Sometimes when an individual has a hard time hearing, someone close to them insultingly says they have “selective hearing”. When your mother used to accuse you of having “selective hearing,” she was suggesting that you paid attention to the part about chocolate cake for dessert and (maybe deliberately) disregarded the bit about doing your chores.
But in reality it takes an amazing act of teamwork between your brain and your ears to have selective hearing.
The Difficulty Of Trying to Hear in a Crowd
Maybe you’ve encountered this situation before: you’ve had a long day at work, but your friends all insist on meeting up for dinner. And of course, they want to go to the loudest restaurant (because they have great food and live entertainment). And you strain and struggle to understand the conversation for over an hour and a half.
But it’s very difficult and exhausting. And it’s a sign of hearing loss.
Maybe, you rationalize, the restaurant was just too loud. But… everyone else seemed to be having a fine go of it. It seemed like you were the only one having trouble. Which makes you think: what is it about the packed room, the cacophony of voices all struggling to be heard, that throws hearing-impaired ears for a loop? It seems like hearing well in a crowd is the first thing to go, but why? The answer, as reported by scientists, is selective hearing.
How Does Selective Hearing Function?
The phrase “selective hearing” is a task that doesn’t even happen in the ears and is formally called “hierarchical encoding”. This process nearly exclusively takes place in your brain. At least, that’s in line with a new study carried out by a team from Columbia University.
Ears work just like a funnel as scientists have known for quite a while: they collect all the signals and then forward the raw information to your brain. In the auditory cortex the real work is then accomplished. That’s the part of your gray matter that handles all those impulses, interpreting impressions of moving air into perceptible sounds.
Because of significant research with CT and MRI scans, scientists have known for years that the auditory cortex plays a considerable role in hearing, but they were stumped when it came to what those processes really look like. Thanks to some novel research methods including participants with epilepsy, scientists at Columbia were able to find out more about how the auditory cortex works in terms of discerning voices in a crowd.
The Hearing Hierarchy
And here’s what these intrepid scientists discovered: most of the work done by the auditory cortex to isolate particular voices is accomplished by two separate regions. They’re what enables you to separate and intensify distinct voices in noisy situations.
- Superior temporal gyrus (STG): At some point your brain needs to make some value based decisions and this happens in the STG once it receives the voices that were previously separated by the HG. The superior temporal gyrus figures out which voices you want to pay attention to and which can be securely moved to the background.
- Heschl’s gyrus (HG): The first sorting phase is handled by this part of the auditory cortex. Researchers discovered that the Heschl’s gyrus (we’re just going to call it HG from now on) was processing each individual voice, separating them into unique identities.
When you have hearing loss, your ears are lacking certain wavelengths so it’s more difficult for your brain to distinguish voices (low or high, depending on your hearing loss). Your brain can’t assign separate identities to each voice because it doesn’t have enough data. It all blurs together as a result (which makes discussions tough to follow).
New Science = New Algorithm
It’s common for hearing aids to have features that make it less difficult to hear in a crowd. But hearing aid manufacturers can now integrate more of those natural functions into their algorithms because they have a better concept of what the process looks like. For instance, hearing aids that do more to distinguish voices can assist the Heschl’s gyrus a little bit, leading to a better capacity for you to understand what your coworkers are talking about in that loud restaurant.
The more we discover about how the brain works, specifically in connection with the ears, the better new technology will be capable of mimicking what happens in nature. And that can result in improved hearing success. That way, you can concentrate a little less on struggling to hear and a little more on enjoying yourself.