Previous studies involving other brain activities have shown improvement in grey matter before, for e.g. London Taxi driver in one study showed improvement in brain development.
Just a nitpick: Vedic Sanskrit has pitch accent, not tone. Chinese is tonal. And I'm a huge fan of ghana patha as well!
shanti people - tandava (david garry x dion 2017 club edit) https://m.youtube.com/watch?v=8w3R5yEBhcY
shanti people - mahishasura mardini (droplex remix) https://m.youtube.com/watch?v=4em0Wh8ZgR0
it is a ukrainian group i believe, the singer gets very little pronounciation 'off', atleast in these two vids
For about 1000 years before writing starts in India, we have the language developing in the hands of bards singing for ritual reasons to audiences which increasingly could not understand the words. So for many centuries it was evolving under pressures very different from normal language.
Eventually, it regained broader application, but still a an elite language and thus still had unusual evolutionary pressures.
My email is in my profile if you'd prefer to tell me more about this offline.
Another interesting note is that Vedic mantras are sometimes traditionally learnt and recited in what is known as a Ghana patha. If i were to number the words in a sentence, “The cow jumped over the moon” as 1 2 3 4 5 6 and then if I were to recite the sentence now permuting the words as 1 2 2 1 1 2 3 3 2 1 1 2 3,, 2 3 3 2 2 3 4 4 3 2 2 3 4.... The complexity increases. This is because words can be joined together in Sanskrit. Furthermore each letter in Vedic Sanskrit has three ways of pronouncing it (similar to the Chinese four accents) and these can change as you permute and apply the sandhi rules as well.
I haven’t seen such complexity in other languages (though it’s possible it may exist) but such complexity is why it wouldn’t surprise me that the effect could possibly be specific to Sanskrit.