In his new study, one sufferer described the reaction to hole clusters: "[I] can't really face small, irregularly or asymmetrically placed holes, they make me like, throw up in my mouth, cry a little bit, and shake all over, deeply."
Even so, the phobia is not recognized as a disorder by the recently updated mental health manual, the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).
Cole's team wanted to know if trypophobic objects shared a common visual feature, so they compared 76 images of objects on a trypophobia website with 76 images of holes not associated with the phobia.
The images of trypophobic objects had high contrast at midrange "spatial frequencies" - repetitive spatial features of an image - compared with the nontrypophobic images.
They had the same visual structure as stripes, which can sometimes trigger migraines.
One trypophobic participant provided a clue to understanding the strong aversion to certain hole patterns: He reported having this same negative reaction to seeing a blue-ringed octopus, one of the world's most poisonous animals.
To investigate whether poisonous creatures could be causing the phobia, Cole and his colleagues analysed images of the blue-ringed octopus, the deathstalker scorpion, the king cobra snake and other poisonous snakes and spiders, finding that they all had high contrast at midrange frequencies, too.
Trypophobics' repulsive reaction to clusters of holes may be a side effect of an evolutionary adaptation to avoid poisonous animals, the researchers believe.
"We think that everyone has trypophobic tendencies even though they may not be aware of it," Cole said in a statement.
"We have an innate predisposition to be wary of things that can harm us."
Even people who don't fear such hole patterns rated the trypophobic images as less comfortable to look at, said Cole, who cured his own trypophobia by looking at the images so often he became desensitized.
To see how ingrained trypophobia might be, Cole's team is now studying how images of everyday objects, like watches, can be manipulated to make people prefer them more or less.
The study was detailed in the journal Psychological Science.
Read more: The ten most unusual phobias
- www.nzherald.co.nz