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There's a Distinct Brain Function Behind Prejudice

New neural research could help us design better anti-prejudice interventions.

It's unclear if he's guiding or merely reflecting the views of his supporters, but President Donald Trump clearly conceives of undocumented immigrants as less than fully human. Just last week, in defending his since-rescinded policy of separating parents and children, he declared that such people would "infest" the United States—a term usually used to describe insects or vermin.

Psychologists have traditionally believed this mindset, which has been linked to horrible actions throughout history, was rooted in animosity. But new research provides evidence that dislike and dehumanization activate distinct patterns of brain activity.

"When people are dehumanizing others, they are mobilizing different brain regions than when they are registering their dislike," Emile Bruneau, director of the Peace and Conflict Neuroscience Lab at the University of Pennsylvania's Annenberg School for Communication, said in announcing the findings. He believes they could help us design more effective interventions to reduce prejudice.

In the Journal of Experimental Psychology: General, Bruneau and his colleagues describe a study featuring 24 adults from the greater Boston area. While the brains were scanned, they completed a survey in which they expressed their views about a diverse set of 10 groups, including Europeans, Muslims, the homeless, surgeons, rats, and robots.

They rated each on a series of scales, including how warm they felt toward the group, and where they would place it on the famous "ascent of man" scale depicting various stages of evolution. Those responses measured liking/disliking and dehumanization, respectively.

Essentially, the researchers found different parts of the brain were activated when making those two judgments. This suggests one can dismiss a group as less than fully human—a belief that can justify actions like separating parents and children—even if you don't feel strong animus toward it.

The researchers were particularly struck by the response of the left interior frontal cortex. This brain region "showed greater activity in response to animals and low-status human groups vs. high-status human groups," they report.

This neural mechanism "may underlie a shared moral disregard toward both animals and low-status groups, distinguishing them both from 'fully evolved' humans."

The findings, if confirmed, could provide valuable information to educators and social justice advocates who are attempting to fight prejudice.

"If prejudice and dehumanization are cognitively distinct processes," the researchers write, "it is possible that making a group seem more likable" is an ineffective way of convincing people they are just as human as you are. Increasing likability may not override "a tendency to consciously perceive them as primitive or brutish."

They argue that "promoting a sense of the target out-group as civilized, sophisticated, and capable" might be more effective in that it directly challenges one's instinctual tendency to view them as less than fully human.

So the propensity to dehumanize appears to be part of our neural make-up, ripe for exploitation by unscrupulous politicians. But understanding its neural roots may help us counter it.