What You Didn't Know about the Stanford Prison Experiment

Did the infamous Stanford Prison Experiment prove that evil environments produce evil behavior, or were there serious flaws in the experiment?

by Brian Dunning

Filed under General Science

Skeptoid #102
May 27, 2008
Podcast transcript | Listen | Subscribe

It was 1971 when the prisoner, emotionally drained, sleep deprived, chained, and dehumanized in his rough muslin smock was thrown into a tiny dark closet by the cruel guard nicknamed John Wayne, to endure solitary confinement without food or bathroom privileges. You might think this scene was from Hanoi in Vietnam, or at best a military prison in the United States. You'd be close. This brutal activity was funded by the United States Navy, which was interested in learning more about the psychological mechanisms in a prison environment. It took place at Stanford University in California, and the prisoner had done nothing wrong other than to volunteer for a research project. This was the infamous Stanford Prison Experiment, conducted by professor of psychology Dr. Philip Zimbardo.

Philip Zimbardo grew up in what he describes as a "South Bronx ghetto", and as a boy watched his close friends engage in acts of violence, abuse drugs, and wind up in jail. He grew fascinated by the question of why good people do bad things, and became convinced from a very young age that bad environments tend to poison the people placed into them. Put a good person into an evil situation, and that person will become evil. He later wrote:

To investigate this I created an experiment. We took women students at New York University and made them anonymous. We put them in hoods, put them in the dark, took away their names, gave them numbers, and put them in small groups. And sure enough, within half an hour those sweet women were giving painful electric shocks to other women within an experimental setting... Any situation that makes you anonymous and gives permission for aggression will bring out the beast in most people. That was the start of my interest in showing how easy it is to get good people to do things they say they would never do.

From his body of work, it is easy to conclude that he was actively interested in justifying a preconceived notion: That good people will become evil if you put them into an evil environment. About a decade after getting his Ph.D. in psychology from Yale, Zimbardo went to Stanford University, where he got tenure and then set about planning the experiment that was to define his career.

24 students were recruited for a two-week experiment for which they would each receive $15 per day. They were randomly assigned to be either prison guards or inmates. The prisoners were surprised to be picked up unexpectedly at their homes by real Palo Alto police officers. They were roughly hustled to their new home, stripped, deloused, and put into rough muslin smocks with no underwear. Zimbardo described it:

The question there was, what happens when you put good people in an evil place? We put good, ordinary college students in a very realistic, prison-like setting in the basement of the psychology department at Stanford. We dehumanized the prisoners, gave them numbers, and took away their identity. We also deindividuated the guards, calling them Mr. Correctional Officer, putting them in khaki uniforms, and giving them silver reflecting sunglasses like in the movie Cool Hand Luke. Essentially, we translated the anonymity of Lord of the Flies into a setting where we could observe exactly what happened from moment to moment.

The results have become legendary. Some of the guards seemed to relish their newfound authority a little too much, becoming sadistic, and working extra hours just for fun. The torment they put on the prisoners was real. Some began showing physical manifestations of stress and psychological trauma, to the point that one third of them had to be removed from the experiment early. In fact, it got so bad that Zimbardo decided to end the experiment after only six days, less than half the planned duration.

Zimbardo's conclusion was clear. Good, ordinary college students willingly became sadistic tormentors, simply because they were given the permission, the means, and the expectation of doing so. The Stanford Prison Experiment, and this well-publicized result, became a permanent fixture in the popular conception of psychology.

The problem is that a lot of the psychology community disagrees with his findings. Some found that any results were rendered meaningless by insufficient controls. Some have problems with his analysis of the results, reaching a different conclusion based on the same data. Some found the sample population invalidated by selection biases, or the size of the sample inadequate for statistically useful results. Some found methodological flaws that tainted the participants' behavior. Let's look at some of these criticisms in closer detail.

