For nearly 50 years now, the Stanford Prison Experiment has been held up as proof of how combustible personal interactions can be, how the bonds of humanity can disappear in a flash.

The design of the 1971 study was quite simple: randomly assign nine “normal” male college students to be prison guards, dress them in uniforms, give them billy clubs and authority over a pretend prison located in a university basement where nine other “normal” male college students were brought in as inmates.

The purpose of the experiment, conducted by a recently tenured young Stanford psychology professor, Philip Zimbardo, was to examine how authority was wielded within prison walls. In short order, however, it exploded into cruelty and sadism. Guards spewed verbal abuse, manhandling the prisoners and demanding that they go to the bathroom in buckets. Some student/prisoners screamed to be allowed to walk out the door.

Noam Cohen Ideas Contributor Twitter Noam Cohen is a journalist and author of The Know-It-Alls: The Rise of Silicon Valley as a Political Powerhouse and Social Wrecking Ball, which uses the history of computer science and Stanford University to understand the libertarian ideas promoted by tech leaders. While working for The New York Times, Cohen wrote some of the earliest articles about Wikipedia, bitcoin, Wikileaks, and Twitter. He lives with his family in Brooklyn.

Zimbardo had intended for the experiment to run two weeks, but by the sixth day he had seen enough. From the chaos, a vital lesson emerged for Zimbardo: “Ordinary students can do horrible things.”

This insight found fertile soil in the early 1970s. The Attica prison uprising and its violent suppression later that year seemed to bear out this shocking, disturbing, compelling conclusion about how prisons themselves encourage abuse and people quickly conform to what institutions expect of them. Zimbardo was invited to testify before Congress about prison reform. There was a documentary that relied on six hours of filmed recordings of the experiment (with another 48 hours of audio recordings to supplement it).

When the Abu Ghraib prisoner abuses emerged decades later, Zimbardo was again called by Congress to explain the sadistic behavior. In 2015, a feature movie about the experiment was released, with posters showing sunglass-wearing guards throwing inmates, dressed in hospital gowns and nylon sleeping caps, up against the wall, forearms pressed against their necks. Who knows what evil lurks in the hearts of men? Zimbardo knows.

Except that as a work of science, the Stanford Prison Experiment has now been judged to be fatally flawed. A paper published this month in American Psychologist, the peer-reviewed journal of the American Psychological Association, represents a repudiation of the experiment after years of pointed questions from other researchers. The paper, “Debunking the Stanford Prison Experiment,” concludes by describing the research as “an incredibly flawed study that should have died an early death.”

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The paper’s author, Thibault Le Texier, a French researcher who spent years analyzing the archives documenting the prison experiment and interviewing the participants, documents how Zimbardo and his assistants ordered the guards to become cruel, and, moreover, that guards and prisoners alike knew what Zimbardo was trying to prove and were eager to help.

In other words, the sadism of the guards and the submissiveness of the prisoners in the experiment didn’t reveal the hidden darkness of the human soul, so much as the willingness of college students to please a professor.

The de facto endorsement of Le Texier’s allegations by America’s psychologists—remember, the article was peer-reviewed—would seem like a towering example of truth triumphing over falsehood. In taking down the Stanford Prison Experiment, Le Texier wasn’t tangling with any old study, but perhaps the most famous social science project. The prison experiment has been a staple of psychology textbooks, and Zimbardo himself is a past president of the American Psychological Association. But as Le Texier is quick to concede in an interview from Paris, his debunking of the experiment may be a case of closing the barn door after the horse has run off.

The Stanford Prison Experiment has burrowed its way into the culture, inspiring an epiphany-industrial complex that deploys social science research in support of facile claims about human nature, public policy, and interpersonal relationships. There are TED talks and Freakonomics case studies, online personality tests, influential books, and articles that advise which tipping points to avoid or seek out, how to feel better by doing power poses, and how to be happy.