Disgust is an innate expression of rejection.

The expression evolved from vomit-like actions that were used to expel harmful foodstuffs. A perception that a substance is corruptive, toxic or harmful creates disgust. An object or action is thought of as distasteful and treated as potentially corrosive to health.
The lower jaw is pulled down, the lower lip is rolled outwards, and the tongue is moderately pushed out. The head arches back and pulls away from the offending substance. Often the eyes half squint whilst a short burst of air is blown through the lips as if clearing the mouth or throat of something distasteful. Instinctive gestures of pushing something away are common even when there’s no physical item to be pushed away. These are typical expressions of mild disgust. Extreme disgust can cause a person’s mouth to motion as if vomiting only air with a gaping mouth and tongue pushed fully out (gagging).
Over millions of years disgust has developed from an innate rejection of food to include a psychological appreciation of behaviours. Disgust has evolved to incorporate behaviours that people find distasteful. When these offensive behaviours are perceived, they trigger the original facial expressions for expelling foodstuffs.1 The higher intellectual processes of assessing behaviours, which are deemed unacceptable and then rejected, are nested upon evolutionary older processes concerned with rejecting food.2

Both psychologically and neurologically these processes are part of the same structures. The facial movements of disgust always come into play when people detect anything unusual in the appearance, odour or nature of their food. This is the main indicator of the evolutionary root of the emotion. Darwin first described this over 150-years ago.
Infants give the purest expressions of disgust when they taste something extremely sour or bitter. Their whole face is contracted to expel the substance. Eyes sometimes fully shut from muscle contraction as the mouth opens as wide as possible. The tongue is pushed out fully and held there. Whilst holding this impossible pose, they try to blow air out of their gaping mouth to aid the expulsion. As the substance is expelled, their whole body shudders as if from an ice cold breeze which is presumably also to help the distasteful thing on its way.

The expression of disgust in adults is the same only moderated. This is an unconscious action, which primarily turns the bottom lip downwards, accompanied with a modified oral expulsion of air in an expression like “uurrr”. This is often followed by a minor shudder that looks more for effect than purpose. This is now commonly related to psychological ideas almost as much as foodstuffs.

In our modern world, people who subjectively find the behaviour of someone in their group unacceptable can often be seen to unconsciously pull their head back whilst moderately pouting their bottom lip and tongue.
Faeces (poo or excrement) is a perfect example for inducing disgust. From an early stage in evolution humans have developed an acute sense of repulsion to anyone else’s and sometimes even their own. Through hundreds of thousands of years of avoiding faeces people feel instinctive disgust related to it. Whether it’s faeces on their trouser leg or faeces on their face, they instinctively feel uncomfortable with it being there. It’s definitely a detestable thing to think of as food. A simple thought of faeces displays disgust’s root.

People can use the above idea of faeces as a spring board analogy for any other form of disgust. If people perceive something to be potentially harmful to their health, they reject it. If people think behaviour will somehow affect them negatively, they can view that behaviour as disgusting. If people perform lots of degrading and shameful actions, they may be regarded as disgusting. Yet, on this last point, to say that a person is disgusting is less accurate than to say the thoughts or behaviours an individual expresses are disgusting. Addressing specific behaviours or substances is the effective way to tackle the revulsion of disgusting habits. A person is made up of many things. Unfortunately, people tend to get condemned by loose expressions of disgust – she is disgusting – rather than have a specific behaviour an individual exhibits addressed as disgusting.3

It can be difficult for people to separate actions from the people that perform them. When people have not washed for months, have slept on the streets, and carry potentially infectious bacteria wherever they go, it’s easy to think of them as disgusting. The only way people can be disgusting is by performing or not performing specific actions though. People in such situations can begin to believe they are innately disgusting – that they cannot modify their disgustingness. These thoughts can rob people of motivation to change. People can actually believe that no matter what they do they will always be disgusting. This is not true.
To clarify how much of an unconscious role perception plays in the disgusting process let us imagine you have an open wound on your leg covered with a plaster. The open wound is covered up and itching. It needs a scratch and that means the plaster needs to be removed. You want to know everything that is going on and look at the plaster closely as you remove it. It has soaked up a little blood, a bit of puss, and is red and yellow. You have only pulled it away a fraction from the skin. You could push it back and let it heal, but you remove the plaster completely and hold it in front of you. After a quick scratch, you decide, from nerves, to quickly put the blood and puss covered plaster back on the open wound to stop you picking it. Only now the thought of putting the plaster back on is disgusting. Perhaps, it’s now not clean and could cause infection?
The thought of putting something unclean on an open wound is disgusting. The question is when did the plaster become disgusting? When you partially removed it? When you completely removed it? Perhaps, when air was let in? Or maybe when the plaster was ten centimetres from the wound? Possibly, when it was twenty, thirty or forty centimetres from the wound? At some point in the process of removing the plaster you instinctively felt that it was now a potential risk. You began to think of your own healing bodily fluids as potentially infectious.

