Immunity in the Mind

Do our own prejudices and perceptions of people help defend our bodies against infectious disease?

An article published in the April issue of Current Directions in Psychological Science, a journal of the Association for Psychological Science, suggests that our brains contain a sort of “behavioral immune system” that defends against disease even before disease-causing pathogens reach our bodies. Mark Schaller, of the University of British Columbia, who co-authored the article with Justin H. Park from the University of Bristol, suggests that a host of psychological factors combine to detect and avoid potentially infectious things in our immediate environment.  This provides a “crude” first line of defense against infection, and reduces the workload of the “real” immune system.

This affects our interactions with other people. One study reviewed by Schaller and Park found that when people felt more vulnerable to infection, they were less extroverted.  Another study on worldwide personality differences revealed that people are generally less extroverted in countries where infectious diseases have historically been highly prevalent. Many other studies suggest that the threat of disease may contribute to prejudices against people who look or act in ways that seem unusual.

However, the authors are quick to point out that many of these prejudicial responses are erroneous and costly. Blemished skin, for example, may be perceived as infectious when it is not. “This system is designed to identify things that might be infectious, but it relies on imperfect cues,” says author Mark Schaller.  “One consequence is that it may often lead us to avoid things, and people, that pose no risk at all.” He suggests that research on the behavioral immune system can help scientists uncover the hidden causes of many prejudices and, therefore, be better prepared to intervene and undo those prejudices.

Research on the behavioral immune system may also have health benefits.  According to the review, new research shows that when people see potentially infectious things in their environment, it may lead the “real” immune system to respond more strongly to actual infection.