The reason why older people typically can’t hear very well has very little to do with the functional capabilities of their ears, Co.Exist reports. Instead, as a recent study in the Journal of Neurophysiology (freely available here) investigates, it has more to do with how the brain processes sound, and how that ability deteriorates as we age.
Researchers at the University of Maryland, College Park report that the deterioration is due to aging’s effect on the brain’s midbrain (associated with hearing as well as vision and motor control) and cortex (associated with thought and language). The study examined 17 younger adults and 15 older people with no signs of dementia. They were asked to listen to an audiobook while another narrated audiobook played in the background.
When trying to distinguish between the voices of two different speakers, the midbrains of older adults don't respond as strongly as those of younger people. The older adults' brains couldn’t encode the auditory signals as well, and they took longer to process speech, especially when there were two competing voices. The older brain appears to be less capable of picking out one sound out of many.
However, their cortex actually reconstructed the amplitude of the speech they heard in the brain with greater accuracy—an exaggerated response, which may reveal why older people need to pay more attention to process the noise of people talking. As the study's abstract notes, this response suggests "an age-related over (or inefficient) use of cognitive resources that may explain their difficulty in processing speech targets while trying to ignore interfering noise."
So the next time you encounter an older individual who is hard of hearing, don’t bother trying to speak louder. It won’t help them hear you any better. Instead, move your conversation to a place with less background noise.
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