Abstract: Pathogens and infectious diseases present strong selection pressures under which animals have over time evolved different extent of physical and behavioral immune adaptations. Owing to our unique brain evolution, humans have developed the most elaborate behavioral immune systems. From very early on, we seem to have relied on our various behavioral immune mechanisms to ward off diseases before they enter our body. When these disease defense mechanisms co-evolve with complex human group living, our social behaviors and attitudes serve the additional function of disease control. These include prejudice and discrimination against out-group members who are likely carriers of disease against which in-group members lack the physical immunity. These also include such in-group behavior as conformity and compliance which facilitate social learning and within-group cohesion partly to curb spread of disease in a group. These social behaviors and attitudes contribute to larger ideological and cultural differences including the individualism-collectivism distinction that in part defines different extent to which different human groups have historically had to deal with disease control issues due to their different geographically-based pathogenic conditions. As discussed in this review, these and other pathogen-related issues form much of our social psychology and the social behaviors and attitudes it studies.

Key words: pathogen threat, behavioral immune system, disgust, social cognition, evolutionary psychology