the skin enough to slide his hands in behind it and peels back the skin to expose the skull. Taking a hacksaw, he begins grinding his way into the skull, explaining to the audience, as he cuts, that due to the skull’s three layers, this can take some time. When he hears a change in tone he knows he’s through. ‘I am about to take the brain out,’ he calmly announces, as though it’s a cookery demonstration. The brain comes away surprisingly easily. He simply picks it up and lifts it out without resistance, like a walnut out of a shell. Nobody in the audience speaks. Their brows furrow and they lift their hands up to their faces, covering their mouths and half-masking their eyes. They are experiencing disgust.
Although it is such a basic emotion, disgust is often forgotten; if people are asked to list some common emotions it’s usually a long time before disgust is suggested. Yet of all the psychologists I’ve met who research different emotions, those who study disgust seem to do so with a particular passion. They told me that they have learned one thing, however, and the same applies here: however fascinating disgust might be, if you want to enjoy your food it’s not a good idea to read about disgust while you are eating.
There is one way in which disgust differs from many other emotions: feelings of disgust always have a clear cause. You can’t wake up one day feeling generally disgusted in the same way that you might feel generally sad. There has to be an object of your disgust and, as we’ll see, it’s these objects which provide clues as to the purpose of this strange emotion.
The loos at the Glastonbury Festival are infamous. By the end of the weekend after thousands of people have used them, they get very full. The story goes that every year, on the last day of the festival the same trick is played on one very unlucky toilet user. A group of people wait until a man has locked himself into the cubicle and then they tip over the entire box so that the unfortunate inhabitant is trapped lying in the contents of the now emptied toilet.
Just hearing about this story may well provoke a physical response in you. It certainly would for the victim of the trick. Disgust is a particularly visceral emotion. It can make you shudder, salivate, feel physically sick, retch and, at its most extreme, vomit. The facial expression for disgust is particularly distinctive: the nostrils narrow, the upper lip rises high, the lower lip lifts and protrudes slightly, the cheeks rise, the brows lower creating crow’s feet beside the eyes and the sides of the nostrils ascend, causing the sides of the nose to wrinkle. When a person is disgusted other people can tell exactly what they are feeling from those sneering lips. This is the disgust face and it appears very early in life.
how we learn to feel disgusted
Disgust is one of the earliest emotions that we experience. From birth, babies show disgust at bitter tastes and as Charles Darwin noted the expression of disgust gradually becomes more frequent. He became fascinated with the development of emotions after the birth of his first child and decided to document his son’s emotional expressions. More than thirty years later he wrote a book on the subject, a book which is often overlooked today. Darwin clearly observed disgust on his son’s face at the age of five months – on one occasion in response to cold water, on another at a piece of ripe cherry. ‘This was shown by the lips and whole mouth assuming a shape which allowed the contents to run or fall quickly out; the tongue being likewise protruded. These movements were accompanied by a little shudder. It was all the more comical, as I doubt whether the child felt real disgust – the eyes and forehead expressing much surprise and consideration.’
Whether or not babies do feel the emotion in the same way as adults, by the age of three toddlers have learnt what adults consider to be disgusting. Although babies and toddlers will happily play with their faeces they soon discover that they shouldn’t, suggesting that they only learn disgust through social conditioning. This is reinforced by a study which examined fifty children who had grown up in the wild; none showed any signs of disgust at bodily products. However, toddlers tend to learn disgust at faeces particularly easily, leading some such as Val Curtis, who researches hygiene and disgust at the London School of Hygiene and Tropical Medicine, to suggest that we are born with a propensity to find certain objects disgusting; it’s far easier to convince children to be revolted by faeces than by sweets. Having said that, it is impossible to disentangle the influence of socialisation. Inevitably it would be difficult to train a child to believe that sweets are disgusting because other children would soon undermine this view, whereas disgust at faeces is reinforced by every adult or older child they meet.
As children develop, their responses to disgust become more sophisticated. Imagine you go into a room where you’re given a glass of clean, fresh water. You drink some water and then you’re asked to spit into the glass before taking another sip. Would you do it? It is your own saliva after all and only moments before it was in your mouth. Then you’re given a fresh glass of water and a dead, but sterilised, cockroach is held in tweezers and dipped into the water. There’s nothing physically wrong with the drink in either case but when university researchers gave people these tasks most wouldn’t do it. At the age of four children will happily drink up, but by seven, like adults, they don’t want to. Before this age they might not possess the complex thought processes which would allow them to see contamination in the same (admittedly at times irrational) way as adults. An understanding of contamination requires the ability to follow a long chain of events. In order to feel repulsed by the idea of licking an object which has fallen on the floor, you need to consider that somebody who had previously stepped in dog faeces would have a dirty shoe which then touched the floor, thus contaminating the food, and finally you. By the age of seven or eight children’s thinking skills have developed to an extent where they can not only follow this chain, but can use disgust to their advantage with ploys such as licking the last biscuit and then offering it to their squirming sibling with the words, ‘Go on – eat it then!’
the disgusted brain
The fact that the facial expression for disgust is so striking reflects the significance of our ability both to convey disgust and to detect it in others. If one person tastes contaminated food everyone else needs to know to stay away from it. The disgust face is so central to this communication that the brain has a specific mechanism for detecting disgust in others. Mary Phillips and her colleagues at the Institute of Psychiatry in London asked volunteers to lie in a brain scanner while they were shown photographs of people displaying facial expressions of either disgust or fear. Cleverly, Dr Phillips set them the task of deciding whether the photograph was of a man or a woman in order to distract them from focusing on trying to identify the expression. Despite the fact that the emotion expressed was irrelevant to the task, the scan nevertheless demonstrated activity in different parts of the volunteer’s brain depending on whether the person in the photograph looked frightened or disgusted.
Deep inside the brain there’s a walnut-shaped area called the amygdala which has tended to be thought of as the seat of all the emotions but with disgust this proved not to be the case. Instead, two areas of the brain are stimulated by disgust – the basal ganglia and the anterior insula, which are both very old parts of the brain in evolutionary terms. People with Huntingdon’s disease have difficulty recognising expressions of disgust which is logical since Huntingdon’s damages the basal ganglia. Extraordinarily, even carriers of the Huntingdon’s gene who do not yet have symptoms of the disease have a reduced capacity for spotting the expression of disgust.
If you were to take a brain and peel back the temporal lobe or side of the brain and look deep inside, behind the ear, you would find a large pyramid-shaped structure known as the insula, a name derived from the Latin for island. The front of this pyramid or anterior insula is the area which responds when we taste strong flavours like salt. This neural link between disgust and taste is intriguing because it lends weight to the idea that disgust exists to protect us from contaminated food. The fact that disgust is found in such an old part of the brain might explain why it is an emotion which is so hard to overcome even when you know there’s no reason to find something disgusting. Even infants who have been born without functioning cerebral hemispheres show expressions of disgust at bitter tastes. This type of instinctive disgust involves no thinking, reflected in the fact that the insula is