We are prejudiced against all kinds of other people, based on superficial physical features: We react negatively to facial disfigurement; we avoid sitting next to people who are obese, or old, or in a wheelchair; we favor familiar folks over folks that are foreign. If I asked you why these prejudices exist and what one can do to eliminate them, your answer probably wouldn’t involve the words “infectious disease.” Perhaps it should.
What does infectious disease have to do with these prejudices? The answer lies in something that I’ve come to call the “behavioral immune system.” The behavioral immune system is our brain’s way of engaging in a kind of preventative medicine. It’s a suite of psychological mechanisms designed to detect the presence of disease-causing parasites in our immediate environment, and to respond to those things in ways that help us to avoid contact with them. This has many important implications – for prejudice, for sexual attraction, for social interaction, and even for the origins of cultural differences. (And, yes, for health too.)
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