Things Rank and Gross in Nature: Psychological, Physiological and Neuroimaging Investigations of Sociomoral Disgust

Much like unpalatable foods, filthy restrooms and bloody wounds, sociomoral transgressions are often described as “disgusting”. This linguistic similarity suggests that there is a link between sociomoral disgust and more rudimentary forms of disgust associated with toxicity and disease. Critics have argued, however, that such references are purely metaphorical, or that sociomoral disgust may be limited to transgressions that remind us of more basic disgust stimuli. My aim was to provide more direct evidence that sociomoral transgressions do genuinely evoke disgust, and to explore factors that may influence how much disgust is evoked. I first searched for similarity in the facial expressions evoked by gustatory distaste (elicited by unpleasant tastes), physical disgust (elicited by photographs of contaminants), and moral disgust (elicited by unfair treatment in an economic game). I found that all three states evoked activation of the levator labii muscle region of the face, characteristic of an oral-nasal rejection response and consistent with an origin of sociomoral disgust in oral disgust. I next investigated whether individual differences in the tendency to experience physical disgust are related to variability in sociomoral judgement and emotion. In two different populations, heightened sensitivity toward physical disgust was related to more severe sociomoral judgements. A complementary neuroimaging study showed overlap between the neural correlates of physical disgust and sociomoral judgement, as well as highlighting brain regions that may underlie sociomoral hypersensitivity. Finally, I tested the idea that perceived differences in the causal stability of sociomoral transgressions may specifically affect levels of disgust. Although it was not possible to dissociate disgust from anger, the transgressions that were presented did evoke reliable self-reports of disgust. Taken together, these findings converge to support the conclusion that sociomoral transgressions can in fact elicit disgust, and accordingly that references to the disgusting nature of wrongdoing reflect biological reality rather than metaphor.Ph