How is the behavioral immune system related to hygiene behaviors?

Infectious diseases present serious threats to our fitness. The biological immune system provides several mechanisms for dealing with these threats. So too does another system: the behavioral immune system. This second system is proposed to consist of a set of evolved cognitive, affective, and behavioral strategies for reducing the likelihood of infection, including xenophobia, traditionalism, and food neophobia. In the present work, we investigate how another suite of fairly novel culturally-learned disease avoidance strategies, namely hygiene behaviors and knowledge of germ theory, are related to the behavioral immune system. Across two studies from a university sample (Total N = 740; Study 1 N = 299; Study 2 N = 441, pre-registered), we find that individuals who engage more frequently hygiene behaviors show less evidence of reliance on several elements of the behavioral immune system (i.e., xenophobia, traditionalism, food neophobia). Similarly, individuals who know more about germ theory show less engagement of these behavioral immune system components. These findings suggest that effective cultural strategies for avoiding infectious disease may supplant older, evolved psychological strategies with the same purpose.