As the brain is doing all this processing and threat-preparing, it is also zapping an area on its side, the anterior temporal lobe, and telling it to serve up all the stereotypes you might have associated with that person’s group. That means if you see a transgender person, your brain might play you Tootsie, Caitlyn Jenner, and size 13 stilettos, in a kind of very primitive, insidious Netflix queue. We tend to remember people by whatever it is that makes them unusual—a dwarf doctor is memorable because he is a dwarf, not a doctor—and we assume that people will be just like other people who have their same unique trait.131

In a 2002 article,132 the Princeton psychologist Susan Fiske described most people’s feelings toward outside groups, like the disabled or elderly, as one of “cool neglect.” Most people rarely express open hostility toward outsiders; they just don’t like or respect them as much as their own group. In fact, most people who are biased against other groups tend to perform worse on cognitive tests after being exposed to members of other races: they’re focusing all their energy on tamping down their prejudice so they can seem fair-minded.133 Even if our brains are swirling with bias, to the outside world, we try to look impartial.

Amodio thinks these hypersensitive neural responses might have served a purpose at some point in humans’ ancestral past. Today, though, this instinct sets us up to avoid or alienate people who don’t look or act like us.

Our distrust of outsiders might even explain the surprising rise of Donald Trump, who frequently targets minorities and the “other” on Twitter and in his policies. Michele Gelfand, the psychologist who studies tightness and looseness, has suggested that Trump’s campaign-trail reminders of “threats” such as Mexican immigrants and Syrian refugees sparked voters’ desire for cultural tightness.

Recall that tightness is how much we stick to norms. It means a return to law and order, another Trump standby. In Gelfand’s research, concern about various threats predicted both people’s psychological tightness and their support for Trump. Normative tightness, Gelfand found, predicted voting for Trump beyond .001 percent of a statistical doubt. “Perceptions of threat tighten societies, leading to social coordination at best, and intolerance at worst,” she and her colleagues wrote in 2016.134

Multiple studies and surveys have now shown that it was a fear of losing status to other groups—like immigrants and people of color—that motivated many white Americans’ support for Trump.135 As I wrote for The Atlantic in 2018,136 Trump supporters were more likely than Clinton voters to feel that the “American way of life is threatened,” which is about as clear a signal as seizing a sociologist by the lapels and screaming, “I’m feeling status threat!”