What do children know of grammar? According to this article, perhaps more than you think.
It talks about innate knowledge of nouns and verbs by the time a child turns two. There is a brain response to incorrectly using the nouns and verbs.
Of course they’re not sure what this will mean for language learning yet, but the implications could be interesting. It also says the toddlers aren’t capable of using the words correctly as they know they’re supposed to be used. What if that isn’t true?
I suppose it will take more research to figure that out.