Disgust, an emotion that most likely evolved to keep us away from noxious substances and disease, seems especially active in our moral lives. People report feeling disgust in response to many immoral acts (eg, Rozin et al. 1999), make more severe moral judgments when feeling disgusted (eg, Wheatley and Haidt 2005), and are more likely to view certain acts as immoral if they have a tendency to be easily disgusted (Horberg et al. 2009). Yet, despite the wealth of evidence linking disgust and morality, the reason for the link remains unclear. This may be because the bulk of empirical work on the topic has been aimed at simply demonstrating that disgust and moral judgment are connected—a claim that, given the influence of rationalist models of moral judgment such as Kohlberg’s (1969), is novel and surprising. Fewer researchers have attempted to explain why disgust and moral judgment should be so connected (for recent exceptions, see Kelly 2011 and Tybur et al. 2012). Here, we present an attempt to do so.

Our primary claim is that disgust functions as part of a general motivational system that evolved to keep individuals safe from disease. As such, disgust motivates negative evaluations of acts that are associated with a threat of contamination (eg, norm violations pertaining to food and sex); negative attitudes toward unfamiliar groups who might pose the threat of contamination through physical contact (eg, outgroups characterized by these norm violations, or who are unfamiliar); and greater endorsement of certain social and political attitudes that minimize contamination risk (such as increased sexual conservatism, reduced contact between different social