Arnold Wilkins, left, and Geoff Cole, right, hope to show that an aversion to objects such as lotus seedpods can be seen as a phobia with an evolutionary basis. (Roger Deeble)

During an introductory psychology course at Britain’s University of Essex in 2009, Arnold Wilkins asked his class to participate in a quick experiment. Wilkins projected two images on a wall and asked students to write down whether they found either of them disturbing. One was a photograph of a woody landscape. The other was a close-up of a lotus-flower seedpod — a flat-faced pod pocked with small holes. Most of the students were unmoved, but one, freshman An Le, recalls being both transfixed and revolted by the lotus image. “It felt like I was in shock,” he says.

Le is far from alone in his response. Thousands of people claim to suffer trypophobia, a term derived from the Greek “trypo,” which means punching, drilling or boring holes. It refers to an irrational fear of clusters of small holes, such as beehives, ant holes and even bubbles in a pancake on the griddle or air pockets in a chocolate bar.

On Web sites and blogs, self-diagnosed trypophobes share tales of vomiting, sleep loss and anxiety attacks at the sight of such objects as honeycombs and rotting wood. They say the fears are haunting and disruptive of their daily lives.

But the medical world hasn’t yet embraced the phobia as real. Trypophobia isn’t listed in any major dictionary or in the Diagnostic and Statistical Manual of Mental Disorders. Attempts to add trypophobia to the Oxford English Dictionary and even to establish a Wikipedia page have been rebuffed because there hasn’t been any research published on the subject. A Wikipedia editor who deleted an entry on trypophobia in 2009 noted that trypophobia is “likely hoax and borderline patent nonsense.”

Tammy Swallow Batten, a 38-year-old paralegal from North Carolina said that even her therapist was dismissive of her fears, telling her “to get more exposure to holes and it wouldn’t affect me anymore.”

“No one really takes it seriously,” she wrote in an e-mail. “I think that therapists are skeptical of the impact this phobia has on everyday life.”

Wilkins, an expert on visual stress, and an Essex colleague, Geoff Cole, are hoping to change that. They say they are the first scientists to investigate the visual elements behind the phobia. Their study is currently under peer review by the journal Psychological Science.

“Trypophobia touches on so many different areas — phobias, evolution and ancient selection pressures, psychology, visual stress, rapid object recognition and neuroscience,” says Cole, who proposed the idea of the study to Wilkins after reading about the condition on the Internet.

Phobias can develop for a variety of reasons. They can be learned (a fear of heights triggered by seeing other people be scared of heights, for example), the result of traumatic experience (a fear of dogs that stems from being being bitten by a dog) or the result of biology (people who are, say, prone to anxiety). Wilkins and Cole believe trypophobia has biological roots.

But thus far, most of their research has focused on identifying what types of images set off these reactions rather than why. In 2011, the pair conducted a series of experiments to discern the extent to which trypophobic images disturb people. They showed a group of people pictures — of rotting tree trunks, holey cheese and the lotus seedpod — interspersed with images of landscapes and other features of nature. Participants marked whether each image made them feel any discomfort.

About 16 percent of the 286 people surveyed were upset by images the scientists had identified as inducing trypophobia; the remaining 84 percent were upset by none of the images. Wilkins and Cole then analyzed the characteristics of these images and found a commonality in their compositions. Trypophobic images, they say, are marked by a high contrast of detail, which makes them stand out to our eyes.

No one is sure why this leads to such a sense of disgust in some people and not in others. But Wilkins and Cole say trypophobia’s roots run deeper than socially produced fears such as triskaidekaphobia (fear of the number 13) and might upend established theories about our natural defense mechanisms.

“We think the human system may have evolved because of an unconscious visual structure, not from exposure to poisonous animals,” Cole says. He and Wilkins posit that trypophobic images set off a “trigger feature” in some people, much like the “fight-or-flight” response to the perceived danger of a snake.

In a separate experiment, the pair showed people slide shows of various images and monitored their brain activity via functional MRI scans. “You get an abnormally high response with the trypophobic images,” Wilkins says. “It’s like these poisonous things are warning us that they’re poisonous,” Cole says. Trypophobic patterns, such as those that can be found on the skin of snakes and spiders, are indicative of poisonous predators, and some people are especially primed to respond to that. Wilkins and Cole hope to soon figure out why.

“It’s interesting from a practical point of view because so many people have it,” Cole says. “But also it’s interesting from a theoretical point of view why it occurs and what it says about human evolution.”

Others suggest that trypophobia is simply the manifestation of collective disgust toward certain images.

The aversion to holes in organic material could more simply be explained by a dislike of sights we associate with disease and decay, says Martin Antony, a professor of psychology at Ryerson University in Toronto and author of “The Anti-Anxiety Workbook.” It’s not necessarily cause to consider the condition a true phobia, he says.

“People can learn to be afraid of anything,” Antony says. “It’s not unusual for people to have aversions to imagery or sounds or textures. I’ve seen people terrified of Q-tips.”

To Masai Andrews, a 29-year-old agent at the New York State Office of Mental Health in Albany, trypophobia is very real. As a child, he says, he had to avoid looking into shower heads and was deeply disturbed by worm holes left in the mud after a night of rain. He says he once vomited at the sight of a doctored image of a lotus seedpod online.

“I can go all day subconsciously averting my eyes from, say, the tread on someone’s shoe that I find revolting or the undulating fish gills in the tank at the doctor’s office,” Andrews wrote in an e-mail. In 2009, Andrews created, a Web site dedicated to raising awareness about the condition, and a trypophobia Facebook group that has grown to more than 6,600 members.

Wilkins and Cole concede that it’s too soon to draw major conclusions from their findings. For now, they are outlining a desensitization regimen whereby trypophobes gradually expose themselves to more disturbing imagery as a way to overcome their anxieties, Wilkins says. “But it probably won’t be possible to remove the uncomfortableness altogether.”

Thomas is a science and technology writer in the San Francisco Bay area.