The neural correlates of moral aversion and physical disgust using biographical memory

Moral thinking in humans is one aspect of behaviour that might set us apart from other species. Where did it come from? Why do we have morals? These are questions many philosophers, psychologists, anthropologists and more recently, neuroscientists are attempting to answer. One dominant hypothesis in the literature is that moral thinking has evolved from what is termed the basic emotion of physical disgust. A typical disgust response carries with it certain behavioural responses that aid in the avoidance of infection or disease. These behaviours include a characteristic facial expression, and other rejection behaviours such as gagging and nausea. Thus, if moral thinking has in fact evolved from our typical disgust response, we would expect some overlap in behavioural and neural responses to immoral and disgusting stimuli. The topic of this thesis is first, to evaluate the literature on moral cognition and review the evidence concerning the evolution of moral aversion from physical disgust. Second, in a carefully designed experiment using biographical memory, I test the hypothesis that there are differences between moral aversion and physical disgust. The results show some overlap as well as some differences in neural activity. I then conclude that because of the differences in neural activity, more evidence is needed to support the hypothesis that moral aversion has evolved from physical disgust.