In 1971, Philip Zimbardo conducted the Stanford Prison Experiment, during which students were divided into “guards” and “inmates,” and the guards soon began to treat the inmates horribly. But according to BPS Research Digest (hat tip to William Rinehart):
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.
But even if all the criticisms of the Stanford Prison Experiment are true, it’s still the case that “one third of guards behaved sadistically” at Zimbardo “encouragement.” That still says something very important about the human capacity to mistreat other people.