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The Stanford Prison Experiment part 2: an alternative explanation (involving rotten apples)

LevineRotten Apples

(Image from Alan Levine at

This is the second of three posts on the Stanford Prison Experiment: the myth of what happened (last post), an alternative explanation for what happened (this post), and how that relates to the abuses at Abu Ghraib (next post).
The oversimplified version of the SPE is that the guards all became abusive, irrespective of their values and personalities, because they fell into the role required of them in the prison situation. Zimbardo’s full account of the study in The Lucifer Effect (2007) shows it was much more complicated than that, and he discusses thoughtfully and at length the various processes involved. As usual, this shows the value of going back to original accounts or papers, rather than relying on the text-book versions. I’ve discussed in the previous post how Zimbardo’s account shows considerable ‘personality-related’ variation in behaviour amongst both prisoners and guards, and questioned the extent to which situation/role governed everyone’s behaviour (though Zimbardo points out quite convincingly how he himself was overcome by the expectations of the ‘prison governor’ role).

The kind of thing that happened in the SPE does happen in other total institutions* (schools, children’s homes, care homes: see examples in the previous post), so the ‘SPE effect’ is pretty robust – but not all these total institutions have potentially dangerous inmates and a punitive (or at least corrective) ethos like a prison, so it can’t be simply the ‘prison guard role’ which is causing the effect.
My explanation is rather simple: individuals with a propensity for bullying and the ‘rotten apple’ effect, coming together in a total institution environment with lax controls on worker behaviour.

Zimbardo’s account distinguishes clearly between the ‘tough guards’ and the ‘good guards’, and even discusses a power struggle between them, which the tough guards win. One individual stands out: a guard named by Zimbardo in the book as Hellman (not his real name), who the other guards nicknamed ‘John Wayne’. In the available videos of the SPE which you may have seen he is a tall guard with straight fair hair who usually appears as taking a lead role in taunting the prisoners, and The Lucifer Effect emphasises his dominance and enthusiasm for mistreating the prisoners (which Hellman presents as his own ‘experiment’ to see how far he could go before someone stopped him: Zimbardo, 2007, p194).
Zimbardo commented on him, years later: “He was creative in his evil. He would think up very ingenious ways to degrade, to demean the prisoners.” BBC2 (2002)
Just after the end of the experiment, one of the prisoners talking to Hellman about how he might have behaved himself as a guard says: “I don’t think, I don’t believe, I would have been as inventive as you. I don’t think l would have applied as much imagination to what I was doing. Do you understand? […] I think I would have been a guard, I don’t think it would have been such a masterpiece!.” Zimbardo 2007, p193
I also remember Zimbardo reporting a conversation between one of the other guards and Hellman: “I know we have to do this stuff, Dave, but you don’t have to be so damn good at it.” I’m ashamed to say I can’t find the source for this now: if you know it, please let me know.

So, a personality difference, with one person seemingly more inclined to be abusive than others. But several other guards followed his lead, and no other guard, even ones that both Zimbardo and the prisoners regarded as ‘good guys’, effectively stopped the abuse. This is where the rotten apple effect comes in.

Rotten apples

Whenever some example of institutional abuse or corruption emerges, some senior spokesperson will blithely say ‘of course, there are always a few rotten apples, but….’ to reassure the public that there’s no fundamental problem. Such people are using a metaphor they don’t understand (don’t you hate people like that?), are actually confirming (if they understood what they were saying) that there is a real systemic problem, and worst of all DON’T KNOW ABOUT STORING FRUIT. The point about a rotten apple is that it quickly makes all the other apples in the barrel rotten. If it’s not removed at the first sign of decay, the whole lot can be lost. And that’s what rotten apples do: they’re not isolated instances – they’re centres of systemic corruption, once they’re allowed to get away with their rottenness. That seems to be what happened in the SPE: a ‘creatively evil’ person, running their own ‘experiments’, and lax management (Zimbardo), who allowed that kind of thing to take hold. Zimbardo is well aware of that in retrospect, and in The Lucifer Effect he staunchly owns up to his responsibility. Zimbardo does understand the metaphor, but he turns it around by suggesting that the situation was a ‘rotten barrel’ which infected the apples, not the other way around. There is some truth in that, and it may be a characteristic of total institutions (especially those with lax management) to provide ideal conditions for the infection to spread unopposed, but the influence of someone like guard Hellman is an important starting point. There seems to have been a similar influence at Abu Ghraib, which I’ll describe in the next post.

* The term ‘total institution’ comes from Erving Goffman’s 1961 book Asylums: well worth reading as background to all this stuff. (Everything Goffman wrote is well worth reading.)

A total institution may be defined as a place of residence and work where a large number of like-situated individuals, cut off from the wider society for an appreciable period of time, together live an enclosed, formally administered round of life. Goffman, 1961, 1991: p11 in 1991 Penguin edition

An ‘appreciable period of time’ doesn’t have to be continuous, I think, so day schools can fit here, though boarding schools do fit better.

The standard ref for the Stanford Prison Experiment is:
C Haney, C Banks, P Zimbardo (1973) Interpersonal dynamics in a simulated prison – International Journal of Criminology and Penology, 1, 69-97 (note this isn’t a psychological journal), but you probably won’t be able to get hold of that.

BBC2 (2002) The Stanford Prison Experiment

Goffman, Erving (1991, 1961) Asylums: essays on the social situation of mental patients and other inmates London: Penguin Books

Zimbardo, Philip (2007, 2009) The Lucifer Effect London: Rider

There are very extensive and informative websites about the SPE at and The Lucifer Effect at (but that’s not a substitute for reading the book).


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