A team of researchers from Nottingham Trent University, the University of California and Vrije Universiteit, has found that humans have two distinctly different reactions when disgusted—nausea and itchiness. In their paper published in Proceedings of the Royal Society B, the group describes experiments they conducted with volunteers being shown disgusting stimuli and what they learned from them.
Prior research and anecdotal evidence suggest that people react to things that disgust them in different ways—finding a tick or louse burrowing into a child’s scalp, for example, for most people, is likely to feel different than discovering the same child’s vomit or feces on the bathroom floor. In this new effort, the researchers wondered if nature has given humans different sorts of reactions for practical reasons.
The work began as some of the researchers noted that there appeared to be a pattern in the types of reactions people have based on the source of the disgusting event. They noticed that people tended to feel nauseous when confronted with something that might be an internal problem for them. Vomit on a bathroom floor, for example, might suggest an ailing child—a potential carrier of a disease, perhaps. It could also suggest the child ate something that others should avoid. On the other hand, people spotting a louse on the scalp of a child are more likely to respond with feelings of itchiness themselves—people hearing about a lice outbreak very often respond by scratching their own scalp even if not infected. Such a reaction, the researchers suggested, might serve as a warning to others, helping them prevent infection themselves.
To find out if their ideas might be correct, the researchers showed three groups of volunteers (two in separate locations in the U.S. and one in China, totaling over 1000 people) a host of disgusting videos they had found on YouTube, querying them after each video to see what sorts of feeling they had evoked.
The researchers found that the volunteers did indeed react the way they had predicted—by becoming nauseated when looking at videos of things that might impact their stomach or intestines and by feeling itchy to the point of scratching when viewing things that could bother their skin.