What the textbooks don’t tell you – one of psychology’s most famous experiments was seriously flawed

Conducted in 1971, the Stanford Prison Experiment (SPE) has acquired a mythical status and provided the inspiration for at least two feature-length films: Das Experiment and The Experiment. You'll recall that several university students allocated to the role of jailor turned brutal and the study had to be aborted prematurely. Philip Zimbardo, the experiment's lead investigator, says the lesson from the research is that in certain situations, good people readily turn bad. "If you put good apples into a bad situation, you'll get bad apples," he has written.

The SPE was criticised back in the 70s, but that criticism has noticeably escalated and widened in recent years. New details to emerge show that Zimbardo played a key role in encouraging his "guards" to behave in tyrannical fashion. Critics have pointed out that only one third of guards behaved sadistically (this argues against the overwhelming power of the situation). Question marks have also been raised about the self-selection of particular personality types into the study. Moreover, in 2002, the social psychologists Steve Reicher and Alex Haslam conducted the BBC Prison Study to test the conventional interpretation of the SPE. The researchers deliberately avoided directing their participants as Zimbardo had his, and this time it was the prisoners who initially formed a strong group identity and overthrew the guards.

Given that the SPE has been used to explain modern-day atrocities, such as at Abu Ghraib, and given that nearly two million students are enrolled in introductory psychology courses in the US, Richard Griggs, professor emeritus at the University of Florida, says "it is especially important that coverage of it in our texts be accurate."

So, have the important criticisms and reinterpretations of the SPE been documented by key introductory psychology textbooks? Griggs analysed the content of 13 leading US introductory psychology textbooks, all of which have been revised in recent years, including:  Discovering Psychology (Cacioppo and Freberg, 2012); Psychological Science (Gazzaniga et al, 2012); and Psychology (Schacter et al, 2011).

Of the 13 analysed texts, 11 dealt with the Stanford Prison Experiment, providing between one to seven paragraphs of coverage. Nine included photographic support for the coverage. Five provided no criticism of the SPE at all. The other six provided only cursory criticism, mostly focused on the questionable ethics of the study. Only two texts mentioned the BBC Prison Study. Only one text provided a formal scholarly reference to a critique of the SPE.

Why do the principal psychology introductory textbooks, at least in the US, largely ignore the wide range of important criticisms of the SPE? Griggs didn't approach the authors of the texts so he can't know for sure. He thinks it unlikely that ignorance is the answer. Perhaps the authors are persuaded by Zimbardo's answers to his critics, says Griggs, but even so, the criticisms should be mentioned and referenced. Another possibility is that textbook authors are under pressure to shorten their texts, but surely they are also under pressure to keep them up-to-date.

It would be interesting to compare coverage of the SPE in European introductory texts. Certainly there are contemporary books by British psychologists, such as Psychology: The Science of Mind and Behaviour, Social Psychology: Revisiting The Classic Studies and The Rough Guide to Psychology that do provide more in-depth critical coverage of the SPE.

Griggs' advice for textbook authors is to position coverage of the SPE in the research methods chapter (instead of under social psychology), and to use the experiment's flaws as a way to introduce students to key issues such as ecological validity, ethics, demand characteristics and subsequent conflicting results. "In sum," he writes, "the SPE and its criticisms comprise a solid thread to weave numerous research concepts together into a good 'story' that would not only enhance student learning but also lead students to engage in critical thinking about the research process and all of the possible pitfalls along the way."

Further reading

Griggs, R. (2014). Coverage of the Stanford Prison Experiment in Introductory Psychology Textbooks Teaching of Psychology, 41 (3), 195-203 DOI: 10.1177/0098628314537968