Out of this world: student can voluntarily adjust the size of his pupil


  • A man in Germany can voluntarily shrink and enlarge his pupils, according to a new case report.
  • The 23-year-old student said he started doing it when he was about the age of 15 or 16 after he “played computer games for long periods of time.”
  • Impossible as it may seem, he was able to do it by just concentrating on his eyes.

A 23-year-old student in Germany can shrink and enlarge his pupils on demand, according to a new case report — a feat that was previously thought to be impossible.

In a dark environment, the muscles dilate or enlarge the pupils to allow more light to enter, and constricts them in a bright environment to limit the light flow, a process believed to be completely automatic, and unable to be consciously controlled, Live Science explained.

“Pupils can also change size in response to other factors, such as increases in arousal.”

Christoph Strauch, senior author of the new case report and an assistant professor in the experimental psychology department at Utrecht University in the Netherlands, explained researchers already knew that “by using indirect methods” such as thoughts some people can change their pupil size at will.

“Thinking about the sun could constrict the pupils and that thinking of a dark room or mentally calculating something could dilate them,” Strauch said.

The ability to change pupil size by “directly controlling it like a muscle” was never thought possible. Then a psychology student at Ulm University in Germany reportedly contacted Strauch after taking one of his courses.

The student, who was identified in the case report by his initials, D.W., told Strauch and his colleagues at Ulm University he realized he could change his pupils’ size at about the age of 15 or 16 after he “played computer games for long periods of time.”

“Constricting the pupil feels like gripping, tensing something; making it larger feels like fully releasing, relaxing the eye,” D.W. told the researchers.

Initially, he would do it by focusing in front of or behind an object, but with practice, he was able to do it without focusing on objects. He explained to researchers, “to change his pupil size, all he has to do is concentrate on the eye; he doesn’t have to imagine a bright or dark environment.”

That is what sets D.W. apart from other people who are able to change their pupil size, Strauch told Live Science. That he can feel the muscles in the pupils directly “is astonishing, as it was thought to be impossible.”

Through a series of tests, researchers found no indication that D.W. was changing the size of his pupils indirectly, Live Science reported.

Strauch said if more people can be found who have this ability, researching them might help the team “understand whether there’s a strategy for training people to control their pupil size at will.” Readers who think they may have this ability can reach out to the researchers at [email protected]

The team’s findings were published online on Aug. 12 in the International Journal of Psychophysiology.

Source: Live Science

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