New research on the shape of the human ear reveals a masterful design. A paper published Monday in the Journal of Neuroscience explains that the brain learns the ridges of the outer ear, and uses that information to pinpoint the location of sounds. When researchers filled in an external part of volunteers’ ears with silicone, it drastically changed their ability to tell the height of a sound.
Scientists already understood how the brain detects whether a sound comes from one side or the other based on whether it reaches the right or left ear first. But they weren’t sure how the brain determines the height of a sound. It turns out, our brains decide if a sound is high or low—like whether a missing cell phone is ringing from atop a bookshelf or under the couch—based on how the sound waves bounce off the outer parts of the ear.
When the researchers fitted participants with a small piece of silicon in their ears, changing their natural ridge patterns, their hearing suffered.
“We would put a sound above the participant’s head, and he would say it’s below,” Regis Trapeau, a neuroscientist at the University of Montreal and the author of the new paper, told The New York Times.
But remarkably, after a week of wearing the silicon insert, the volunteers’ brains learned the new ridges of their ears, adapted to the change, and could correctly locate sound again. —Kiley Crossland