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We open the refrigerator in search of something good to eat, but as soon as the door opens up, a revolting smell hits us and in response the mouth pulls the corners down. Having identified the cause of the nauseating smell, a piece of greenish cheese covered with mold, forgotten behind the eggs, our forehead fills with wrinkles and the nose curls. Holding the arm well extended, we grasp the food that has gone bad between the thumb and forefinger and, with the face more and more contorted by repulsion, we throw it in the damp, with the ruined appetite and with a slight sense of nausea, if not even with a retching.

This, more or less, is what happens to the face and our body when we run into something that repels us: we feel disgust, one of the primary emotions on a par with fear, sadness, joy, anger and surprise. Usually, it is revolting flavors that trigger it, but even by smelling, touching and looking, you can be caught by this reaction. But what's the use?

emotions, disgust Insects for lunch? For the populations of Western countries it is a revolting idea, for others it is normal. | Shutterstock

Warning sign. "Disgust has had an important evolutionary function, " explains Francesco Mancini, professor of clinical psychology at the Guglielmo Marconi University of Rome. "It is a biological mechanism that protects us from the ingestion of toxic and harmful substances, and has evolved in our ancestors as a defense tool against diseases and infections." In fact, running around the savannah by putting it in your mouth or touching everything would have been extremely dangerous, without that alarm bell that makes us move away from an unpleasant smell, it induces us to spit a repulsive food or it puts us in flight from what appears to us repellent.

emotions, disgust The mucus is one of the so-called "universal crap". | Shutterstock

The same for everyone? According to Paul Rozin, a professor of psychology at the University of Pennsylvania (USA), everyone, without distinction, is disgusted by faeces, urine, blood, mucus, saliva, vomit, purulent wounds, body parts, corpses, viscera and disease-carrying animals, like insects and mice.

However, beyond universal rubbish, each people and country has its own tastes and disgusts, which depend on history, the environment and the cultural context. "Every population has" elected "its own repugnant substances, especially in food ", continues Francesco Mancini. "For us westerners, for example, it is disgusting even today to imagine eating insects, while for the Asian and African populations it is a normal custom." Similarly, for Muslims it is disgusting to feed on pigs and for Hindus of cattle.

The moral disgust. "But the emotion of disgust is also aroused by behaviors, actions and people who act in ways that we believe are corrupt and that endanger social integrity", continues Mancini. "In fact, with the structuring of humanity, basic disgust has also evolved into moral disgust. In front of two shirts, both washed and ironed, but one belonging to a clerk of a family father bank and the other to a pedophile who is serving his sentence in jail, we would certainly choose to put that of the "clean" man. Wearing the pedophile's shirt would cause us a moral disgust. "

Image This article is based on a recent issue of Focus Extra. Find out what you find in the last issue on newsstands in recent weeks. | Focus EXTRA

Faced with a heap of nauseating dirt and a person who has committed a heinous crime, our face takes on the same expression of disgust . And disgust is so powerful that even clean objects, but associated with the idea of ​​dirt, are enough to trigger it.

This explains what happened several years ago in some US pediatric hospitals. To the directions it was reported that nurses drank fruit juices intended for children, which remained dry-mouthed. "The problem was solved by replacing the normal glasses with containers similar to those used for urine collection, " says Mancini. The children didn't notice; but nurses, used to using them for a completely different purpose, no longer used them for drinking.

Contagious! What happens in the brain when we are disgusted? The most involved region is the insula, a portion of the cerebral cortex. If an accident or illness damages it, the aversion to foods that were previously thought to be inedible disappears, and it also becomes difficult to recognize facial expressions typical of this emotion.

Neuroimaging studies have also shown that disgust is contagious. In one of these, published in Neuron and conducted at the Institute of Neuropsychology in Marseille (France), some volunteers were made to smell a foul- smelling liquid , while other people looked at them. The brain activity of the latter, as well as the expression that took on the face, followed those typical of those who are disgusted.

emotions, disgust Women are generally more prone to disgust than men. Perhaps to protect children, as well as themselves, from dangers. | Shutterstock

More picky women. However, the propensity to experience repugnance is an individual trait. "We are not all sensitive in the same way, " Mancini points out. "Women, for example, are more prone to disgust, perhaps because this emotion protects not only themselves but also their offspring."

According to Daniel Fessler, evolutionary anthropologist at the University of California, Los Angeles (USA), even the nausea typical of the first three months of pregnancy have a protective function: in this period, in fact, the immune system of women is less effective, and stay far from what can cause diseases, to themselves or to the fetus, it is therefore more important.

Article prepared on the basis of a work by Paola Grimaldi, on Focus EXTRA 76.