There's a theory that it's not cognitive decline which makes it more difficult for older brains to remember but rather it's that they have more memories to sift through.
I'm reading "Algorithms to Live By" by Brian Christian and Tom Grifiths. As per usual, when reading non-fiction I have a habit of getting side-tracked exploring sub-topics. This time it's caching (a topic linked to sorting, searching, and Time Complexity) and how this relates to neurology.
Caching is a way to get around universal speed limits
Inevitably, the greater the size of a collection, the longer it will take to find in it something specific. Geographic distance plays a role as well. It takes a long time to go to the library, search for a book, and bring it home. It takes no time at all to find one book in a stack of them on your desk.
I was surprised to learn how much of computer science is concerned with this, or rather, with taking frequently needed information from a large container and keeping it handy inside a smaller container... A smaller, easier to use, container is called a cache. When a computer needs something it looks first in a cache, i.e. in RAM, and if it’s missing, that's called a “cache-miss”. In this event, the computer takes the comparatively slow process of looking for the data elsewhere, i.e. in a hard drive or a larger cache. True enough, in computers there are caches within caches. It's caches all the way down.
Whosit - Whatsit
When we humans can’t remember a name (for example) we call this a “brain fart”. Similar to computers, after this lapse, we too will begin the slow process of sifting through our memories to find the object of our query. If this happens enough we begin to diminishingly attribute this to our aging and the deterioration of our brain. Here, the authors of "Algorithms to Live By" point to work done around 2014 by psychologists and linguists (as led by Michael Ramscar).
My birds-eye view is of this research is that it demonstrated knowing more makes recognition take longer. Simulations were modeled as old and young brains by being fed appropriately sized amounts of data.
See... studies have shown that older people tend to have greater vocabulary and know more low-frequency words than younger people as an inevitable consequence of the gradual accumulation of information.
These simulated brains were then analyzed as they were tasked with reading and comprehending. The simulated "older brains" were slower than their younger counterparts. All processing or searching takes time and the "older brains" had more to search within. This brings new meaning to the phrase "the burden of knowledge".
Perhaps we should think of a "brain fart", more forgivingly, as a "cache-miss".
Ramscar: “As we experience sporadic lags trying to remember information we should take heart: the length of delay is partly an indicator of the extent of your experience.”
“A lot of what is currently called decline is simply learning”.
P.S. here's a google talk on Algorithms to Live By.