Disease avoidance is one of the main roles of olfaction. In particular, body odors are universal elicitors of disgust, a core emotion that plays a key role in disease avoidance. The disease avoidance theoretical framework emphasizes psychological mechanisms – attitudes and behaviors – aiming to recognize and evade pathogen threats. Thus, it focuses on behavioral immune defenses and disgust, which often evokes such attitudes and behaviors. Importantly, the quality of body odors changes with sickness, and thus olfactory disease detection is possible. Body odor disgust sensitivity (BODS) might reflect a behavioral disposition to avoid pathogens, and it may also involve social attitudes that prefer limited contact with strangers. The general aim of this thesis was to investigate the connection between olfaction, (body) odor disgust, and social attitudes from the perspective of disease avoidance.

In Study I, I investigated the relationship between disgust sensitivity to body odors and prejudice. Using an online survey, I found that high levels of BODS were associated with stronger prejudice towards a fictitious refugee group and that this relationship was partially explained by perceiving the group as different in terms of food, hygiene, and sanitary practices. In Study II, I looked at the association between olfactory stimulation, BODS, and implicit bias toward an outgroup. BODS levels were positively related to implicit bias towards an outgroup; however, this bias was not affected by olfactory cues. In Study III, I aimed to see if the relationship between BODS and prejudice generalizes across different cultures and locations. I found that higher BODS levels were associated with more prejudiced attitudes towards a fictitious refugee group across nine countries on all continents. As in Study I, this relationship was partially explained by perceived dissimilarities of the refugees’ norms regarding hygiene and food preparation, and general attitudes toward immigration. In Study IV, I investigated the relationship between the self-reported body odor disgust and perception of real odors, showing that individuals with higher BODS levels perceived smells as more highly valenced overall: unpleasant smells were rated as more unpleasant, and pleasant smells were rated as more pleasant.

Overall, the research presented in this thesis supports the idea that there is a link between olfactory disgust and prejudice, which can be explained by disease avoidance behaviors.