Sex, Murder, and the Meaning of Life

Exploring the simple selfish biases that make us caring, creative, and complex

Do Unconscious Fears of Infection Affect Your Social Life?

The Behavioral Immune System IV

Mark Schaller is a professor at the University of British Columbia who has done a series of fascinating studies on the links between fear of disease and social psychology. 

Schaller argues that our brains have a behavioral immune system – which he defines as “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.”  The elegance of the behavioral immune system is that it can prevent the deployment of the more familiar physiological immune system – by getting us out of a potentially infectious situation without requiring our bodies to mount an energetically expensive, and potentially losing, battle with bacteria and viruses. 

Find a Therapist

Search for a mental health professional near you.

I’ve talked about some of the findings on the behavioral immune system in previous postings (The psychological immune system: When seeing me sneeze makes you healthier; The psychological immune system 2: When it’s healthy to be antisocial; and Behavioral Immune System III: Foul odors can trigger safe sex!) 

 Schaller himself wrote about the behavioral immune system for Scientific American (link below).  Schaller is a talented writer, a deeply thoughtful scientist.  In the article, he briefly reviews a range of fascinating studies linking fear of disease to prejudices (against old people, obese people, people in wheelchairs, and people from exotic foreign places), to personality self-ratings (people who are worried about disease rate themselves as less extraverted, and people who live is places with more disease are more avoidant of other people), to attraction (people living in disease-ridden places are more attracted to symmetrical partners), and even to the epidemic-level phobia of chocolate fudge (well, only when it’s shaped to look like dog feces). 

Schaller covers some fascinating research, including findings from a study by Carlos Navarrete and colleagues, showing that fear of disease changes pregnant women’s prejudices differently depending on trimester, in ways that make adaptive sense. As Schaller notes: “A woman's immune system is suppressed during the first few weeks of pregnancy, leaving her body more vulnerable to infection. One consequence is that women are more sensitive to sights and smells and tastes that trigger disgust. Another consequence is that, compared to women in later stages of pregnancy, women in their first trimester show higher levels of ethnocentrism and xenophobia.”

I highly recommend a look at Schaller’s article (the link is pasted below).

Related Links from Sex, Murder, and the Meaning of Life:

The psychological immune system: When seeing me sneeze makes you healthier.

The psychological immune system 2: When it’s healthy to be antisocial

Behavioral Immune System III: Foul odors can trigger safe sex!

Mark Schaller in Scientific American’s Mind Matters

The Behavioral Immune System: How unconscious fears of infection shape many aspects of our psychology.  Scientific American, June 14, 2011.

Douglas T. Kenrick, Ph.D., is professor of social psychology at Arizona State University.


Subscribe to Sex, Murder, and the Meaning of Life

Current Issue

Let It Go!

It can take a radical reboot to get past old hurts and injustices.