Resting parasympathetic activity is associated with malodor-induced change in perceived foreignness of speakers

Introduction: To protect against infection, individuals have evolved context-dependent pathogen-avoidant strategies, including selective social behaviors aimed at avoiding foreign individuals who may possess greater risk of infection. Parasympathetic nervous system (PNS) activity is associated with social engagement and regulation of the classical immune system but has not been widely investigated in relation to changes in intergroup perception and the behavioral immune system. Method: The current research investigated the relationship between parasympathetic activity and perceived foreignness of in and outgroup speakers during exposure to a pathogen-relevant odor (butyric acid). High-frequency heart rate variability was measured at rest and while participants rated foreignness of speakers with and without the odor present. Results: Findings show that exposure to the odor was associated with higher foreignness perceptions of outgroup speakers and lower foreignness perceptions of ingroup speakers. This effect was especially evident among individuals with higher resting parasympathetic activity. Conclusion: These results suggest that the PNS may play a role in changes in social perceptions during a behavioral immune response.