About the reasons for such trend, it rejects the perception that brain cells are lost with age, and writes,
"What is stuffed into your head may not have vanished but has simply been squirreled away in the folds of your neurons... Neural connections, which receive, process and transmit information, can weaken with disuse or age... (However) if you are primed with sounds that are close to those you’re trying to remember... suddenly the lost name will pop into mind. The similarity in sounds can jump-start a limp brain connection... The brain, as it traverses middle age, gets better at recognizing the central idea, the big picture. If kept in good shape, the brain can continue to build pathways that help its owner recognize patterns and, as a consequence, see significance and even solutions much faster than a young person can."
How do we keep brain connections in good condition and to grow more of them?
"For adults, one way to nudge neurons in the right direction is to challenge the very assumptions they have worked so hard to accumulate while young. With a brain already full of well-connected pathways, adult learners should 'jiggle their synapses a bit' by confronting thoughts that are contrary to their own... continued brain development and a richer form of learning may require that you 'bump up against people and ideas' that are different. In a history class, that might mean reading multiple viewpoints, and then prying open brain networks by reflecting on how what was learned has changed your view of the world...
If you always hang around with those you agree with and read things that agree with what you already know, you’re not going to wrestle with your established brain connections... get out of the comfort zone to push and nourish your brain... As adults we have these well-trodden paths in our synapses... We have to crack the cognitive egg and scramble it up. And if you learn something this way, when you think of it again you’ll have an overlay of complexity you didn’t have before — and help your brain keep developing as well."