The Stanford Prison Experiment is Bullshit

Could Be Wrong
7 min readMay 3, 2020


in 1971, Stanford University’s Philip Zimbardo ran an experiment to see whether the volatile dynamics between prison inmates and their guards were due to the psycho-social circumstances of prisons, or due to the individual dispositions of those within. The experiment was advertised as a ‘psychological study of prison life.’, and 24 middle-class, male college students signed up.

The subjects were randomly assigned the role of inmate or guard and it wasn’t long before the guards demonstrated harassment and violence against the inmates. The experiment that was supposed to run for two weeks ended up being cut short at 6 days.

Zimbardo would have you believe that the subjects lost touch of reality and swapped out their old identities for comparatively violent new ones. I’m not so sure.

Carlo Prescott, who had served 17 years for attempted murder, acted as Zimbardo’s ‘prison consultant’, and after seeing how Zimbardo had used the experiment to explain atrocities that had taken place in real prisons, rebuked him with a 2005 article titled ‘The Lie of the Stanford Prison Experiment’:

… ideas such as bags being placed over the heads of prisoners, inmates being bound together with chains and buckets being used in place of toilets in their cells were all experiences of mine at the old “Spanish Jail” section of San Quentin and which I dutifully shared with the Stanford Prison Experiment braintrust months before the experiment started. To allege that all these carefully tested, psychologically solid, upper-middle-class Caucasian “guards” dreamed this up on their own is absurd. How can Zimbardo and, by proxy, Maverick Entertainment express horror at the behavior of the “guards” when they were merely doing what Zimbardo and others, myself included, encouraged them to do at the outset or frankly established as ground rules?

(worth noting that Zimbardo believes Prescott used a ghost writer. Not sure if that changes anything)

Zimbardo, hardly an impartial observer, acted as superintendent of the guards, and gave strong queues as to what behaviour was acceptable and even desired. University of Queensland’s Alex Haslan reviewed audio recordings of the experiment and in a 2018 study stated:

The totality of evidence indicates that far from slipping naturally into their assigned roles, some Guards actively resisted and were consequently subjected to intense efforts from the Experimenters to persuade them to conform to group norms for the purpose of achieving a shared and admirable group goal.

Haslan continues to explain how even with such a small sample size, there were dissenters among the subjects:

it is clear that many participants did not conform to role. Many Prisoners continued to resist authority until the end of the study (Le Texier, 2018; Reicher & Haslam, 2006). Likewise, many Guards refused to assert their authority.

One of the subjects who happily engaged in the role-play was Dave Eshelman. He had planned his own behaviour from the beginning:

What came over me was not an accident. It was planned. I set out with a definite plan in mind, to try to force the action, force something to happen, so that the researchers would have something to work with. After all, what could they possibly learn from guys sitting around like it was a country club? So I consciously created this persona. I was in all kinds of drama productions in high school and college. It was something I was very familiar with: to take on another personality before you step out on the stage. I was kind of running my own experiment in there, by saying, “How far can I push these things and how much abuse will these people take before they say, ‘knock it off?’” But the other guards didn’t stop me. They seemed to join in. They were taking my lead. Not a single guard said, “I don’t think we should do this.”

Roleplaying also occurred on the other side of the bars. Douglas Korpi left on the second day of the experiment, screaming ‘I just can’t take it anymore!’ on camera. His ‘breakdown’ was considered a ‘defining moment’ of the study. Douglas Korpi claims it was faked, and done in order to return to studying, something which was not permitted in his cell. Zimbardo claimed prisoners need only say ‘I quit the experiment’ to leave, but transcripts of a taped conversion show Zimbardo saying ‘There are only two conditions under which you can leave, medical help or psychiatric’.

There are some other peculiarities to the experiment that suggest demand characteristics (i.e. wanting to prove what your experimenter believes) and role playing were behind the weirdness, rather not a genuine ‘loss of reality’. A 1975 critique of the experiment by Ali Banuazizi and Siamak Movahedi explains:

The fact that on the occasion of a visit by a Catholic priest some of the prisoners referred to themselves by their prison identification numbers, rather than their Christian names, has been offered by the authors as further evidence for their reality transformation hypothesis. Since to our knowledge real prisoners rarely, if ever, introduce themselves to outsiders, particularly a sympathetic visitor, by their official prison numbers, we can only interpret the behavior of their subjects as a case of overzealous role players attempting to be more Catholic than the Pope

Banuazizi and Movahedi, as part of their critique, ran their own experiment, restating the ad from the original experiment to 150 subjects, and asking them what they think the experiment might be trying to prove. 81% were able to ‘articulate, quite clearly, the intent of the experiment, that is, the general hypothesis’.

Some example responses:

“Experimenter is trying to prove the contention that he has about jails. He believes that people are pushed about, put down, and humiliated in jails and other correctional institutions.”

“Testing endurance-to see how far you go before fighting back, I think they are trying to find out what causes prison riots.”

“He is trying to find out if anybody would fit into either of the two roles. That is, figuring that everyone is equal, a person selected as a guard will behave, act, and become like a guard; if a person is selected to be a prisoner, he will act, behave, and become like a prisoner.”

If there’s anything I want to communicate in this post, it’s that people aren’t stupid. And to the extent to which they are stupid, they’re certainly not as stupid as these kinds of psychological experiments would lead you to believe. If 81% of respondents to this survey knew exactly what Zimbardo was looking for, it’s no surprise that the subjects of the original experiment knew how to play the part.

You might think: well it’s too late to see whether this experiment replicates, because no ethics committee would permit it. Luckily, we don’t have to. In 2001, Haslan, along with psychologist Stephen Reicher, worked with the documentaries unit of the BBC to partially recreate the original experiment over eight days. The ‘BBC Prison Study’ abstained from the nudging towards oppression that Zimbardo gave his guards, and observed a reversed outcome: guards who were ‘wary of assuming and exerting their authority’, and prisoners who soon banded together and demanded better food and the ability to smoke; demands which one guard responded to by actually offering a cigarette.

Given the inability to replicate the original experiment with stricter controls, it’s almost as if a small sample size, motivated reasoning, unchecked demand characteristics, and outright lies make for a crappy experiment.

Yet the Stanford Prison Experiment is still heralded as a breakthrough in psychology research, showing people how malleable human identity can be, and how after 24 hours in a new environment anybody can organically turn violent and oppressive. We all know humans can, with enough time, go bad, but you’re gonna need a whole lot more time than was allotted for this experiment.

Psychology textbooks are in no hurry to cast doubt on the experiment’s conclusions, with Richard Griggs’ 2014 Article ‘Coverage of the Stanford Prison Experiment in Introductory Psychology Textbooks’ finding that of the 11 texts dealing with the experiment, 5 contained no criticism at all. The majority of the criticism was around the ethics of the experiment rather than the validity of its conclusion, and only two texts mentioned the BBC Prison Study.

If I didn’t know any better I’d say that textbook authors haven’t looked into criticisms of the experiment because they’re perfectly comfortable with its blank-slate conclusion, and that the blank-slate hypothesis is, to many, far preferable to the idea that the human mind is not very malleable, and that a person’s disposition is a far better predictor for their actions than their immediate circumstances. But I don’t know any better so I’ll leave it at that.

I hope you enjoyed reading this as much as I enjoyed writing it, and I hope that I’ve inspired others to do some digging when they suspect something they learnt in highschool might be bullshit.




Could Be Wrong

Less and less certain of my opinions with every passing day