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

Abstract

Disgust is expressed in response to sources of contamination and disease, and also arises in response to violations of moral norms. The overlap in these two functions had led some theorists to suggest that moral disgust may be an example of exaptation – the evolutionary 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 suggests that moral judgments may be driven by early affective processes, rather than by more recently evolved higher order cognitive functions. However, critics argue that disgust expressed in a moral context may simply be used either metaphorically to convey anger or to draw similarities with acts that are prototypically offensive. Therefore, the first aim of the current research was to examine whether disgust was uniquely implicated in moral judgment, over and above the emotion of anger. Using a variety of assessment tools, including facial electromyography, the first study in this thesis examined the specificity of the link between disgust and morality. Results showed that physical disgust at the trait, state and physiological level was more closely associated with moral transgressions than anger, indicating that expression of disgust in moral contexts is not simply metaphorical. Building on this, the next two studies provided a further examination of the link between disgust and morality within the context of obsessivecompulsive disorder (OCD) - a psychological disorder that is often characterised by heightened disgust and moral rigidity. Results showed that individuals with OCD experience stronger disgust than those with other forms of anxiety, and that trait disgust has a distinct impact on moral reasoning in individuals with OCD compared to individuals with other anxiety disorders. In the final two studies a clinical approach was adopted, providing the first investigation into the effects of a novel cognitive bias modification paradigm on disgust responding. The findings outlined in the five studies of 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 of pathological disgust.