Disgust is an emotion that is typically associated with things that are perceived as unclean, inedible, or infectious. In The Expression of the Emotions in Man and Animals, Charles Darwin wrote that disgust refers to something revolting. Primarily in relation to the sense of taste, as actually perceived or vividly imagined; and secondarily to anything which causes a similar feeling, through the sense of smell, touch, and even of eyesight. Disgust is one of the basic emotions of Robert Plutchik's theory of emotions. Disgust invokes a characteristic facial expression, one of Paul Ekman's six universal facial expressions of emotion. It is also associated with a fall in heart rate, in contrast, for example, to fear or anger.

Disgust may be further subdivided into physical disgust, associated with physical or metaphorical uncleanness, and moral disgust, a similar feeling related to courses of action.

Origins and development

Disgust is thought to have its origins in (and in some cases to be identical to) instinctive reactions that evolved as part of natural selection for behavior which tended to prevent food poisoning, or exposure to danger of infection. Disgust is frequently associated with waste products such as feces or urine, secretions from the human body (such as mucus), and with decomposing flesh, and insects, such as maggots, associated with it.

As in other human instinctual drives, disgust has an instinctual and a socially constructed aspect. Psychologist Paul Rozin has studied the development of feelings of disgust in children.

Jonathan Haidt is a researcher whose work involves exploring the relationship between disgust and various traditional concepts of morality. His theory of social intuitionism seeks to explain the apparently irrational and visceral reactions to violations of the moral order.

William W. McCorkle Jr. is an evolutionary anthropologist whose research has focused on the ritualized compulsion to handle dead bodies in special ways with regards to the activation of disgust and contagion systems in humans. McCorkle argues that contagion is not triggered by an actual threat, such as a toxicity of the human body; however, he proffers the theory that dead bodies trigger an aggregate number of mental systems involved in agency, Theory of Mind, and other systems linked to social intelligence which signal the potential threat of the corpse and any surrounding areas or predatory threats to individuals in the vicinity. This activation causes individuals to perform ritualized behaviors to corpses (and their remains/cremains). Moreover, McCorkle theorizes that contagion is an evolved psychological mechanism that utilizes biological warning systems such as disgust to trigger precautionary tags to sensory input in human minds from the environment for survival.