Humans

The shape of your ears can actually change the shape of the world around you


We pierce them. Stick Q-tips in them (please don’t). Carelessly subject them to loud music. Sometimes, we even forget to wash behind them.

We may not spend a lot of time thinking about our ears, but we really ought to take better care of them, because they’re essential for making sense of the world around us.

 

In fact, they’re so sensitive and complex, scientists are still figuring out new things about how the ears communicate with the brain – and the awesome limits of that power.

It’s already fairly well understood how the brain performs sound localisation on the horizontal pane, thanks in part to what’s called the interaural time difference (ITD).

The ITD is basically a stereo system, where an infinitesimal but nonetheless perceptible delay – between when sound waves reach your left versus your right ear – tells your brain whether the source of that sound is located on your left or your right.

But what about telling up from down? That’s not so well understood, but a recent study led by neuroscientist Régis Trapeau from the University of Montreal in Canada sheds new light on how we differentiate sounds on the vertical pane.

Sixteen volunteers took turns sitting in a Dyson-Sphere-esque dome of arrayed speakers, with the researchers playing sounds from different points around the dome while observing the participants’ brain activity via fMRI scanners.

The scans revealed that as the source of the sounds became higher, neuron activity reduced. It’s not understood exactly why this is, but the researchers think it could be some kind of evolutionary adaptation to sounds emanating from below us, as opposed to above us.

 

But it turns out that response can be subtly shifted, if the shape of your ear happens to change.

That doesn’t ordinarily happen, but in the experiments, the insertion of thin silicone moulds into the participants’ ears threw off their vertical sound localisation, making them think sounds were emanating from places they weren’t.

“We would put a sound above the participant’s head, and he would say it’s below,” Trapeau told The New York Times.

After a period of time – during which the volunteers kept wearing the moulds – the participants adapted to the new, artificial contours of their outer ears, and got a grip on their vertical orientation again.

But it just goes to show how something as subtle as the shape of our ears radically affects our perception of the world around us.

Pretty weird, but weird doesn’t come close to explaining some of the strangest, still not fully understood things about ear science.

Like what, you might ask?

Like how there’s a mysterious link between smoking and hearing loss, and how one in five people can ‘hear’ things that don’t actually make any sound – a phenomenon called visually-evoked auditory response (aka vEAR).

 

And don’t get us started on how your right ear is likely to be better at hearing than your left at times when your brain is overloaded, or how there’s an unexplained neural relationship between tinnitus and chronic pain.

Clearly ears are weird, but they’re also wonderful, with untapped potential to do things that almost seem like superpowers – such as learning how to mimic animals’ echolocation abilities, detecting the size of a room by nothing more than a tongue click.

It sounds impossible, sure, but other studies are demonstrating the exact same thing.

So look after your ears, because they’re totally amazing. And seriously, quit it with the Q-tips.

The new findings are reported in The Journal of Neuroscience.

 



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