Scientists like to measure natural language against dementia probably because its easier to do then some other form of knowledge (like being good in multiple disciplines).
From the practical standpoint, learning more then 1 one language doesn't make any sense - practical value you get from it is next to 0 compared to for example learning medicine, electronics, IT, math etc.
Especially because it requires the same amount of time.
> From the practical standpoint, learning more then 1 one language doesn't make any sense - practical value you get from it is next to 0 compared to for example learning medicine, electronics, IT, math etc.
That may be true if you're living in a country where English is the main language, otherwise adding English has a lot of practical value.
Or, if you're not a native English speaker who moves to another country where English is not the main language then adding that language tend to have a lot of practical value.
> [...] practical value you get from it is next to 0 compared to for example learning medicine, electronics, IT, math etc.
Source missing. Seriously though, you sound very certain of your claim so let me at least offer a counterpoint, however anecdotal.
I've had tons of practical value out of some of my language skills. I would not have the career I have today if I hadn't learned English as a second language. Admittedly my third language, German, was a bust, but I blame the way schools teach language for that (grammar, grammar, grammar). My fourth language, Thai, OTOH was a great investment not only because it made it possible for me to be self-sufficient and socialize (and make friends) while living in Thailand, it also was so different from the previous languages I knew that I could feel my mind expanding. Finally, I've also cracked my head at (Mandarin) Chinese but in that case the practical value has been much closer to 0 but it at least made it possible for me to travel around China on my own, which was well worth it at the time for me.
