Newly analysed recording challenges Zimbardo’s account of his infamous prison experiment

What leads some people to tyrannise others, as when guards abuse their prisoners? The US psychologist Philip Zimbardo would say it's the corrupting power of the situation. Infamously, in the summer of 1971, his prison simulation study had to be abandoned when some of the volunteers playing the role of guards began mistreating the volunteers acting as prisoners.

The shock value of the aborted study derives in large part from the idea that the mock prison took on a life of its own; that otherwise "ordinary" folk began behaving in abhorrent ways simply because they'd been assigned a role with particular connotations. As Zimbardo put it, the guards' brutality occurred "as a natural consequence of being in the uniform of a 'guard'".

But not everyone buys this account. Critics of the Stanford Prison Experiment have long claimed that Zimbardo and his colleagues did not merely observe, but actively participated in the events that unfolded.

Now a team led by Alex Haslam at the University of Queensland has analysed a recently released recording of a conversation between one of the volunteer guards and Zimbardo's collaborator David Jaffe, who acted as prison warden for the study. The findings of their analysis, released as a pre-print at PsyArXiv, suggest that one of psychology's most famous studies was not so much an experiment but more a form of theatre. "We can no longer airbrush out the role of the experimenters in producing brutality," write Haslam et al.

The conversation, available for anyone to listen to online (starts from 8.38), is 18-minutes long and features Jaffe attempting to persuade the "guard" John Mark to behave more like a stereotypical tough guard, a role he is clearly reluctant to take on.

Haslam and his colleagues analysed the interaction specifically looking for evidence of whether Jaffe engaged in "identity leadership", which is characterised by the leader creating a shared sense of identity (a "them" and "us" mentality) and painting the required behavior of the in-group (the "us") as worthy and virtuous and beneficial to the in-group.

The researchers found multiple examples of Jaffe engaging in precisely these kind of leadership tactics – for instance, he uses the collective "we" 57 times in the conversation (or once every 30 words); he argues that the entire endeavor will fall apart unless Mark and the other volunteer guards behave as required; and he portrays this shared endeavour as worthy, as a way to increase the chance of real-life prison reform.

Indisputably, Jaffe does not sit back and allow Mark to choose freely how to behave in his assigned role of guard: "… [W]e really want to get you active and involved because the Guards have to know that every Guard is going to be what we call a tough Guard," he tells Mark.

The newly analysed recording, together with earlier video footage of Zimbardo acting as "prison superintendent" and briefing the guards on what was expected of them, contradict the way that Zimbardo has portrayed the experiment, as if the unsettling events unfolded by themselves. It seems more accurate to view the Stanford Prison Experiment as a compelling example of semi-scripted improvised theatre rather than as objective scientific research. Hopefully such an interpretation will find its way through to our introductory textbooks, many of which present only Zimbardo's account of what happened.

But still, it remains the case that some of the volunteers assigned to the role of guards went way beyond the script, engaging in such cruel behaviour as forcing the "prisoners" to clean out toilets with their hands. How satisfactory is the social identity account that Haslam and his co-authors put forward as an explanation for why some of the guards resisted engaging in tyranny, while others willingly went way beyond Zimbardo and his colleagues' expectations, not just acting tough, but engaging in depravity?

Haslam and his colleagues admit that to claim, on the basis of the new evidence, that identity leadership was responsible for the guards' brutality "would be to go too far".

Even while recognising the important influence of Zimbardo and his colleagues on the events that took place at Stanford (and why it was so persuasive), many will remain appalled by the sadism on display, and crave a deeper explanation for the darkness that resides within seemingly ordinary people. As science writer and sceptic Michael Shermer wrote on Twitter in response to these new findings and wider criticisms of the Stanford Prison Experiment, "The fact remains that the potential for evil lies in our nature given the right circumstances."

Further reading

—Rethinking the 'nature' of brutality: Uncovering the role of identity leadership in the Stanford Prison Experiment [this study is a pre-print meaning that it has not yet been subjected to formal peer review and the final published version may differ from the version reported on here]

•  The Lifespan of a Lie
  The most famous psychology study of all time was a sham. Why can't we escape the Stanford Prison Experiment?
• Time to change the story
  New evidence from the Zimbardo archives challenges everything you have taught (or been taught) about the Stanford Prison Experiment, argue Stephen Reicher, S. Alexander Haslam and Jay Van Bavel.
• Philip Zimbardo defends the Stanford Prison Experiment, his most famous work
• Formal response from Zimbardo on the Stanford Prison Experiment website

About the author

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest