The Stanford Prison Experiment

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Podcast Transcript

In the summer of 1971, Stanford professor of psychology Philip Zimbardo conducted an experiment to determine if cruelty amongst people of authority was because of the position or the people. 

Twenty-four men were selected and randomly assigned roles of guard or prisoner. 

The results were shocking and are still being debated over 50 years later. 

Learn more about the Stanford Prison Experiment, one of the most controversial experiments ever conducted, on this episode of Everything Everywhere Daily.


A major question that psychologists have had is how it is possible for some people to act so cruelly when they are given positions of authority. 

There have been countless examples of humans who otherwise were relatively normal, who acted with an absolute lack of humanity when placed in a role with authority over others.

A good example would be the guards who worked at concentration camps in Nazi Germany. Those people engaged in unspeakable acts they would never have engaged in. A more recent example would be the guards at the Abu Ghraib Prison, who tortured and humiliated the people they were assigned to guard. 

There are many cases of teachers, police officers, guards, and many others who have abused their positions to behave cruelly where they might otherwise never have. 

The big question was if the people attracted to these positions were cruel, to begin with, or does the nature of the position make them cruel? 

One psychologist wanted to conduct a test to see what the answer was. Philip Zimbardo was a professor of psychology at Stanford University in the early 1970s. His idea was to create a mock prison in the basement of the Stanford psychology department building.

He would recruit volunteers to take part in the experiment, and they would randomly be assigned the role of a guard or a prisoner. The plan was to run the prison for two weeks to see how the assigned roles determined the behavior of the volunteers.

Zimbardo placed a classified ad in the Palo Alto newspaper that read:

Male college students needed for psychological study of prison life. $15 per day for 1–2 weeks, beginning Aug. 14. For further information and applications, come to room 248, Jordan Hall, Stanford University.

They received 75 inquiries and then narrowed down the pool to 24 men. They excluded those with a criminal record or with psychological or physical problems. 

Half of the group were assigned to be guards, and half were assigned to be prisoners. Nine in each group were selected, and three in each group were to be alternates. 

The prison cells were 6 feet by 9 feet or 1.8 meters by 2.7 meters, and each held three prisoners. The cells contained a cot for sleeping and sheets. 

The guards were assigned wooden clubs, uniforms, and sunglasses. They also had access to special areas in the basement prison that the prisoners couldn’t access. Perhaps most importantly they had a special orientation meeting the day before it started, where they were told that they couldn’t injure the prisoner nor withhold food or drink. More on this in a bit. 

The experiment began with the help of the Palo Alto police department. They went to the homes of all of the men assigned as prisoners and mock arrested them. The participants did not know that this was going to happen. 

The prisoners were all taken to the local police station, fingerprinted, mug shots taken, and strip-searched. They were then assigned prison clothing with a number and taken to the mock jail on the Stanford campus in a police car with the sirens wailing. 

At all times during the experiment, the prisoners were to be referred to only by their number, not by their names. 

The first day, August 15, went without incident. However, the prisoners were already staging a rebellion as soon as 2 am on the 16th. They didn’t like how they were woken up and rebelled by refusing to eat, ripping the numbers off of their clothes, and insulting the guards.

The guards responded by using a fire extinguisher on the prisoners, putting them in solitary confinement, and taking away their beds.

By day three, the guards began humiliating the prisoners and forced them to use a bucket in their cells to go to the bathroom….and they wouldn’t let them empty the bucket. 

On day four, the guards began dividing the prisoners to get them to work against each other, giving some rewards and other punishments. 

Day five was scheduled to be a day where prisoners could be visited. The guards made the visitors wait far longer than necessary just to be difficult. Several members of the Stanford psychology department visited and expressed concerns about the ethics of the experiment. Almost everything had been recorded, and there was video footage of the guards making the prisoners wear bags on their heads.

On day six, given the concerns of his colleagues and the parents of the prisoners, as well as the increasingly cruel behavior of the guards, Zimbardo ended the experiment a week early. 

Two of the prisoners had withdrawn from the test before it had ended.

They held a debriefing with everyone, paid them their money for the full fourteen days, and everyone was invited back a week later to get their thoughts on the experiment.

The Stanford Prison Experiment went on to become probably the most famous psychological experiment in history and has been the subject of many papers and books. It is also taught in most introductory courses on psychology. 

According to Zimbardo, the experiment showed that people would conform to their assigned roles. The guards became crueler, and the prisoners became more passive and acquiescent. 

This conclusion fit with past experiments, which showed a similar pattern of behavior. A previous experiment, known as the Milgram Experiment, asked people to shock a subject they could hear but not see with increasing levels of electricity. The Milgram Experiment will be the subject of a future episode.

That, at least, is the standard explanation that has been given for the last fifty years. 

However, since the experiment was run, and even in the middle of it, other psychologists have had problems with the experiment and its conclusions. 

For starters, one of the biggest objections was the ethics of the experiment. The men assigned as prisoners had no idea what they would be subject to. The prisoners were told they could leave at any time, but that wasn’t the case. The experiment continued even after some prisoners expressed a desire to leave. 

