Disgust is one of the seven universal emotions identified by researcher Paul Ekman and is defined as a feeling of aversion towards something deeply distasteful or unpleasant. The emotion itself is experienced by all humans across all cultures, but may have culture-specific triggers, and may also be felt more by some people than others.

Like the other universal emotions, disgust is distinguished by a particular facial expression, characterised by a wrinkling of the nose that we would probably all recognise. Like other universal emotions, it must serve a purpose—but what is that purpose? This page explains more.

Defining Disgust

Almost all classifications of emotions agree that disgust is universal and central to being human.

Definitions also agree that it is a feeling of aversion towards something that is found deeply unpleasant (see box). This is often something poisonous or toxic.

The trigger can be something that is physically perceived through one or more of the five senses: a smell, taste or sight, for example. However, it can also be an idea, including one that invokes a moral standard. A word that is often associated with disgust is repulsive, expressing the idea that the trigger actually repels the person experiencing the emotion.

Common triggers of disgust include:

• Bodily excretions such as mucus, vomit and faeces;

• Anything that is rotting or diseased;

• Certain foods, especially those that are culturally unfamiliar;

• Injuries, especially if they expose bones or internal organs; and

• Sexual preferences that are perceived to be morally repugnant (although the precise definition of these preferences may vary by culture or individual).

Interestingly, for all that it is universal, disgust also appears to be learned, at least to some extent.

Children are often less triggered by things that adults find disgusting, such as blood, urine or faeces. Indeed, until the age of about four, children don't seem to feel disgust exactly, only distaste, a much milder form of the emotion. In fact, many children and adolescents are actually fascinated by things that often cause adults to feel disgust, hence the attraction of 'toilet humour' among these age groups.

It is also clear that some people are more disgusted than others by particular triggers. There are people who are made physically sick by certain smells, while other people have no issue with these smells. Similarly, some foods make people feel physically revolted, but others love them. This is often cultural in origin, suggesting that it is a learned behaviour. Interestingly, Paul Rozin, professor of psychology at the University of Pennsylvania and a researcher into disgust, suggests that most of the foods that actually disgust us—as opposed to simple dislike—are animal-based. This might therefore tie in with the idea of contamination or rotting, because rotten animal products are more likely than rotten vegetables to contain harmful microbes.

Recognising Disgust

Disgust is characterised by a particular facial expression:

• A wrinkling of the nose, both around the side and across the bridge;

• Lips drawn back from the teeth, so the upper lip is raised in what is described as an 'inverted u-shape', and the lower lip is raised and protruding; and

• Eyebrows lowered into a frown.

People often also make an involuntary sound often expressed as 'yuk', 'ew' or 'ugh'. They may also gag or choke, and even physically vomit.

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Why Do We Feel Disgust?

Disgust appears to have a very strong evolutionary purpose: to cause us to back off from things that may cause infection. It therefore helps to keep us safe and healthy.

This makes sense. Open wounds can harbour pathogens that might infect others. Rotting food can make us ill. Being in contact with infected mucus or vomit can also spread infection.

This also helps to explain why disgust is partly a learned phenomenon. Older people with more experience will have seen more things that may cause harm. It therefore makes sense that other people's disgust can be a strong trigger for our own, and that we learn from their experience rather than having to make our own potentially fatal mistakes.

It is also interesting to note that we generally do not feel disgust at our own faeces or other excretions. We also feel much less disgust about those of our immediate family than of strangers. This also seems to be evolutionary in its origin:

• We don't need to worry too much about the microorganisms in our own excretions because they came from inside our bodies, so we are already co-existing with them. We can therefore be slightly more relaxed about our own excretions (although we may still feel disgust about, say, diarrhoea, because that is likely to be the result of an infection with new and harmful pathogens).

• There is an evolutionary advantage to being able to tolerate vomit or faeces of immediate family members, because it means that we can bear to look after them. It would not be much help if parents couldn't change a child's nappy because they were so disgusted by the smell or sight. However, it has to be unpleasant enough that they will feel the need to change it relatively quickly to avoid the child developing nappy rash. Most parents would probably agree that this is a job to be endured, not enjoyed—but that it can be tolerated.

Harnessing and Overcoming Disgust

Disgust clearly has an evolutionary function—so should we always pay attention to it?

The answer to that is probably no, not always. It may pay to have a careful look about why we feel disgusted and ask whether it is justified. We might also look to see if some form of mitigation may be possible.

It is worth considering this more closely.

First, we might consider the issue of disgust caused by ideas or moral standards. We said that some forms of behavior may be disgusting, particularly if we consider them morally unacceptable. However, we should also ask if perhaps our moral standards may be outdated and therefore disgust is no longer the appropriate response. Sometimes it will be—some moral standards remain remarkably consistent. However, in other cases it will not.

This is a good example of using reason to test and then revise an emotional response to a situation.

What about disgust caused by physical sensations? We already know that disgust caused by bodily secretions and excretions is less extreme when a relative is involved, especially a dependent one. It is also possible to become less sensitised to disgust when you are exposed more to particular triggers. This is how doctors and nurses are able to operate on people, and dress wounds that would have most people reeling back in horror: they have seen it all before.

This is therefore an example of desensitisation to disgust: that familiarity makes everything more acceptable.

Interestingly, though, this may not work for everyone. Some people may become more disgusted because they have been traumatised by previous exposure to something that they found disgusting.

Healthcare is also a good example of the use of mitigation to address the causes of disgust.

The use of personal protective equipment is one way to reduce the risk of infection from open wounds or sick people. Similarly, parents caring for a sick child may wash their hands more often to avoid potential contamination. This mitigation may reduce the feeling of disgust, because the risk is known to be less.

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In Conclusion...

Disgust is a strong negative emotion with a powerful evolutionary function.

You ignore it at your peril. However, it is important to be aware that your reaction may be learned, and therefore not necessarily justified by the actual danger posed. You may also be able to mitigate a very real risk that your reaction has identified. It is therefore worth questioning your immediate reaction—even if you later conclude that it was justified.

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