Most of you don’t yet have this to worry about, but here it is—
As adults without any neurological disease get older, the grammatical complexity of their sentences declines (people in their twenties use an average of 3 clauses per sentence; people in their seventies average about 1.4). The density of propositional content in their sentences declines, as do word-finding abilities (which explains, by the way, Trump’s restricted repertoire of, say, adjectives: “horrible,” “terrific,” “great,” “big,” “nice”). In studies of the coherence of a discourse, the older talkers are less able to stay on topic, even though sentence to sentence remain connected to each other. However, older speakers produce more coherent discourse when they’re talking with younger people — as Trump often is. The younger speaker — or the interviewer — “appears to scaffold the performance of their elderly partner by introducing ideas and phrases that can then be developed by the elderly individual,” wrote Lauren Saling and others in a 2014 research articlein The Journal of Gerontology.
Michael Erard via The Awl
(Michael Erard has been mentioned here before.)