Wholly Unnerving

Training a flashlight on a surprisingly common fear

The fear of holes, or trypophobia, is linked to a physiological response more associated with disgust than fear, according to a new study published in PeerJ.

Trypophobia is not officially recognized in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders. But many people report feeling an aversion to clusters of holes—such as those of a honeycomb, a lotus seed pod, or even aerated chocolate.

“Some people are so intensely bothered by the sight of these objects that they can’t stand to be around them,” says Stella Lourenco, associate professor of psychology, whose lab conducted the study. “The phenomenon, which likely has an evolutionary basis, may be more common than we realize.”

Previous research linked trypophobic reactions to some of the same visual spectral properties shared by images of evolutionarily threatening animals, such as snakes and spiders.

It is well-established that viewing images of threatening animals generally elicits a fear reaction in viewers, associated with the sympathetic nervous system, called the fight-or-flight response, in which the heart and breathing rate goes up and the pupils dilate. The researchers wanted to test whether this same physiological response was associated with seemingly innocuous images of holes.

They used eye-tracking technology that measured changes in pupil size to differentiate the responses of study subjects to images of clusters of holes, images of threatening animals, and neutral images. Unlike images of snakes and spiders, images of holes elicited greater constriction of the pupils—a response associated with the parasympathetic nervous system and feelings of disgust.

In contrast to a fight-or-flight response, a parasympathetic response slows heart rate and breathing and constricts the pupils. “These visual cues signal the body to be cautious, while also closing off the body, as if to limit its exposure to something that could be harmful,” says Vladislav Ayzenberg 22PhD, a graduate student in the Lourenco lab and lead author of the study.

The authors theorize that clusters of holes may be evolutionarily indicative of contamination and disease—visual cues for rotten or moldy food or skin marred by infection.

The subjects involved in the experiments were college students who did not report having trypophobia. “The fact that we found effects in this population suggests a quite primitive and pervasive visual mechanism underlying an aversion to holes,” Lourenco says.

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