Paranoia and the brain

Gregory Nemec

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From the great fire of ancient Rome, to the Black Death of the Middle Ages, to the COVID-19 pandemic in our own day, humans have often responded to devastating shifts in the world around them by looking for someone to blame. 

While anyone may wonder occasionally if there’s someone “out to get me,” some people are more prone to conspiracy fears and paranoia than others. Associate Professor of Psychiatry Philip Corlett, with a team from Yale and other universities, set out to understand why. They wanted to test the idea that paranoia stems not simply from errors in how we assess social situations, but also from how the brain itself forms and updates beliefs about the world. The study was published in eLife.

The team had participants play a card game. Some players had been diagnosed with psychiatric symptoms; others had not. (The players did not compete against each other.) What none of them knew was that, partway through, the researchers changed the best option for success. Those in the control group were slow to assume that the best choice had changed. But those with paranoia expected still more volatility, and they played more erratically.

Then the uncertainty increased: halfway through, the researchers again manipulated the chances of winning. After that, even the control group played more chaotically.

In another experiment, rats trained to complete a task were rewarded with sugar. Some received methamphetamine; it causes paranoia in humans. When the researchers changed the site of the reward, the drugged rats behaved like paranoid humans: they expected the reward site to change often.

By creating experiments that did not require interacting with others, the researchers were looking beyond social situations to examine fundamental learning mechanisms. Says Corlett, “The way we studied paranoia is new.”