I mean, given that GMs or other strong players (I choose strong players because their peak rating vs low has "more data" than that of weaker players but it probably relates to weaker players also) decline in strength, can anything about that decline be predicted by their ascension?
For example, would the rate of Elo decline have anything to do with rate of the increase? (assuming no rating floor as with USCF ratings)
Or would the computer measurement of accuracy decline as it had increased?
I suspect there is no such simple relationship -- it is not symmetrical. But I wonder if neuroscientists or cognitive psychologists could use chess as a way of predicting general cognitive decline or even helping mitigate it -- maybe show individuals what to expect and ways to compensate for it by preparing for it with specific exercises.
I am by the way guessing increase is much sharper curve than decrease -- perhaps even the sharper the increase (indicating more native talent or whatever) the smoother and slower the decline.
I think chess and probably other skill games where computers display far-above-human ability are uniquely suited for getting a general picture of cognitive ability whereas IQ tests can simply be taken so many times that they become useless for genuine assessment.
However, other types of objective mental tests like short-term memory and reaction time would be interesting to juxtapose with this kind of chess testing.
Edit: It does not have to be a positive correlation; it could be the faster the ascension the slower the decline. I recall reading the earlier one took up chess the longer skills were retained which sounds reasonable. Reshevsky played good chess well into his 70s and he of course was a famous prodigy. Capablanca also was one but he died relatively young. Morphy same situation. Karpov learned from just watching at also a young age (I think learning without being taught the moves as a toddler is always a good sign and all these guys did it while the rest of us don't have a firm grasp on en passant even after it is explained) and remains a grandmaster-strength player.
EDIT: I meant to ask mainly about the way the brain works as it ages and whether chess can help predict how the brain will work in other areas. This is not meant to be a question about why people get into chess or why they leave it. It is about players who continue to play for potentially years beyond their peak and what happens to the rating of an active player as measured by computer as well as ELO -- when a player starts losing ELO, what aspects of his game suffer, what remain stable and maybe even improve as they age and how rating increase patterns might predict decline. Note that even if a sharp increase tends to be followed by a slow decline, this is a kind of relationship between the two patterns: I do not think a sharp increase growing up predicts and equally sharp decline, quite the opposite. In languages, the earlier the language is learned the better it is retained and I think that I read chess works the same way: former child prodigies play better chess in old age than players who started in their teens, even if at some point both the former prodigy and the "late bloomer" were equals: I think the latter will find that he starts to lose understanding of concepts that are intuitive to the ex-prodigy. And if it does not work that way, that is really interesting although profoundly unlikely that somehow starting late somehow is better for chess long-term -- I suspect zero evidence for that although each player is his own special case.
Here is a story that is tangentially related. An aged physicist had stopped being able to communicate but when another physicist visited her, instead of talking in English to her (which was her adopted second language) he spoke to her in her first language, German and she was able to converse well. One might have thought, Well, she learned and spoke English more recently, so this should be her best current language, but not so at all. This is also like an old person saying, I can't remember what I had for lunch but I recall my childhood like it was yesterday.
So again, learning chess at 3 or 4 is probably a huge advantage. We note also that the best Polgar sister was the youngest and I can think of other cases where the younger of two siblings far outstrips the older in chess. Or fathers who make master but their sons make GM. It is having the advantage that the father did not have, a master player to learn from.
I also have noticed in the case of siblings that the older sibling finds the difference in strength to be a very touchy subject.