In a noisy room, an older person often asks you to repeat yourself. It's not just about the ears. The brain has to snatch the right words out of the general hum, the way a fisherman snatches a single fish from a school. With age, this job gets harder, and if memory and thinking weaken, the difficulties pile up faster.
Scientists tested 446 people aged 45 to 90. Each one listened to words in noise, took a short test of memory and attention, and then lay down in a scanner. It turned out that in people with weaker test results, the ability to distinguish words in noise fell noticeably more steeply with age. By age 80, they needed noise nearly twice as quiet to make out the same words.
If the cable is damaged, the signal arrives with interference. In silence this is almost unnoticeable, but in noise the word falls apart. That's why a simple test of word intelligibility in noise can tell a doctor that a person is starting to have problems not only with hearing but also with memory.
The density of white matter in the brainstem auditory pathways turned out to be higher in the right hemisphere, while in the arcuate fasciculus it was higher in the left. Such mirror asymmetry within a single sensory system had not been described before.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.