Determining neurophysiological responses to physical and moral disgust elicitors–A systematic literature review

Disgust is a common basic emotion with evolutionary roots in helping to avoid contaminants and illness. Moral disgust, however, is often reported in response to witnessing a moral violation or social boundary being crossed. Previous research has sought to understand if moral disgust is its own emotional state which derives from the more basic physical disgust, or if it is a blend of different emotions. To elucidate this relationship further, this review sought to systematically evaluate the methods in which research which has measured either physical disgust or moral disgust responses and identify common and separate physiological and neurological markers of these emotions. The review highlights that whilst there are common markers shared between physical and moral disgust, that this commonality depends instead on the type of moral violation or physical disgust elicitor. It is suggested that physical core disgust, and bodily moral or purity disgust are closely related, whereas physical animal-reminder disgust and socio-moral violations might elicit responses similar to anger or fear. The review recommends important considerations for future investigation of moral emotions, and highlights how stringent control of disgust elicitors is necessary to accurately measure the physiological and neurological markers of different types of disgust. Furthermore, the review highlights how other important considerations such as intention behind a violation and differences in perceived severity of different types of violation.