The Stanford Prison Experiment: Recent evidence questions whether we have been given the right story (Photo source:

Following the digitization of material from the official Stanford Prison Experiment (SPE) archive, in recent weeks there has been a flurry of activity about Zimbardo’s classic study. In particular, this has resulted from evidence presented by the French researcher Thibault Le Texier in his book Histoire d’un Mensonge [Story of a Lie] and the American journalist Ben Blum. Their independent forensic investigations cast serious doubt on Zimbardo's official account of his study.

Amongst other things, but particularly important for us, this new evidence serves to question Zimbardo’s claim that the brutality displayed by Guards in the SPE was a "natural" consequence of their being assigned this role. Instead, it is clear that the Experimenters went to great lengths to encourage the Guards to behave in particular ways. Critically, this leadership role has not previously been discussed in formal accounts of the study, and it is also absent from Zimbardo's own theorizing.

Yet, at the same time that it casts doubt on Zimbardo's analysis, this new evidence accords closely with our own theoretical analysis which suggests that identity leadership is central to the emergence of tyranny. More particularly, it speaks to our claim that in order to encourage others to engage in acts of oppression, leaders need (1) to create a sense of shared identity between themselves and potential followers, (2) to persuade followers that the oppression of others is necessary for the achievement of ingroup goals, and (3) to present oppression as fundamentally noble and virtuous.

There is an abundance of evidence in the archive that speaks to these various processes and we are grateful to both Le Texier and Blum for drawing this to our attention. One interaction is especially illuminating, however. This took the form of a 18-minute meeting between Zimbardo’s prison Warden, David Jaffe, and a reluctant Guard, John Mark.

This is well worth listening to, and we recommend that you do this. The recording of the meeting can be accessed through the archive here (start at 8.38).

On the one hand, contrary to Zimbardo’s (2004) claims that participants’ prior understanding of their assigned roles was “the sole source of guidance”, it is clear from the recording that Guards were cajoled into behaving in particular ways. Indeed, the meeting starts with the Warden saying “we 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”.

On the other hand, the meeting provides an abundance of evidence of identity leadership in action. First, the Warden repeatedly uses collective pronouns (“we”) to create a sense that the Experimenters and Guards are a team working towards shared goals.  Second, the Warden tries to persuade the Guard that toughness is necessary for the achievement of those goals. Toughness, he says, is "really important for the workings of the Experiment”. And, third, he presents those goals as fundamentally worthy. Why? Because the research is going to generate “some very serious recommendations for [prison] reform”.

Working closely with Jay Van Bavel from New York University, we have written up a formal analysis of these various dynamics for publication. A pre-print of our paper is available on PsyARXiv. At the same time we have also written some more accessible articles for The Psychologist and In-Mind.

Zimbardo has responded to some of our and others’ criticism on his own website and in a lively interview with Brian Resnick for Vox. Although he argues that “none of these criticisms present any substantial evidence that alters the SPE’s main conclusion” it is notable that he fails to engage with any of the substantive analytical points that we make or with our broader theoretical argument about the importance of identity leadership for outcomes observed in the SPE (and for the emergence of tyranny in the world at large).

Our sense, however, is that while Zimbardo's strategy of ignoring our theoretical arguments has worked in the past, this debate — which it has always been our objective to progress — is now impossible to avoid.