Looking back on social psychology’s greatest hits, my mind always drifts first to studies on conformity, largely because they make such good stories. Take Asch, for instance. Who would’ve thought that so many people would willingly follow the crowd in giving a blatantly wrong answer about line length? And then, of course, there’s Milgram. It is still shocking to imagine two-thirds of participants agreeing to shock another person up to the highest possible voltage. (Ok, so that’s technically obedience, not conformity, but you get the picture.)
Although studies of conformity fell out of fashion years ago, interest in the origins of conformist behavior are back in a big way, and the theorized reasons are definitely not what you might expect. In the latest issue of Personality and Social Psychology Bulletin, University of British Columbia researchers provide support for the Pathogen Prevalence Hypothesis, or the idea that higher prevalence of pathogens breeds higher levels of conformity. They use this hypothesis to explain cultural variation in how much individuals conform.

Sound a little out there? It actually starts to make some sense once the authors break it down. They start by explaining that beyond our physiological immune system, humans and other animals also develop a behavioral immune system which motivates us to pursue health-promoting behaviors in response to perceived threat of disease.

The behavioral immune system concept seems logical enough—when there’s a flu going around, we’re more conscious about washing our hands and staying away from sick people, and empirically, the authors cite evidence that under conditions of disease threat, xenophobia increases and extraversion decreases. The link to conformity, however, is a little trickier. Here’s their explanation: there are definitely cultural benefits to non-conformity, such as new inventions and discoveries. However, in times of major threat, communities must undergo a cost-benefit analysis of possible innovation versus definite safety, and safety always wins. Once a technique for reducing pathogen transmission seems to work, people tend to think they should just adopt it instead of reinventing the wheel, and values of conformity ensue.

This argument might work based on theory alone, but there is also a surprising amount of evidence to back it up. Using four measures of conformity—agreement with majority opinion, percentage of individuals that prioritize obedience as a value, variability in Big 5 personality traits, and percentage of individuals who are left-handed—the authors demonstrate that historical (but not current) pathogen prevalence emerges as a key predictor of cultural variations in conformity. The effect remains after controlling for things like GDP, population density, and collectivism.

Of course, as the authors freely admit, the data are correlational while the claim is causal, so we can’t make any definite assertions about the role of pathogen prevalence on conformity. It is at the very least, however, a thought-provoking theory. Just be wary if some wily social psychologist sneezes on you and then asks you to start estimating the length of lines.