The linguistics and psycholinguistics I studied and taught decades ago made me very, very cautious of large propositions about the role of language(s) in forming philosophical or psychological traits or tendencies--particularly those that amount to "X is the language of Y." Philosophcial and psychological positions or profiles or tendencies or whatever one might call them are enormously complex, the resultants of neurochemical and environmental influences, and I view with suspicion any analysis that sees, say, grammar or vocabulary as having great power in their formation.

As for learning multiple languages--I am a strong supporter for language study early on, though I doubt that it makes any neurological difference. I studied Latin and French in high school and college and have lived in and struggled with the languages of Denmark and Italy, but I never became comfortable (for reading or conversation) in any language but English. Nevertheless, I believe my grasp of nuance and my ability to absorb new ideas is the equal of any polyglot of equivalent age and educational level. (I read and write for a living, such as it is.) I learned elementary computer science in my 40s and business journalism and swing guitar in my 50s. I doubt that learning Magyar would improve my miserable mathematical abilities (calculation has always been non-intutive for me). As for fast reading for content versus slower reading for absorption of nuance (which is what I take "classical reading" to indicate), I do both and have done so for fifty-plus years. These are not mutually exclusive skills, and if young people are bad at the latter (which is my wife's experience with her university students) it is the result of lack of practice. Of course, it may be a skill that is best acquired at an early age--there is evidence that lacking early practice, they will never read complex texts with the level of ease and confidence I take for granted. (Though it's hard to disentangle sloth and self-indulgence from whatever disabilities they may suffer.)