From deontology to disorder: an examination of moral and pathological disgust

Abstract

Disgust is expressed in response to sources of contamination and disease, and alsoarises in response to violations of moral norms. The overlap in these two functions hadled some theorists to suggest that moral disgust may be an example of exaptation – theevolutionary process whereby the function of a trait shifts to serve a secondary purpose.This has important implications for our understanding of moral reasoning as it suggeststhat moral judgments may be driven by early affective processes, rather than by morerecently evolved higher order cognitive functions. However, critics argue that disgustexpressed in a moral context may simply be used either metaphorically to convey angeror to draw similarities with acts that are prototypically offensive. Therefore, the firstaim of the current research was to examine whether disgust was uniquely implicated inmoral judgment, over and above the emotion of anger. Using a variety of assessmenttools, including facial electromyography, the first study in this thesis examined thespecificity of the link between disgust and morality. Results showed that physicaldisgust at the trait, state and physiological level was more closely associated with moraltransgressions than anger, indicating that expression of disgust in moral contexts is notsimply metaphorical. Building on this, the next two studies provided a furtherexamination of the link between disgust and morality within the context of obsessivecompulsivedisorder (OCD) - a psychological disorder that is often characterised byheightened disgust and moral rigidity. Results showed that individuals with OCDexperience stronger disgust than those with other forms of anxiety, and that trait disgusthas a distinct impact on moral reasoning in individuals with OCD compared toindividuals with other anxiety disorders. In the final two studies a clinical approach wasadopted, providing the first investigation into the effects of a novel cognitive biasmodification paradigm on disgust responding. The findings outlined in the five studiesof this thesis provide novel evidence in support of an exaptation model of moral disgust,as well as a crucial first step in investigating novel adjuncts to the treatment ofpathological disgust