Selective hearing is a term that normally gets tossed about as a pejorative, an insult. When your mother used to accuse you of having “selective hearing,” she meant that you listened to the part about chocolate cake for dessert and (maybe intentionally) ignored the part about doing your chores.
But it turns out that selective hearing is quite the skill, an amazing linguistic accomplishment carried out by cooperation between your ears and brain.
Hearing in a Crowd
This situation probably feels familiar: you’ve been through a long day at work, but your buddies all insist on going out to dinner. And of course, they want to go to the loudest restaurant (because it’s trendy and the deep-fried cauliflower is delicious). And you spend an hour and a half straining your ears, trying to follow the conversation.
But it’s very difficult and exhausting. And it’s a sign of hearing loss.
You think, maybe the restaurant was just too loud. But… everyone else appeared to be having a great time. The only person who appeared to be having trouble was you. Which makes you think: what is it about the packed room, the cacophony of voices all battling to be heard, that throws hearing-impaired ears for a loop? It seems as if hearing well in a crowded place is the first thing to go, but why? The answer, as reported by scientists, is selective hearing.
How Does Selective Hearing Operate?
The phrase “selective hearing” is a process that doesn’t even take place in the ears and is technically known as “hierarchical encoding”. Most of this process happens in the brain. At least, that’s as reported by a new study carried out by a team at Columbia University.
Scientists have recognized for quite some time that human ears effectively work as a funnel: they gather all the impulses and then deliver the raw information to your brain. In the auditory cortex the real work is then done. That’s the part of your gray matter that processes all those impulses, interpreting impressions of moving air into recognizable sounds.
Because of significant research with CT and MRI scans, scientists have recognized for years that the auditory cortex plays a significant role in hearing, but they were clueless when it came to what those processes really look like. Scientists were able, by making use of unique research techniques on people with epilepsy, to get a better picture of how the auditory cortex picks out voices in a crowd.
The Hierarchy of Hearing
And here is what these intrepid scientists discovered: most of the work accomplished by the auditory cortex to isolate specific voices is accomplished by two different regions. They’re what allows you to separate and intensify distinct voices in loud settings.
- Heschl’s gyrus (HG): The first sorting stage is handled by this region of the auditory cortex. Heschl’s gyrus or HG processes each unique voice and separates them into distinguishable identities.
- Superior temporal gyrus (STG): The differentiated voices move from the HG to the STG, and it’s at this point that your brain starts to make some value determinations. Which voices can be comfortably moved to the background and which ones you want to focused on is figured out by the STG..
When you have hearing impairment, your ears are missing specific wavelengths so it’s more difficult for your brain to recognize voices (depending on your hearing loss it might be low or high frequencies). Your brain can’t assign separate identities to each voice because it doesn’t have enough data. Consequently, it all blurs together (which makes conversations hard to follow).
New Science = New Algorithm
It’s standard for hearing aids to have functions that make it less difficult to hear in a crowd. But now that we know what the fundamental process looks like, hearing aid makers can integrate more of those natural functions into their instrument algorithms. As an example, you will have a greater capacity to hear and understand what your coworkers are talking about with hearing aids that assist the Heshl’s gyrus and do a little more to separate voices.
The more we discover about how the brain works, particularly in connection with the ears, the better new technology will be able to mimic what happens in nature. And that can result in improved hearing success. That way, you can concentrate a little less on straining to hear and a little more on enjoying yourself.