The Disease Theory of Xenophobia

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Recent incidents like the San Bernardino shootings and the Cologne sexual assaults have certainly contributed to these anxieties. But on a broader scale, the human desire to keep out “the other” might be partly explained by a vestigial psychological quirk that was once meant to help protect us from infection. The mechanism, called the behavioral immune system, tells us to avoid things that are unfamiliar because they might harbor harmful pathogens.

The phenomenon helps explain a whole host of subconscious reactions, like prejudice against people with facial birthmarks, an attraction to symmetrical faces, and, yes, strong anti-immigration views. In some cases, the behavioral immune system might have a point: The sight of pus and blood makes some people queasy because touching another person’s infected wound without gloves is dangerous. But the behavioral immune system, like an allergy, is so sensitive that it’s often wrong. It sometimes hurts us more than it helps.

In a new review paper published this week in Advances in Experimental Social Psychology, the psychologists Damian R. Murray, from Tulane University, and Mark Schaller, from the University of British Columbia, explain where these behavioral defenses against infection came from–and how they can deceive.

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In centuries past, then, it may have been healthy to tread carefully around foreigners. Not only might outsiders carry dangerous germs, they also might not be familiar with the kinds of local customs–food-preparation laws or sexual practices–that conferred some measure of protection against communicable diseases.

The trouble is, with modern medicine most people no longer have to worry when they come into casual contact with someone from a different country. (Some researchers believe, in fact, that our lives are now too sanitary.) Still, our hypervigilant behavioral immune systems scan the landscape for foes, be they real or fake, to keep away from our delicate bodies.

A mere encounter with someone or something unfamiliar might set off our sense of disgust, an especially hair-trigger response. Here, our behavioral immune systems are helped out by the more primitive regions of the brain. According to New York University psychologist David M. Amodio, two things happen when we’re under threat and encounter a person from outside our group. First, the amygdala reacts by freezing our behavior–we stop, we stare–and preparing the body for fight or flight. And second, if the person is disliked, they might elicit a response from the insula, the brain region that generates a sense of deep-in-the-gut revulsion.

This impulse doesn’t always work in our favor. Some studies suggest the reason why pregnant women develop morning sickness in their first trimester, when their immunity is lower, is because they are more wary of infection and therefore more revolted by everything. {snip}

Pregnant women in their first trimester, as it turns out, also exhibit more ethnocentric and xenophobic attitudes than those further along in their pregnancies. That’s a trend researchers have found across studies and across borders: The more vulnerable we feel to disease, the more likely we are to want to build a proverbial wall (and make Mexico pay for it!). One early study by Schaller and others found that people who are more worried about getting sick are more likely to associate foreign groups with danger and have more hostile attitudes toward foreign-immigrant groups. In another experiment, Canadians who were shown images of infectious diseases were less likely to support immigrants from exotic-seeming countries, such as Mongolia, than were those who saw images of other types of threats, like car accidents.

The findings have held up across cultures. {snip}

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But there is some evidence that the behavioral immune system amps up certain brands of conservatism. One meta-analysis of 24 studies found that the strength of one’s behavioral immune system, as measured by things like a fear of contamination or sensitivity to disgust, is positively correlated with social conservatism–including ethnocentrism. {snip}

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