Without moving your head, look to your left. Now look to your right. Keep flicking your eyes back and forth, left and right.
Even if you managed to keep the rest of your body completely still, your eyeballs were not the only parts of your head that just moved. Your ears did, too. Specifically, your eardrums—the thin membranes inside each of your ears—wobbled. As your eyes flitted right, both eardrums bulged to the left, one inward and one outward. They then bounced back and forth a few times, before coming to a halt. When you looked left, they bulged to the right, and oscillated again.
These wobbles happen every time you move your eyes, whether or not there's external noise. The bigger the movement, the bigger the wobble. But no one knows why they happen. And until Jennifer Groh, from Duke University, discovered them, no one even knew that they happened at all.
Groh has long been interested in how the brain connects information from our eyes and ears. In a loud party, for example, we automatically read the lips of our conversational partners to interpret any unintelligible sounds. For that to work, the brain has to align visual and auditory information in space, so it knows that those sounds are coming from those lips. And that’s easier said than done, because our ears are obviously fixed on our heads but our eyes are constantly moving. They flit all over the space in front of us, roughly three times a second. Every such movement changes the spatial relationships between what we see and what we hear. So how does the brain unite those streams of information? And where?