Trypophobia and the science of disgust

Editor’s note: Readers who feel an aversion to images of clusters of holes or roughly circular objects may wish to avoid scrolling down.

What’s the difference between smallpox and a strawberry? Between scarlet fever and a sea sponge, rubella and bubbles, or leprosy and beeswax? If these comparisons strike you as ludicrous, reward yourself with an Aero bar or a cappuccino. If, on the other hand, you find all of these as repulsive as flesh-eating maggots, there’s a chance you have trypophobia – fear of small holes.

Trypophobia is “unusual but common”, according to Geoff Cole and Arnold Wilkins, two University of Essex scientists who in 2013 described a condition “hitherto unreported in the scientific literature” in the journal Psychological Science. They suggested about 15% of the population might be trypophobic, based on sampling 286 individuals and discovering that 46 found the seed pod of a lotus flower “uncomfortable or even repulsive to view”.

The seed pods of the lotus flower are often cited as setting off trypophobia.
The seed pods of the lotus flower are often cited as setting off trypophobia.
Credit: Brian Vander Brug / Getty

One survey participant said the sight of asymmetrically placed holes made them “throw up in my mouth, cry a little bit, and shake all over”. Other distressing examples included soap bubbles and aerated chocolate. Significantly more women (18%) than men (11%) reported the aversion, though that might be an anomaly given the small size of the statistical sample.

Cole and Wilkins gave their paper the title ‘Fear of Holes’. Such a description of trypophobia would now not be considered particularly accurate. More recent research suggests it isn’t even really a phobia, having less to do with with fear than with disgust, and the response is provoked not just by holes but any cluster of roughly circular shapes, including bumps.

Trypophobia arose, the Essex researchers argued, in part because the “inducing stimuli” shared basic visual characteristics with dangerous organisms. They arrived at this conclusion using a complicated spectral analysis focused on the inverse relationship between luminance contrast and spatial frequency. It is not particularly important to understand what this all means, as the hypothesis has now been superseded; all one needs to know is that the analysis suggested aero bars and bubble bath shared visual similarities (or “spectral features”) with highly poisonous animals, to which some humans react at a deeply unconscious level.

Even something as seemingly innocent as a crumpet may provoke a trypophobic reaction.
Even something as seemingly innocent as a crumpet may provoke a trypophobic reaction.
Credit: Jill Ferry / Getty

The idea is that we are hardwired through evolution to avoid potential dangers, like spiders and snakes, without wasting time on conscious cognition. Any stimulus that resembles a dangerous animal may produce a reflexive aversion.

Which is an interesting theory, but probably wrong, according to An Trong Dinh Le, also of the University of Essex, and Tom Kupfer, of the University of Kent. In a paper published in the journal Cognition and Emotion in 2017, the two psychologists argue that trypophobia is an attempt to avoid a different threat: parasites and infectious diseases.

They note that many of the most virulent and deadly infectious diseases result in irregular clusters of pustules or roughly circular shapes on human skin, while parasites such as tics, botfly and jiggers also often form visible clusters of lesions on the skin.

A wasp’s nest may provoke feelings of unease.
A wasp’s nest may provoke feelings of unease.
Credit: Jose A. Bernat Bacete / Getty

“A pattern characterised by irregular clusters of roughly circular shapes may have been a reliable cue to the presence of pathogens,” they write. “It is plausible, therefore, that people who were readily able to detect these cues, and were motivated to avoid them, would have been less likely to incur the fitness costs of infectious disease.”

Which makes sense up to a point. But why should objects as innocuous as pomegranates or the frothy bubbles atop your coffee elicit the same strong aversion as signs of the pox?

According to Kupfer and Le, such overgeneralisation of fear responses from genuinely harmful to harmless but similar-looking stimuli is common in phobias and anxiety disorders.

Seeds in the skin of strawberries may also cause discomfort.
Seeds in the skin of strawberries may also cause discomfort.
Credit: Bernard Van Berg / EyeEm

For this ‘phobia’, however, they are confident the operative emotion is not fear but disgust, based on testing and comparing the fear and disgust responses of 255 people who self-diagnosed as trypophobic and a control group of 182 people with a normal relationship to cheese graters and beehives.

So rather than the straightforward “fear of holes”, Kupfer and Le conclude that it would be more accurate to describe trypophobia as “a predominantly disgust-based aversion to clusters of roughly circular objects”. Simple.

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