Observation 1.
My 8-year-old frequently says things like, "John, he was playing basketball," topicalizing the subject by left-dislocating it. (I'm not sure if this is only for animates.) This is not usual in our dialect, so I doubt that the kid has often heard it. My wife and I incessantly correct this usage (yes, yes, intellectually I am a good descriptivist, practically, however...), and yet it persists strongly.
This is rather interesting, I think.
To the best of my (limited) understanding, most syntactic formalisms are structured around subject-predicate relations, and treat information structure as piggy-backing on fundamental mechanisms, but this observation makes me wonder if information structure might be more fundamental in some sense.
Observation 2.
Observation of my (slightly language delayed) not-yet-two-year-old leads me to consider further a foundational role for attention and indexicals. (I know the latter is a rather old idea.)
The child has excellent comprehension, as far as we can tell, as he responds appropriately to quite complex utterances, and makes himself understood (with difficulty) mostly through grunts and gestures (and a slowly growing vocabulary).
What I've noticed, though, is that he achieves communication largely by coordinating and controlling mutual attention. He will gesture so to capture my attention and direct it to an important object, and in fact will often grab my face and turn it to face him as he gestures, or to face what he is interested in, before gesturing and grunting his "utterance".
Much of his speech therapy also uses attention as a key mechanism; vocabulary is given to him as he attends to certain objects in play, or to draw his attention to those objects.
The primacy of vocatives in early speech is also closely related to attention coordination - very simply, a vocative is "getting someone's attention".
Information structure, whether topic, focus, or given/new is also about coordinating attention between the speaker and hearer.
Language development would seem, therefore, to depend critically on elements of theory-of-mind having to do with (at least) attentive focus (and related notions such as affordances and intentions). Notions such as "reference" would thus be constructed socially, in a sense, by mutual attentive connection of a linguistic unit and the referent.
(I think the notion of mutual attentive focus largely solves Quine's "gavagai" conundrum.)
Please forgive me if these musings are old-hat, utterly naïve, or just plain stupid. But if you are better informed about these matters, please comment with some relevant reading...
