Disgust is not a pleasant feeling, but it is a very useful one. It prevents people from eating spoiled food or from sticking their fingers in feces or purulent wounds and then in their mouths. In this way, disgust protects against coming into contact with things that contain many pathogens and becoming infected in the process.
Because people are also disgusted with crawling animals, it is common doctrine that the emotion should also protect against parasites such as mosquitoes, lice or fleas. A team of psychologists led by Tom Kupfer from Nottingham Trent University in England now doubts that. In the science journal Proceedings of the Royal Society B. postulate that People have developed their own, independent protective mechanism to ward off parasites that crawl around on the skin.
The authors of the study write that the sight of things that contain dangerous infectious agents that shouldn’t get into the body triggers nausea and nausea. In contrast, that of ectoparasites, which attack humans from the outside in order to suck blood, for example, result in a much more sensible defense reaction against this type of attack: the need to inspect the skin, to scratch oneself and thereby remove the parasites.
The subjects had to look at meat with maggots and a bed full of bedbugs
In several experiments, the psychologists showed more than 1000 test subjects videos that each lasted exactly 90 seconds and in which either ectoparasites or possible sources of pathogens could be seen. They then asked the study participants about their emotions and physical reactions.
The test subjects had to watch a repulsive hodgepodge of video sequences: Among the scenes with ectoparasites was a kitten full of fleas, a bed full of bedbugs and a close-up of a blood-sucking mosquito.
The scenes with sources of pathogens showed, among other things, a piece of meat with maggots writhing in it, a violently festering wound on the arm and a black lump of ear wax. By far the most disgusting video showed dirty toilets that were recorded during a festival.
The psychologists did the experiment three times: twice in the US and once in China. The result was clear. In the scenes with fleas, bedbugs and mosquitoes, the subjects began to scratch and later reported that they had itchy, that “their skin tingled”, or that they had an irresistible urge to scratch.
On the other hand, when asked about their reactions to the videos of pathogen-contaminated places and things, they said sentences like “I was feeling sick”, “My stomach was spinning” or “I felt like I was about to vomit”.
The study authors rate this result as an indication that humans have developed various behavioral psychological mechanisms against ectoparasites on the one hand and against pathogenic viruses and bacteria on the other.
The observation that the reactions in people in the USA and China were basically the same suggests that the parasite defense is a cross-cultural mechanism. We have known this for a long time about avoiding contact with pathogens. No matter whether in India, Africa or Europe, the hit list of repugnance has the same things everywhere: feces, carcasses and pus.