So Dr. Kupfer along with Sonia Alas and Tiffany Hwang, then undergraduate students at U.C.L.A., pored through YouTube. They watched and debated for hours in order to select the most rank and vile footage possible. Many options were too weak, such as footage of “mildly moldy food,” Dr. Kupfer said. “We wanted feces, we wanted some sort of infection,” he clarified.
Dr. Kupfer’s dream came true. The final ectoparasite clips included a kitten riddled with fleas, a nightmarish bed bug infestation and a beauty shot of a mosquito sucking blood. The final pathogen clips included meat pulsing with maggots, an infected arm lesion oozing pus — Dr. Fessler called it the “pus volcano” — and a clump of earwax as dark as an asteroid.
The meat was Dr. Kupfer’s own creation; unable to find an adequately disgusting video of rotten food, he left a slab of meat in his garden for two weeks and returned when it “seemed maximally disgusting,” he said.
The video that the researchers found most disgusting — titled “Dirty festival toilets” in the paper’s supplementary information — has since been removed from YouTube. This, perhaps, is for the best. I tried to watch every video used in the experiment. I did not vomit, but I did experience heart palpitations and had to sit in my bathroom with the lights off for several minutes until I stopped seeing the pus volcano. Missing out on the dirty festival toilets, it seemed, was an act of self-care.
The researchers conducted essentially the same experiment three times, twice in the United States and once in China, surveying in total more than 1,000 people. In all three surveys, participants had distinct reactions to the ectoparasite videos when compared with the pathogen videos. When watching ectoparasites, participants reported more urges to itch and scratch, theoretically protecting the surface of their skin from danger. And when watching pathogens, the participants reported more feelings of nausea and urges to vomit.
The researchers plan to expand this project internationally to see how ectoparasite disgust responses vary in different countries and in different languages. Understanding the nuances of disgust, they say, could inform our understanding of disorders such as delusional parasitosis, the mistaken belief that parasites have invaded the body.
Bunmi O. Olatunji, a psychologist at Vanderbilt University who was not involved in the research, said that he considered the new paper’s results too preliminary to make inferences about clinical conditions. But it does offer “interesting possibilities for thinking about the mechanism by which disgust may contribute to the development and maintenance of skin-picking disorder.”