The manner in which children of diverse cultures and varied circumstances acquire language is extremely uniform. Children of accomplished academics in Cambridge pick up English at the same rate at which children of illiterate farmers in Benin pick up Gbe. They will hit the same milestones at the same age. We also know that a stroke can seriously impair a person's ability to use language, even as their memory and powe…
Do you actually know that? Or are you supposing it because it makes sense? Given what I know about the differences in educational outcomes between socioeconomic groups in the US, I wouldn't be surprised if the rate of language acquisition depended on the number and variety of words that a child hears. It may very well be the case that the child of the Oxbridge academics does pick up language more quickly simply because he or she is exposed to more of it.