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Dr. Zimbardo and the Stanford Experiment came into the news again in 2004, following the Abu Ghraib prison scandal in Iraq. American prison guards were accused of cruelty to Iraqi prisoners — the great Naked Human Pyramidgate scandal. A number of soldiers and senior officers were court martialed and imprisoned or demoted. The prosecutors claimed that "a few bad apples" were responsible. The defense disagreed, and called in Dr. Zimbardo as an expert witness to testify that it was the environment that was responsible, not the individuals. "You can't be a sweet cucumber in a vinegar barrel," he famously said. The court disagreed, finding (rightly, as many would say) that individuals must be held accountable for their own actions, and the few bad apples went to jail. Dr. Zimbardo then wrote the book The Lucifer Effect, drawing further parallels between his prison experiment and the Abu Ghraib scandal.

Psychology is complicated, and there will probably never be a perfect theory explaining all human behavior; so people should never assign too much significance to the results of any given experiment like the Stanford Prison Experiment. And, when an experiment receives a large amount of scholarly criticism from mainstream science, as this one did, you have very good reason to look past its portrayal in the popular media and, instead, be skeptical.

Brian Dunning

© 2008 Skeptoid Media Copyright information

References & Further Reading

Brannigan, A. The Rise and Fall of Social Psychology: The Use and Misuse of the Experimental Method. New York: Aldine de Gruyter, 2004. 37-39.

Brockman, John. "You can't be a sweet cucumber in a vinegar barrel: A talk with Philip Zimbardo." Edge: The Third Culture. Edge Foundation, Inc., 19 Jan. 2005. Web. 24 Apr. 2008. <http://www.edge.org/3rd_culture/zimbardo05/zimbardo05_index.html>

Carnahan T., McFarland S. "Revisiting the Stanford prison experiment: Could participant self-selection have led to the cruelty?" Personality and social psychology bulletin. 1 May 2007, Volume 33, Number 5: 603-614.

Haney, C., Banks, C., Zimbardo, P. "Interpersonal dynamics in a simulated prison." International Journal of Criminology & Penology. 1 Feb. 1973, Volume 1, Number 1: 69-97.

Reicher, S., Haslam, S. A. "Rethinking the psychology of tyranny: The BBC prison study." British Journal of Social Psychology. 1 Mar. 2006, Volume 45, Number 1: 1-40.

Zimbardo, P. The Lucifer Effect: Understanding How Good People Turn Evil. New York: Random House, 2008.

Reference this article:
Dunning, B. "What You Didn't Know about the Stanford Prison Experiment." Skeptoid Podcast. Skeptoid Media, 27 May 2008. Web. 4 Oct 2015. <http://skeptoid.com/episodes/4102>


10 most recent comments | Show all 69 comments

Thank you for this article. My sociology class just read about and examined this experement.

While I was reading the paper, I came up with some of the very same criticisms you and many in the scientific community came up with.

I found this experement could not be valid as there were too many holes and variables left open in order to make any conclusion.

It is a shame my professor does not even bring out the critical thinking involved with these types of studies and experements. She expects us to believe her. She, like Zimbardo seems to have one view that is extolled and ignores all good criticisms or does not bring them up in order to have a fair chance of thinking the concept through. Despite being a very personable teacher, I find that her lack of critical thinking and expecting us to reach the conclusions that she wants us to makes her a bad professor.

Cari Beth, St Cloud, MN
January 24, 2012 1:22pm

I would be very disinclined to accept the researcher's own response to criticisms, especially given that I do know quite well why the ethics were changed--this was actually covered in part in the process of explaining why.

The information provided on 'John Wayne'--that he was modeling his behavior on a movie character--suggests that at least one of the 'guards' was demonstrating something quite different, in the sense that he was following a model of behavior provided by the media. Even worse, it provides a particularly well-tested alternate explanation of the behavior observed: people were behaving according to the 'scripts' those around them have given them.

Regardless of the overall validity of the theory, screening and controlling for people having already preconceived ideas of what, exactly, would be expected of them in their roles would be essential for ensuring the experiment's validity.

