[TangoTrotFox]

Chess seems to show the opposite. In particular speak with literally just about any older grandmaster and you'll invariably find their mental faculties are still in great shape. Of course there's always a correlation != causation problem that plagues all sort of social studies. This observation does not necessarily mean that becoming a grandmaster would slow mental decline. It could simply be something within the individuals that drives them to become grandmasters that itself is what staves off the decline.

Ultimately I'm not entirely sure what the point of science along these lines even is. The big risk is you notice a correlation to something and assume causation. You then start working to try to pursue that end in cases where the correlation is good - or avoid that end in cases where the correlation is bad. And you spend immense energy and resources doing this, only to find that in the end there was no actual causation at all and you just spent immense amounts of time, energy, and resources doing nothing.

Even worse is that sometimes you might pursue the correlation and falsely end up at the desired end thus assuming causality when none exists. Maybe the best example of this is human/animal sacrifice of ancient civilizations. Those sacrifices were not baseless from their perspective. What undoubtedly happened is that at one point a civilization has e.g. a bad harvest. They feel they must have wronged the gods, so they end up sacrificing something. And, completely by coincidence, the next harvest is bountiful. Lo and behold, you now have centuries of human and animal sacrifice in a model where you can ignore any negative outcomes by suggesting it simply means that you didn't sacrifice enough. Keep ramping up the sacrifices and indeed eventually you'll get a good harvest, but it has absolutely nothing to do with the sacrifices you've made.

[gnode]

> It could simply be something within the individuals that drives them to become grandmasters that itself is what staves off the decline.

Or it could just be survival bias. If your mental faculties are in decline, then you would be disinclined to continue competing in chess. I can imagine people would stop competing at that level long before they completely lost their marbles.

[TangoTrotFox]

People generally reach grandmaster when they're very young and I'm not restricting my statement to only those that continue to play in international tournaments. One may retire from high level competitive chess, but people rarely give up the game altogether.