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?
Filed under General Science
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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.
- First, the issue of selection bias. Selection bias is where you choose your subjects in such a way that they are not truly representative of the general population. In this case, Zimbardo advertised to students to participate in an experiment about "prison life". Clearly, a large segment of the general population would be repulsed by such a concept, and you've got to have questions about anyone attracted to that idea. Thus, all applicants to the Stanford Prison Experiment were preselected for comfort with the idea of "prison life".
- Most of the Stanford guards did not exhibit any cruel or unusual behavior, often being friendly and doing favors for the prisoners. The most notorious guard, nicknamed John Wayne, explained that he was simply trying to emulate Strother Martin's character from Cool Hand Luke. Other analysts have found it difficult to support Zimbardo's conclusions, since the allegedly poisonous environment did not affect most participants, and the most notorious participant explained that his motivation came from a completely different source.
- Zimbardo himself was also criticized for actively participating in the experiment as one of the characters. He was the prison superintendent. Although he may have restrained himself from having any influence on the experiment, the fact that he put himself in the position of ultimate active authority over the guards' behavior calls this into question. Many designers of such experiments would summarily throw out such a study based on this alone.
- Some researchers have also questioned why Zimbardo neglected the effect of individual personalities, instead generally attributing all behavior to the prison environment. How did John Wayne's behavior as a guard compare to his behavior outside the experiment? Was he generally a friendly guy, or might he already have been a royal jerk? We don't know, so there was insufficient data to conclude that his behavior was changed by the experiment.
- The statistical validity of the sample of participants, 24 male Stanford students of about the same age, has been called into question as being too small and restrictive to be generally applicable to the population at large.
- I have one other issue with Zimbardo's results that I didn't find anyone else raising, and it goes back to my 15-point checklist in Skeptoid #37, How to Spot Pseudoscience. Zimbardo has dedicated much of his career to the promotion of the idea that bad environments drive bad behavior. I tend to be cautious of claims coming from sources dedicated to promoting them. The scientific method starts with a null hypothesis, not with a preconceived notion to justify; and that process invariably produces data that do not support the conclusion, and theories tend to change over time as a result. By my analysis, Zimbardo appears to be cherrypicking his results to justify the same conclusion that he has been promoting throughout his career. This doesn't make him wrong, it just gives me cause for skepticism.
- Finally, It's worth mentioning that by today's standards, the Stanford Prison Experiment was unethical and could never be performed in the United States. However, this point is not relevant to the validity of the results, and in any event, it was perfectly legal at the time.
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.
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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.
Reference this article:
Dunning, Brian.
"What You Didn't Know about the Stanford Prison Experiment." Skeptoid Podcast. Skeptoid Media, Inc.,
27 May 2008. Web.
2 Sep 2010. <http://skeptoid.com/episodes/4102>
Discuss!
5 most recent comments | Show all 49 comments
Remember, you should always read with skepticism the comments of anyone too lame to put their real name & city.
I think Zimbardo has stated many many times that he was way off with the Stanford Prison Experiment. The ethics were bad and the whole experiment went wrong from the beginning with Zimbardo being both the supervisor and prison's superintendent.
I feel the remarkable finding is itself that the experiment got so far off hands. Zimbardo writes the following on his own website:
"...perhaps the most important was simply this: The simulation became so real, and the guards became so abusive, that the experiment had to be shut down after only 6 days rather than the two weeks planned."
On his book, The Lucifer Effect, he also states that the experiment was inhuman "the findings came at the expense of human suffering. I am sorry for that and to this day apologize for contributing to this inhumanity." (pp. 181, 235)"
There are many infamous experiments in the history of social psychology. Many of them are inaccurate or not up to the scientific standards of today.
I feel that there is definitely a group, role, deindividuation, environment, authority, circumstances -or what ever you want to call it - factor in human decision making and acting.
Again, in my personal view, I don't see Zimbardo denying the individual's responsibility in doing bad things. But he does state that the individual decision is widely affected by the circumstances (possibly more in the narrow experiments than in real life).
Otso, Helsinki, Finland
February 15, 2010 2:06pm
“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.”
You make it sound like he set out to prove a point, maybe even unethically. That’s not fair. Like any good researcher, Zimbardo was simply interested in a specific topic area. The scientific method, used correctly, would prevent any bias from affecting his findings.
The fact that one of the worst guards, the so-called John Wayne, took his cue from a movie character says little about his willingness to use the behaviors of that character to mask, or even to justify, his bullying of the prisoners. It also says nothing about the other 1/3 of guards who took their cue from him and also abused the prisoners.