This is also why his involvement as anything more than an observer--and only an observer--is an issue. This adds an aura of authority, at least vaguely, and variations on the original electroshock experiment has demonstrated that this makes a difference.

Regardless of ethical issues, this particular experiment would be unlikely to be repeated as-is because of the lack of controls for error, which would only be amplified by the relatively tiny sample size.

Anon, Somewhere
August 30, 2012 8:41pm

Thanks for doing this episode. A few months ago a friend of mine was recounting his reading of the lucifer effect and how everyone is basically terrible.

I began questioning the experiments accuracy considering that the participants were not a true cross section of the human population.

(My friend did not convey that they were all male students)

I brought up that age, location, employment status, (I had assumed that the volunteers wernt employed) race, and willingness to participate in a study that would take them away from home might skew the results.

My friend acknowledged my skepticism and saw some logic in it. He's an open minded dude.

Anyhow it was great to hear someone who was more farmilliar with the study explain some of the same criticisms with the results and interpretation thereof. Not to mention having been done so eloquently.

Again, thanks man!

Andy, Mesa AZ
February 26, 2013 5:43am

I think that we can all get along if we just get rid of gambling, taboo, and other sins while turning to jesus. amen gurl.

dip-dip, Antananarivo
April 6, 2013 2:23pm

Which taboo did you want to get rid of, dip-dip?

Darren, Liverpool, UK
April 24, 2013 4:18pm

I have commented on this critique before here (2 years ago). The moderator edited out most of my comments about how inaccurate and ill-informed his remarks were and how little he knew about psychology. How very convenient for him. My full criticism can be at https://www.facebook.com/groups/28435826189/permalink/10150531431206190/
You need to be skeptical of the skeptics.

Sharon Presley, Oakland CA
August 18, 2013 11:19pm

Hang on, a facebook entry is considered a fair analysis of psychology or an attempt at a historical skeptoid entry?

That sounds like a lot of wasted breath and effort when a linkable skeptoid critique in the web would have been far more effective.

Should I bother to write an article in future, one that critiques a skeptical entry, I'll go one further and post and refer to twitter so nobody could ever look it up.

Credibility is everything according to the above comment.

Facebook is a social medium for people to meet and greet and air their inexact foibles. Hardly anything anyone would look up or refer to as fair comment.

Manatee Diversion, Greenacres by the sea Oz
September 11, 2013 11:34am

It isn't that bad environment create bad people, it's more like the world is more full of bad people. The guards were only nice in the beginning because they didn't realize they could get away with being bad (so good isn't innate). Once the delusion that they had power sunk in, they began to think they can do whatever they want and is above the prisoners. It wasn't the prison that made the people evil, they were already like that - the prison just gave them some excuse, justification for the act. Truly good human beings are rare.

AX, New York
January 21, 2014 12:57am

Dr. Presley, I found your rebuttal very informative. Brian often advises his listeners not to take his word for it, and to do our own research. In this case I think I shall. I'll have to add Zimbardo and Milgram's books to my reading list.

P.S. I think your original comment might have been edited due to length rather than content.

Cas, Olywa
February 17, 2014 10:55pm

I must admit I am biased concerning the ultimate cause of good/bad behavior in people.

My job is reading police reports. I can't claim any sweeping insights for groups of people under differeing conditions. What I can say about individuals is:

1] There are some children/people who, no matter what you do to the, demonstrate a strong moral character and kindness above and far beyond what could be expected out of such circumstances.

2] There are some children/people who are rotten to the core no matter what you do for them. Does Leopold and Loeb ring any bells?

The only hypothesis I *can* present is: horrible circumstance may not turn a person into a monster (aside from personality distortions that proceed from terminal stressors or a psychotic break), but horrible circumstances will definitely shape the kind of monster one will become if the monster was in there to begin with.

The problem is too complex for a quick answer from any single study even if adequate controls can be devised.

Swampwitch, Gainesville Fl
February 20, 2014 11:48am

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