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The Stanford Prison Experiment

Now a major film, to be released this week, decades after the “experiment.”

By Philip Zimbardo

Forty-four years ago, I conducted a research experiment that could have been the bane of my existence. Instead, what has become known as the Stanford prison experiment (SPE) drove me to extensively pursue the question: Why do good people do evil things? After three decades of research on this subject, I recorded my findings in The Lucifer Effect: Understanding How Good People Turn Evil (Random House, 2007). But the SPE also lead me to study why, in difficult situations, some people heroically step forward to help others – oftentimes complete strangers - while others stand by and watch. The psychological time warp experienced by participants of the SPE – not knowing if it was day or night or what day it was - lead to my research in our individual time perspectives and how these affect our lives. Rethinking shyness as a self-imposed psychological prison led me to conduct research on shyness in adults, and then create a clinic in the community designed to cure shyness.

The Experiment in a Nutshell

In August 1971, I lead a team of researchers at Stanford University to determine the psychological effects of being a guard or a prisoner. The study was funded by the US Office of Naval Research as both the US Navy and the US Marine Corps were interested in the causes of conflict between military guards and prisoners. In the study, 24 normal college students were randomly assigned to play the role of guard or inmate for two weeks in a simulated prison located in the basement of the Stanford Psychology Department building. But the guards quickly became so brutal, and I had become so caught up in my role as superintendent, that the experiment had to be shut down after only six days.

Challenging the Truth

There seems to be powerful silent barriers to dealing with new truths emanating from psychological laboratories and field experiments that tell us things about how the mind works, which challenge our basic assumptions. We want to believe our decisions are wisely informed, that our actions are rational, that our personal conscience buffers us against tyrannical authorities, and also in the dominating influence of our character despite social circumstances. Yes, those personal beliefs are sometimes true, but often they are not, and rigidly defending them can get us in trouble individually and collectively. Let’s see how.

Denial and Finger Pointing

When we discover two of three ordinary American citizens administered extreme electric shocks to an innocent victim on the relentless commands of a heartless authority, we say, “no way, not me.” Yale University psychologist Stanley Milgram’s obedience to authority research has been in the public arena for decades, yet we ignore its message of the power of unjust authority in undercutting our moral conscience. Similarly, the SPE research made vivid the power of hostile situational forces in overwhelming dispositional tendencies toward compassion and human dignity. Still, many who insist on honoring the dominance of character over circumstance reject its situational power message.

In 2004, people around the world witnessed online photos of horrific actions of American Military Police guards in Iraq’s Abu Ghraib Prison against prisoners in their charge. It was portrayed as the work of a “few bad apples” according to military brass and Bush administration spokesmen. I publicly challenged this traditional focus on individual dispositions by portraying American servicemen as good apples that were forced to operate in a Bad Barrel (the Situation) created by Bad Barrel Makers (the System). I became an expert witness in the defense of the Staff Sergeant in charge of the night shift, where all the abuses took place. In that capacity I had personal access to the defendant, to all 1000 photos and videos, to all dozen military investigations, and more. It was sufficient to validate my view of that prison as a replica of the Stanford prison experiment—on steroids, and my defendant, Chip Frederick, as a really Good Apple corrupted by being forced to function 12-hours every night for many months in the worse barrel imaginable. My situation-based testimony to the military Court Martial hearings helped reduce the severity of his sentence.

“The Stanford Prison Experiment” Film

On July 15, The Stanford Prison Experiment premiers in New York City. The Los Angeles premier – as well as nationwide release is scheduled for July 17. The film stars Billy Crudup as me and Olivia Thrilby as Christina Maslach, the whistle-blowing graduate student (whom I later married) who pointed out the experiment had gone awry and had changed me to such a degree that she didn’t know who I was anymore. In January, The Stanford Prison Experiment received two awards at the Sundance Film Festival: best screenwriting and best science feature.

What is special about the The Stanford Prison Experiment movie is the way it enables viewers to look through the observation window as if they were part of the prison staff watching this remarkable drama slowly unfold, and simultaneously observe those observers as well. They are witnesses to the gradual transformations taking place, hour- by- hour, day- by- day, and guard shift- by- guard shift. Viewers see what readers of The Lucifer Effect book account can only imagine. As these young students become the characters inhabited in their roles and dressed in their costumes, as prisoners or guards, a Pirandellian drama emerges.

The fixed line between Good, like us, and Evil, like them, is relentlessly blurred as it becomes ever more permeable. Ordinary guys soon slip into doing extraordinarily bad things to other guys, who are actually just like them except for a random coin flip. Other healthy guys soon get sick mentally, being unable to cope with the learned helplessness imposed on them in that unique, unfamiliar setting. They do not offer comfort to their buddies as they break down, nor do those who adopt a “good guard” persona ever do anything to limit the sadistic excesses of the cruel guards heading their shifts.

Finally, the movie also tracks the emotional changes in the lead character—me-- as his compassion and intellectual curiosity get distilled and submerged over time. The initial roles of research creator-objective observer are dominated by power and insensitivity to prisoner suffering in the new role of Prison Superintendent. The six-day process of transformations in the original experiment is crunched down to 2 hours, but the magic of the movie’s acting, directing and editing psychologically expands that time frame’s full force. We feel the power of social situations dominating personalities; as viewers are encouraged to ponder:

What kind of Guard would I be?
What kind of Prisoner? What kind of Superintendent?
And would I have blown the whistle to end this drama sooner, or not?

My hope is that this movie can do what my writings about this special research into human nature have not been fully able to do. Perhaps now viewing and reliving this adventure will enable the general public to better appreciate the value of what “research shows” about mind, behavior and the pervasive power of situational forces.

Here is a recent Huffington Post interview that includes the movie trailer:​…?

Visit the official Stanford Prison Experiment website to learn more about the experiment that inspired the film: www.

Heroic Imagination

Phil Zimbardo
Source: Phil Zimbardo

I should add that along with continuing research in time perspectives and time perspective therapy, my new mission in life has been to empower everyone to wisely resist negative situational forces and evil by becoming Everyday Heroes in Training. Our non-profit Heroic Imagination Project (HIP) teaches ordinary people how to stand up, speak out and take effective actions in challenging situations in their lives.

Working and learning together, we can create a new generation of ordinary everyday heroes who will do extra-ordinary deeds of daily heroism in their families, schools, businesses, and communities.


Phil Zimbardo


Learn more about yourself and how to cope with stress and anxiety, visit

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