Is 'Sexual' a Sub-type of Disgust, or is it a Separate Basic Emotion?

Disgust is a crucial emotion that guides a variety of avoidance and rejection behaviours in humans. These avoidance behaviours function to keep us safe from potentially harmful stimuli. A current adaptationist theory proposes three distinct sub-types of disgust based on their unique adaptive function, called the 'Three Domains of Disgust,' (pathogen, moral and sexual) (Tybur et al, 2013). The function of pathogen disgust is to maintain physical health through the avoidance of infectious and disease-causing agents; the function of moral disgust is to maintain group cohesion by avoiding or punishing moral transgressors and the function of sexual disgust promotes reproductive success through the avoidance of unfit mating opportunities. The theory holds that moral and sexual disgust co-opted pathogen disgust mechanisms to solve new adaptive problems. According to discrete emotion theory, subtypes of a basic emotion share: neural profiles, physiological and behavioural signatures. Therefore, if moral and sexual disgust co-opted pathogen disgust mechanisms, then common behavioural and neural mechanisms should emerge in response to stimuli in the three domains. In this thesis, I undertake four experiments to explore the behavioural and neural correlates of the three domains of disgust. I use linguistic stimuli and manipulate the semantic properties of sentences and words such that each category induces disgust, although still resembling its distinct sub-type. Overall, the results from each experiment reveal that the sexual category differs from both pathogen and moral categories. I tentatively propose that the sexual response is not a form of disgust but could be considered a distinct discrete emotion.