What is "good for one's brain" (apart from proper nutrition and absence of concussions) is a strong education and healthy lifelong social interactions. Human language is essential for these interactions. Having multiple human languages opens more books, interactions, and cultures.
The opposite is to remain closed. This is a dangerous state of mind and culture.
From TFA:
all these studies take for granted the uncontroversial mental superpower that you get from language study: being able to talk to people you could not have otherwise.
Not just to talk to people, but to unlock an understanding of their culture and perspectives.
Talking to more people in more contexts is a practical affordance: having more tools in the shop means being able to handle new and different types of problems effectively. People solve problems working together with people.
Having the cognitive adaptability to use new and different tools is certainly a valuable quality. We can nurture it as a learning objective, but it may may not be as universalisable as we have hoped. That said, the cost of not trying to educate people is to fail even worse.
I don't think I agree that social interactions are necessary to keep one sharp. In fact excessive social interactions with people that aren't all that sharp might dull one a bit.
Reading and thinking and studying can be done alone just fine.
Now as far as effectiveness in the real world, yes, social interactions and fluency is needed, but I believe this to be different from being "sharp". It probably helps keep you looking sharp though.
As someone content with being by myself, I get what you're saying but overall I don't agree. COVID was a good experiment and it busted up a lot of people.
Even excepting COVID, in the elderly the difference with social isolation can be night and day. I have witnessed firsthand one's cognitive deterioration reversed when the person moved into an assisted living community and gained a social life, and then when COVID hit and everyone was locked down the decay set in again
> What is "good for one's brain" (apart from proper nutrition and absence of concussions) is a strong education and healthy lifelong social interactions
Sure, but I think this is more about the fact that what you don't use, you lose. Learning languages is hard, so even learning old Greek keeps you brain sharp as long as you enjoy it to some extent.
Gym for the brain is good, what you do with it can be better, but gym is still good.
The opposite is to remain closed. This is a dangerous state of mind and culture.
From TFA:
Not just to talk to people, but to unlock an understanding of their culture and perspectives.Talking to more people in more contexts is a practical affordance: having more tools in the shop means being able to handle new and different types of problems effectively. People solve problems working together with people.
Having the cognitive adaptability to use new and different tools is certainly a valuable quality. We can nurture it as a learning objective, but it may may not be as universalisable as we have hoped. That said, the cost of not trying to educate people is to fail even worse.