| in Interesting Facts Human Body
Only one person is known to be able to voluntarily change the size of their pupil.
There are many things going on in our bodies over which we have no control. For example, most of us cannot control the size of our pupils unless we change the amount of light that enters our eyes. Researchers observed a man who can apparently change the size of his pupil on command in a study published in the International Journal of Psychophysiology in 2021. Currently, he is the only person known to be capable of doing so—though you could give it a shot if you wanted!