Beyond just the ethics, there were many problems with the experiment itself. 

For starters, it wasn’t really an experiment. There was no variable that was being controlled. There wasn’t another group running a similar experiment that was holding a variable constant. 

Another problem is the fact that it wasn’t really a prison. The guards and prisoners knew that this was just an experiment, that it would end relatively soon, and that they’d get paid for their participation. No one could really get hurt, and there was no real danger. 

There is something known as the Hawthorne effect, which says that people will change their behavior when they know they are being watched. Almost all of the interactions in the mock prison were recorded on film. 

Years later, when interviewed about the experiment, both the guard and prisoner participants admitted that they were just acting out what they thought the experimenters wanted to see. One of the guards later said, “I believed that I was doing what the researchers wanted me to do.”

One of the prisoners who had a meltdown and was released early, Douglas Korpi, later admitted he thought he’d be able to study for an exam while in the prison. When he found out he couldn’t, he threw a fit to get released so he could go and study. He said,  “.If you listen to the tape, it’s not subtle. I’m not that good at acting. I mean, I think I do a fairly good job, but I’m more hysterical than psychotic.”

Douglas Korpi today is a forensic psychologist. 

There was one guard who was considered the cruelest. He was nicknamed John Wayne because he had a southern accent. His real name was Dave Eshleman. 

Eshleman had studied acting and didn’t actually have a southern accent. He later said, “I took it as a kind of an improv exercise….I believed that I was doing what the researchers wanted me to do, and I thought I’d do it better than anybody else by creating this despicable guard persona. I’d never been to the South, but I used a southern accent, which I got from Cool Hand Luke.”

Perhaps most damning of all was research done by a French filmmaker by the name of Thibault Le Texier. He went back and actually listened to the original tape recordings of the experiment, which were in the Stanford University Archives. 

What the guards were told to do in the orientation meeting was vastly different from what Zimbardo had told everyone for years. He told the guards, “We cannot physically abuse or torture them….(but) We can create boredom. We can create a sense of frustration. We can create fear in them, to some degree… We have total power in the situation. They have none.”

So they weren’t just told to keep order. 

In fact, Zimbardo went out of his way to tell Eshleman what a good job he did during the experiment. 

In the 50 years since the Stanford Prison Experiment took place, has anyone tried to replicate it?

Yes, sort of. 


In 2002, the BBC created a four-part documentary series called “The Experiment.” 

They took 15 men and assigned them to guards and prisoners over an eight-day period. None of the cruelty which was seen in the Stanford Prison Experiment was observed.

There was group identification between guards and prisoners, and there was a prison break on the sixth day where the prisoners tried to create a commune, but nothing supported the Stanford Experiment’s conclusions. 

So, if the Stanford Prison Experiment was so badly run, why has it gotten the attention it has? Why are its conclusions still part of every introductory psychology course?

Part of it had to do with the timing of the experiment. Within a month of the experiment’s conclusion, two major prison uprisings took place in San Quentin in California and Attica in New York. 

Prisons were a top news story, and this was something that confirmed what many people wanted to believe. Zimbardo was flown to Washington to testify before Congress about the conclusions of his study. 

As with most scientific studies reported in the news, only the conclusions are usually reported, and no one bothers to investigate the study itself. It took decades before anyone took a deep dive into the archives of the Stanford Prison Experiment to find out what actually happened. 

This isn’t just a problem with this one experiment. There have been a huge number of psychology experiments, many of which are bedrocks of the discipline that can’t be replicated. This has been dubbed the Replication Crisis. 

It also impacts other scientific disciplines, but it has hit psychology the hardest. 

So, the most famous psychological experiment of all time is almost certainly wrong, or at least it is so flawed that it can’t be used to prove its conclusions.  It means in the future, a lot of introduction to psychology textbooks will have to be rewritten. 


Everything Everywhere Daily is an Airwave Media Podcast. 

The executive producer is Darcy Adams.

The associate producers are Thor Thomsen and Peter Bennett.

Today’s review comes from listener MattB over at Podcast Republic. He writes:

Always interesting and informative, first podcast I listen to everyday. I’ve been a member of the completionist club for over a year. Bear’s fans seem to have a rivalry with Gary so I’ll end this review with Skol Vikings!

Thanks, Matt! True story….

I once attended a Packer/Vikings game at the Metrodome with one of my friends who is a Vikings fan. We happened to be sitting a few rows below the luxury box of the then Vikings owner Red McCombs. He had the window to his box open to watch the game.

A woman several rows below us kept trying to get his attention to get him to sign her Vikings jersey, but he ignored her the whole game. 

Eventually, I told her, “hey lady, if you really want a NFL owner to sign your shirt, I’d be happy to do it for you.”

Also, how can you tell a Packer fan from a Viking fan? Answer: the Vikings fan is the one without any rings. 

Remember, if you leave a review or send me a boostagram, you too can have it read on the show.