Disgust, Prejudice, and Stereotypes: Pathogen Protection Gone Awry

Can our immune system lead us astray?

Every day, our bodies fight off disease. But it’s costly to launch a full-out immune response, and over time, we’ve also evolved mechanisms for avoiding dangerous substances to begin with. The behavioral immune system (a term coined by Mark Schaller) is one such mechanism, a psychological armory against environmental pathogens – but it may affect us more deeply than we are aware.

What is the behavioral immune system?

In this system, psychological mechanisms detect environmental cues that might indicate the presence of infectious pathogens in our immediate vicinity. They then trigger emotional and cognitive responses, such as disgust and avoidance, that will help us alter our behavior to avoid these elements that have been labeled potentially harmful. Sounds smart, right? Not only can we physically fight off disease, but our brain helps us avoid it behaviorally in the first place. But there’s a catch.

When the system goes wrong: overly-general aversion could contribute to stereotypes and prejudice

The behavioral immune system can only differentiate very general, superficial environmental cues; it doesn’t have the specificity that our actual immune system is able to display once pathogens enter our actual bodies. As a result, it can end up reacting to things that don’t actually pose any threat – and these things include people. In short, the behavioral immune system might alter our perception of the world and act as a subtle (or at times, not so subtle) influence on the decisions we make, not always in a good way.

Some recent findings are especially provoking.

Avoiding the disabled, the obese, and the elderly

Studies have shown that the perceived threat of infection predicts strongly prejudiced behavior toward people who have physical disabilities, people who are obese, and people who are elderly. Why? People who have superficial characteristics that resemble the things our immune system associates with disease may provoke an unconscious aversive response in us – even if we are actually at no risk of infection from them.

Avoiding the foreign: xenophobia and ethnocentrism

Moreover, the behavioral immune system has been linked to both xenophobia and ethnocentrism. Several studies have shown that when individuals feel they are at heightened risk of infection, they prefer to be around familiar people, and tend to avoid those that are foreign. And in a political twist, they even change their attitudes toward immigration, showing a marked preference for more similar others and less willingness to accept immigrants who are “foreign.”

Moreover, women in their first trimester of pregnancy—a time when the actual immune system is suppressed and consequently, the behavioral immune system carries more of a burden—show higher xenophobic and ethnocentric attitudes. This suggests that we should be especially wary of such influences both when we are actually at greater risk of infection (as with pregnancy) and when we think we might be more vulnerable (as with times of extended media coverage of infections).

So what now?

I think it’s time to add the behavioral immune system to the long list of subconscious influences on our choices. We can’t help what it does (and we may have many occasions to thank it, when it does work as planned and helps us from getting infected with something unsavory) but by being aware of it, we can resist it when it’s leading us astray. Next time you just “have a gut feeling” that something is off-putting, ask yourself where it’s coming from. And maybe, with time, it will disappear in those contexts where it should never have appeared to begin with.


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