A German Student Can Change Pupil Size on Demand

Previously it was thought that enlarging and shrinking or simply to change pupil size on demand is an impossible thing to do until a 23-year-old student of psychology in Germany proved it wrong by doing it as per his will. Yeah, you read that right he can change his pupil voluntarily, a crazy feat right!

As many of us know, the two small muscles in each person’s eye work as the puppet of each pupil which dilates or enlarges itself in the dark so that more light can get in. And opposite to this when the pupil shrinks in bright light so that it can restrict the extra incoming light. The process automatically happens when you move from bright to dark light or vice versa. There are other causes as per which pupils change their size like imaginations and shifts of attention.

Earlier people by using indirect methods can change the size of their pupils but in this case and probably the first time a person is able to do it on will/demand. Christof Strauch, assistant professor in the experimental psychology department at Utrecht University in the Netherlands, and lead author of the study published in the International Journal of Psychophysiology says, “Researchers knew that just visualizing sun can shrink the pupils and thinking about a dark room or mentally calculating something causes its dilation.”

But it was not even imagined that it is possible to change pupil size by controlling it like muscle until a student of psychology at Ulm University in Germany contacted Strauch after taking one of his courses. Earlier when he was around 15 years of age the young man was traced in the case by his initials. As D.W firstly realized that he can change his pupil’s size.

D.W. can change pupil size on demand
D.W.’s eye in different stages of dilation (Eberhardt et al., IJP, 2021)

D.W told researchers that, “Constructing the pupil feels like gripping and then tensing something makes it larger and it brings full relaxation in the eye”. Initially, he changed the size of his pupil by focusing in front of behind an object, but after constant practice, he was able to do it without doing this. He also mentioned to researchers that to bring change in pupil size, he only needs to get concentration on the eye and he doesn’t need to visualize bright or dark environments.

Strauch told Live Science, “That makes D.W different from other people who presented the ability to change their pupil size.” After a number of tests, researchers said that D.W owns this ability and they have not come across any use of indirect methods to change pupil size. In one of the tests, researchers measured the electrical features of the skin by putting voltage to test whether he was stimulated by increased mental efforts which may increase pupils size indirectly.

Naturally, D.W’s pupil dilation ranges up to 0.09inches in diameter and constriction up to 0.03 inches in diameter. By the use of fMRI (functional magnetic resonance imaging), a brain test in which researchers found increased activation of specific parts of the brain that are involved in the violation or can be said as the ability to decide and to go for something with free will.

Researchers are still not sure whether D.W was directly controlling his pupils but in their tests, they did not come across any sign that he was using indirect methods.


  1. I can do the same thing but no one ever believed me…. I told my parents and my best friend too. But they said it’s impossible to change the size of eye pupils on our own will…. And after all this year science is accepting that….


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