Disgust

Definition

Although there is much dispute about exactly what emotions are, everyone, starting with Charles Darwin in the 19th century, agrees that disgust is one of them. Disgust is almost always considered a basic emotion, often along with anger, fear, sadness, happiness, and surprise. Basic emotions, as defined most clearly by the psychologist Paul Ekman, are differentiated from more complex emotions on the grounds that basic emotions have some presence in nonhuman animals, are expressed and recognized universally in humans, and have a distinct facial expression.

Although disgust was clearly described by Charles Darwin in 1872 in his classic work, Expression of Emotions in Animals and Man, unlike anger, fear, and sadness, it was studied very little in psychology until the past few decades.

Behavioral, Expressive, and Physiological Responses

Like other basic emotions, the elicitation of disgust causes a set of predictable responses. Behaviorally, there is a withdrawal from the object of disgust. There is a characteristic facial expression, including a closing of the nostrils, a raising of the upper lip, and sometimes a lowering of the lower lip (gaping). The lowered lip is sometimes accompanied by tongue extension. Physiologically, the signature of disgust is nausea. Unlike fear and anger, the two most similar basic emotions, disgust is not accompanied by physiological arousal (e.g., increased heart rate). These three types of response (behavioral, expressive, and physiological) are generally accompanied by a feeling of revulsion.

Elicitors

It is in the domain of understanding the elicitors of disgust that the greatest challenge is encountered. So many things can elicit a disgust response. It is natural to look at nonhuman animals to get an idea of the basic core or origin of disgust. An expression very much like the human facial expression of disgust is seen in many mammals. It typically occurs in response to tasting a food that is either innately unpleasant (like something very bitter) or something that has been associated with nausea (e.g., a contaminated food). This fact, plus the fact that the disgust facial expression functions to eject things in the mouth and close off the nostrils, suggests that disgust, in its primitive form, is about food rejection. Further evidence for this comes from the very name of the emotion, disgust, which means bad taste. And the nausea that is part of the disgust response has the very specific effect of discouraging eating. These facts caused Darwin to describe disgust as a response to bad tastes and caused the psychoanalyst Andras Angyal to described disgust as a form of oral rejection based on the nature of a particular food.

This type of bad taste or distaste disgust seems to be the origin of disgust and may be a way that animals both reject food and communicate to other members of its species that a particular food should be rejected. Similar expressions and functions for distaste can be observed in human infants. However, by the age of 5 years or so, humans show disgust responses to many potential foods that neither taste innately bad nor have been associated with illness. Feces is a universal disgust, acquired in the first 5 years of life, along with disgust responses to other body products, rotted foods, and many types of animals (such as worms and insects, depending on the culture). Almost all foods that produce a disgust response are of animal origin. From about age 5 on, the human disgust response shows a uniquely human feature: contamination sensitivity. If a disgusting entity (say, a cockroach) touches an otherwise edible food, it renders that food inedible. This is not true of distasteful substances (such as a bitter food) for humans, and no animal (or human infant) has been shown to show the contamination response. Some believe that true disgust is a distinctly human response that uses the same expressive system as the distaste response seen in human infants and nonhuman animals but is a response not to the sensory properties (e.g., bitterness) of a food but rather to its nature or origin. People find worms disgusting because of what they are and not because of what they taste like (most people don't even know what they taste like).

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