“Some researchers have also questioned why Zimbardo neglected the effect of individual personalities, instead generally attributing all behavior to the prison environment.”
I don’t know why they’d ask that. Obviously, it wasn’t the purpose of the study.
In science, we try to eliminate “individual personalities” (aka, extraneous variables) specifically so that they WON’T interfere in the study. As long as the subjects were randomly assigned to the role of prison guard, we can be relatively certain what caused their behavior. That’s Research Methods 101.
The static you're finding in the field of Psych boils down to an age-old debate between Situationalists and Dispositionalists.
Sheldon W. Helms, San Ramon, CA
April 17, 2010 9:23am
Before writing my own review of the Lucifer Effect as part of a blog entry I checked what others had to say about him and was surprised to find that it was almost all positive without much if any criticism. This surprised me since I found many problems with it and what looked like a clear conflict of interest. Zimbardo seems to be doing research for reasons other than what he initially claims and I suspect he almost certainly wasn’t a sincere opponent of the Viet Nam war as he claims. His focus seems to be studying ways to use authority and other methods to manipulate people and although he has partly admitted to this he is still doing more to manipulate people for the wrong reasons. Tour criticism was an exception. You seem to be the only person I’ve found that provided a better review of it so far. However even though I don’t agree with everything Zimabardo wrote I do believe that the situation is part of the explanation but not all of it and even though he had preconceived ideas to prove some of them were partially true. If any one is interested in the other comments I had about Zimbardo or a truth and education commission see the following blog entry (discussion about Zimbardo is on the second half):
http://zakherys.tripod.com/nonviolence/index.blog/2003131/truth-and-education-commission/
Zach Taylor, Boston Mass
April 19, 2010 9:15am
“Most of the guards did not exhibit any cruel behavior... the alleged poisonous atmosphere did not affect most participants.” This is factually incorrect and misleading. It is NOT true that most participants were not affected. Quoting from The Lucifer Effect (TLE): “Half of our student prisoners had to be released early because of severe emotional and cognitive disorders, transient but intense at the time. Most of those who remained for the duration generally became mindlessly obedient to the guards’ demands and seemed ‘zombie-like’ in their listless movements while yielding to the whims of the ever-escalating guard power.”
“As with the rare ‘good guards,’ so too, a few prisoners were able to stand up to the guards’ domination...Clay-416, who should have been supported for his heroic passive resistance, instead was harassed by his fellow prisoners for being a ‘troublemaker.’ They adopted the narrow dispositional perspective provided by the guards rather than generate their own metaperspective on Clay’s hunger strike as emblematic of a path for their communal resistance.” [p. 196) The video of the experiment bears out this observation.
As for the guards, about one-third did engage in cruel behavior, about a third were neutral and did nothing in the face of appallingly cruel behavior that, under other circumstances, no reasonable person would have tolerated (e.g., forcing the prisoners to make homosexual advances in crude and graphic language).
[From a longer response...]
Sharon Presley, Oakland CA
May 22, 2010 8:13pm
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I have my doubts that the experiment was perfectly legal because a real Palo Alto Police Officer unexpectedly handcuffed the prisoners in front of where they lived. The prisoners only expected to get into the police car. No crime was committed so the handcuffing was completely outrageous. Is it perfectly legal for a real uniformed police officer to publicly handcuff innocent people in a realistic way? The handcuffing generates most of the interest because many people find it extremely entertaining. There are some shades of sadism here. The handcuffing is a likely breach of any consent for four reasons. First, the Palo Alto Police and the news media camera teams knew about the arrests and handcuffing but the prisoners didn’t. Second, it destroyed anonymity because the name and addresses of the prisoners became widely known. Third, it was public spectacle that had nothing to do with “no privacy” as was likely included in the consent. Fourth, the study into prison life was to take place on campus ensuring the anonymity of the participants. What do public arrests have to do with prison life? It’s obvious the neighbors and others could exactly figure out who was who in the Stanford film and photographs given that the prisoners were clearly identified. This badly hurt the future lives of the young prisoners. The public handcuffing was detrimental in the long term because the prisoners felt a need to continually explain it as part of an experiment. Every aspect of this experiment was brutal to the prisoners. In a study document a psychologist says that the guards were “to realize if the prisoners escaped the study would be terminated.” It was impossible for any of the prisoners to walk out because
Harold, Tampa, FL
February 11, 2010 4:08pm