Physical activity is the clear winner just from an overall impact perspective, but you don't need much to reap the benefits, so there's plenty of time for other

Physical activity is the clear winner just from an overall impact perspective, but you don't need much to reap the benefits, so there's plenty of time for other stuff. Beyond that, I'd say learning an instrument is probably a better investment than learning a language unless you need to learn the second language to live somewhere. This is because: - language learning takes a LOT of time investment to show utility compared to using a translate app, while a lot of instruments are fun to play stuff on even when you suck - Music is also a language, but it's a language of tonal relationships and how they map to emotion, and the emotional phrases they can form, which is more distinct than another spoken language. - Learning an instrument also forces heavy bidirectional communication between brain hemispheres. Normally humans are very "one half brain then the other" so this encourages more plasticity. Puzzles have been shown to be poor for cognitive development unless they closely model the cognitive task being measured, so don't bother unless you just really like puzzles.