: "The story of this film is inspired by incidents that occurred during a psychological experiment at Stanford University, Palo Alto, California."

What angers Zimbardo is the way the movie's authors used specific elements of his experiment but turned its conclusion into a fictional nightmare. Without explaining that the film's climax deviated from Zimbardo's experiment, some viewers might be left confused about the psychologist's role. Instead of showing the abrupt end of the experiment -- Zimbardo halted it early after only six days -- the film shows guards attacking and raping a female psychologist and committing other fictional acts of mayhem.

Zimbardo said he has received hundreds of e-mails from Germans asking how he could have allowed such things to happen -- even though he didn't.

"It was very disheartening to have them take this story and twist it in a negative way," said Stanford's legal counsel, Deborah Zumwalt, whose office contacted the film's director and producers. "We were very concerned about it."

In response to Zimbardo's and Zumwalt's requests, the film's producers eventually agreed to include a very different disclaimer in future versions, something to tell people that "this is purely fiction," Zumwalt said. But the copies already in distribution haven't been changed.

Zimbardo hopes to block the U.S. distribution of the German movie. He also noted that he is "negotiating for an American made-for-TV movie" about the experiment.

An experiment with legs

"It's this old thing that has legs," Zimbardo remarked about the experiment. For him, those legs took him to the next level in his career. Zimbardo explained that his 1971 discoveries led him to examine another type of prisoner-guard situation: the voices that shy people hear when confronted with social situations. Shy people, he realized, act as their own guards. "The shy person is the quintessential combination of one's own prisoner and guard," said Zimbardo, who went on to found the Shyness Clinic at Stanford in 1975. (The clinic is now located in Menlo Park and is no longer affiliated with the university.)

Another reason the experiment remains fresh is that it would be taboo today.

Zimbardo maintains that the student-participants suffered no long-term harm -- even though some had symptoms of mental breakdown during the experiment. But now, the standards for using human subjects in research wouldn't permit such an experiment, Plous said. "Because of the rules, it's unlikely to ever be replicated," he said.

A "guard" leads a "prisoner" down the hall in a 1971 Stanford psychology experiment. The experiment explored power dynamics by creating false distinctions among college student volunteers. Credit: Chuck Painter