Fear, or Loathing?

Clusters of holes, as in these lotus seed pods, repulse people with trypophobia.

Joelan Brillo

Lotus seed plants. Honeycombs. Aerated chocolate. For some people, viewing such objects with clusters of holes turns their stomachs. The condition, trypophobia, is unusual but not uncommon. Its evolutionary origin is uncertain. Though it has been previously thought to be driven by fear, a new study suggests that trypophobia is driven by a sense of disgust.

To study the emotional and physiological responses underlying trypophobia, researchers at Emory University asked study participants to view and rate various images while their pupillary reactions were monitored with an eye tracker. The images included objects with multiple holes (e.g. lotus seed plants) and neutral objects (e.g. a pile of coffee beans), as well as images of threatening animals, such as spiders and snakes, which are known to trigger a fear response in our sympathetic nervous systems.

If trypophobia were primarily driven by fear, viewing hole images should cause a fight-or-flight response that widens pupils. Instead, the trypophobia-inducing images caused pupils to constrict. This response is associated not with the sympathetic nervous system, but with the parasympathetic nervous system, which handles the “rest-and-digest” unconscious aspects of our bodily activity. When triggered by noxious stimuli, the system slows our breathing and heart rate, as if telling the body to proceed with caution.

The researchers interpreted the pupillary constriction in reaction to clustered holes as a sign of disgust rather than fear, reasoning that such patterns could serve as visual cues that recall disgusting visual memories of rotting food or diseased flesh. “Based on anecdotal reports of people describing images of holes as ‘gross’ or ‘making their skin crawl,’ we actually weren’t surprised that our data revealed a parasympathetic response, which is consistent with disgust rather than fear,” says Stella Lourenco, an assistant professor of psychology at Emory University and coauthor of the paper.

Though study participants, on average, rated the holey images as more disgusting than the control images, none of the participants qualified as full-blown trypophobes on a trypophobia questionnaire. It seems, then, that intrinsic, albeit mild repugnance to hole-infested objects could be a broadly evolved trait in humans. (PeerJ)