Your Brain Plays a Cool Trick to Help You Hear in Noisy Places

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Silence may be good for the brain, but it’s not often that you experience it for any extended period of time — life, especially city life, is generally pretty noisy. Think about it: When’s the last time you had a conversation with another person where your two voices were the only noise in the room? More often, you’re talking over all the traffic going by, or the chatter of all the people around you, or any of the other ambient sounds that make up the auditory landscape of an average day.

Which, of course, means the odds are good that you’ll miss some stuff — the person you’re talking to is mid-sentence when a car honks, maybe, or someone yells into their phone. Luckily, most noisy distractions aren’t enough to prevent you from following along: “The brain has evolved a way to overcome interruptions that happen in the real world,” Matthew Leonard, a neurology researcher at the University of California, San Francisco, recently told New Scientist. When your ears fail to pick up on a word, your brain is pretty good at filling in the gap, a phenomenon that scientists call “perceptual restoration.”

And in a study recently published in the journal Nature Communications, Leonard and his colleagues shed some light on exactly how that works. The study authors recruited volunteers who had previously had electrodes inserted into their brains (a way of managing epilepsy) and used them to measure the participants’ brain activity during the experiment. New Scientist explained:

The team played the volunteers recordings of a word that could either be “faster” or “factor,” with the middle sound replaced by noise. Data from the electrodes showed that their brains responded as if they had actually heard the missing “s” or “c” sound.

This seems to be because one region of the brain, called the inferior frontal cortex, predicts what word someone is likely to hear – and it does this two-tenths of a second before the superior temporal gyrus starts processing the sounds a person has heard.

In other words, you’re not actually hearing a chunk of what you think you are — but the cool part is that it doesn’t really matter either way.

Your Brain Plays a Trick to Help You Hear in Noisy Places