Common phobia you have never heard of: Fear of holes may stem from evolutionary survival response

For trypophobes, the sight of clusters of holes in various formations can cause intensely unpleasant reactions -- from serious migraines and panic attacks to hot sweats and increased heart rate.

New research by visual science experts Dr Geoff Cole and Professor Arnold Wilkins from the University of Essex suggests that trypophobia may occur as a result of a specific visual feature also found among various poisonous animals. The findings are published in Psychological Science, a journal of the Association for Psychological Science.

"These findings suggest that there may be an ancient evolutionary part of the brain telling people that they are looking at a poisonous animal," explained Dr Cole.

Although trypophobia has been widely documented by sufferers on the internet, it is still hardly known about and was only recently accepted by Wikipedia, who thought it was a hoax entry.

In one study, the Essex research team found that 16 per cent of participants reported trypophobic reactions. Despite this, there has been little scientific investigation of the phenomenon, leading Dr Cole to refer to trypophobia -- which he suffered from himself -- as "the most common phobia you have never heard of."

The research involved establishing if there was a specific visual feature common to trypophobic objects. They compared 76 images of trypophobic objects (obtained from a trypophobia website) with 76 control images of holes not associated with trypophobia. After standardising various features of the images, the researchers found that the trypophobic objects had relatively high contrast energy at midrange spatial frequencies in comparison to the control images. They had the same visual structure as stripes, which also cause migraines for some people.

The scientists then wanted to find out why this unique visual feature led to such aversive reactions. One trypophobia sufferer provided Dr Cole with a clue -- he had seen an animal that caused him to experience a trypophobic reaction.

The animal in question, the blue-ringed octopus, is one of the most poisonous animals in the world, which led Dr Cole to a "bit of a Eureka moment."

He and Professor Wilkins analysed images of various poisonous animals -- including the blue-ringed octopus, deathstalker scorpion, king cobra snake, and other poisonous snakes and spiders and found that they, too, tended to have relatively high contrast at midrange spatial frequencies.

The researchers at Essex concluded that trypophobia may have an evolutionary basis -- clusters of holes may be aversive because they happen to share a visual feature with animals that humans have learned to avoid as a matter of survival.

"We think that everyone has trypophobic tendencies even though they may not be aware of it," said Dr Cole. "We found that people who don't have the phobia still rate trypophobic images as less comfortable to look at than other images. It backs up the theory that we are set-up to be fearful of things which hurt us in our evolutionary past. We have an innate predisposition to be wary of things that can harm us."

As for a cure for trypophobia, Dr Cole suggests what worked with him -- he looked at the images so often he became desensitised to them.

In further research, the team from Essex are now exploring whether manipulating the spectral characteristics of images of everyday objects, like watches, leads people to prefer one object over another. They believe these experiments will shed light on just how ingrained trypophobic tendencies might be.