The Stanford Prison Experiment — one of the most infamous psychological spectacles of all time — was purported to show how circumstances can bring out the worst in all of us. In the experiment, Stanford professor Philip Zimbardo assigned paid volunteers to be either inmates or guards in a simulated prison in the basement of the school‘s psychology building. It was supposed to be a naturalistic exercise on what happens when some people are given power and others are denied it.

Critically, Zimbardo stated in a 1971 document describing the experiment that “the guards were given no specific instruction or training on how to be guards.”

“Instead,” he said, “they were free, within limits, to do whatever they thought was necessary to maintain law and order in the prison and to command the respect of the prisoner.”

This week, the story of the experiment changed considerably. In a thoroughly reported exposé on Medium, journalist Ben Blum finds compelling evidence that the guards in this experiment were not left to act on their own desires. Audio recording and interviews with those involved reveal the guards were coached into being mean or considered the experiment to be an “improv exercise.” Here is one of those recordings, via the Stanford archive. It’s pretty damning. You can hear David Jaffe, one of Zimbardo’s students who acted as the prison “warden,” chastising a guard for not being severe enough.

(The quality of the audio is not great. It is, after all, a nearly 50-year-old tape cassette recording. You can read the transcript below. Emphasis added.)

JAFFE: Generally, you’ve been kind of in the background. Part of that is my fault because I’ve gone along with when you wanted to sit outside while they were doing count. Or that sort of thing. But 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.” And so far ... GUARD: I’m not too tough. JAFFE: Yeah. Well, you have to try to get it in you. GUARD: Well, I don’t know about that. JAFFE: See, the thing is, what I mean by tough is you have to be firm, and you have to be in the action, and that sort of thing. It’s really important for the workings of the experiment because whether or not we can make this thing seem like a prison, which is the aim of the thing depends largely on the guards’ behavior.

These revelations significantly change the conclusions of the experiment, if you can even call it that anymore. (Many now think of it as much more of a dramatic demonstration than a serious scientific endeavor. And recall: It was even terminated before its set end date.) That some of the guards were coached cuts against the implication that being placed in a position of power leads to cruelty. If anything, it shows how an authority figure can persuade another into conformity.

“The bottom line is that conformity isn’t natural, blind or inevitable,” NYU social psychologist Jay Van Bavel tweeted in light of these revelations. “Zimbardo was not only deeply wrong about this — but his public comments misled millions of people into accepting this false narrative about the Stanford Prison Experiment.”

Further reading: the prison experiment