So in essence any substance or behaviour that could be seen as toxic or debasing, related to disease, could be seen as disgusting. Just as disease can be passed from one person to another, so can psychological expressions or memes. Ideas can cause us to act in degrading ways.

Disgust is a highly evolved emotion and extremely subjective in modern use. This is shown perfectly with the example of Darwin’s encounter with a native in Tierra del Fuego (located at the southern tip of South America) described in The Expression of the Emotions in Man and Animals. The naked native touched, with his unwashed fingers, some cold preserved meat which Darwin was going to eat. The native displayed utter disgust at its softness whilst Darwin felt utter disgust at a naked native touching his food with unwashed hands. The encounter provides a horizon-like scope of the different things people can find disgusting whilst not realising they themselves can seem disgusting too. Disgust is attributed to things in the outside world according to subjective views and social memes, like the texture of meat or a person fingering someone else’s food. Did the native not account for preservatives? Was Darwin concerned with bacteria?
This is all well and good when disgust is used in this way. Disgust, however, can be used by people to gain control over a social situation. People can express disgust at others, causing others to pause and consider if their actions are disgusting, and in so doing the others become passive and insecure. This allows the people expressing the disgust to dominate the situation. In this way, disgust is used as a control drama. People can express disgust to faze people into passive insecurity, which is a natural response, and then dominate at the other’s expense. Worse is attempting to persuade people that they’re disgusting, so as to compromise their psychological makeup. This is malicious, psychological abuse. It corrupts the internal frame of reference of people who become convinced they are disgusting when they are not. Children are susceptible to such influences. Also, as it will restrict people’s experience of life by making them avoid and neglect aspects of reality unnecessarily, troublesome consequences befall people if they are made to believe that things are disgusting when they are not.

There are consequences to experiencing disgust inappropriately.
When disgust is experienced, it changes the cognitive appraisals of the disgusted to more readily detect contaminants in their environment. If fact the ability to detect contaminents is directly attributed to the latter end of disgust’s development at around 6 to 7-years of age – the idea of contamination before this age is fairly meaningless. Whether it’s the texture of food or an intonation of expression, disgust amplifies people’s ability to spot potentially sickening features.
When disgust is being felt, it biasses cognitive decisions to unrelated things. People are more likely to sell their possessions at knock down prices and pay less than they would do normally for things. A deep sense of expelling something disgusting radiates into general decision making, and people are biassed towards pushing things away and not letting things in.
Accurate perceptions are important. They create an appropriate level of disgust. How disgusted people feel is important. Perceptions create emotions if they are accurate or not. If people believe a perception, they feel the associated emotion. Inaccurate perceptions of disgust can extremely restrict a person’s behaviour by misadjusting the intensity of the emotion concerned.

For example, some people fear attending public gatherings because other people have sat on the seats before them and potentially left bacteria behind. Strangers may have even put their shoes on the seats. This can be compared to things that people instinctively find disgusting: fluids that emerge from other peoples bodies; a dribble of milkshake that splats on the counter by the till as a women removes a straw from her mouth; standing in someone’s vomit. As the potential health risks are different, the perceptions should have different intensities of disgust. Sitting on an ordinary public seat should be the least disgusting, unless it’s covered in vomit.


Middle French. Desgoust = strong dislike, repugnance; the opposite of ‘to taste’.

1. That which pains or afflicts, or the passive feeling which it produced; troubled, affliction, vexation, sorrow.

2. Strong repugnance, aversion, or repulsion excited by that which is loathsome or offensive, as a foul smell, disagreeable person or action, disappointed ambition, etc.; profound instinctive dislike or dissatisfaction.