Here is more about the “quality of input” and vocabulary acquisition matter (see here). Our group has studied this topic (See our paper published in PNAS, 2013, not connected to the recent Hirsh-Pasek study; the link for this is here). So I want to correct the mangled NYTimes article that has generated so much interest and perhaps will even influence educational policy in future. First, some facts: Hirsh-Pasek, whose work/speech at the White House this newspaper article reports, did not specifically look at possible differences in “quality” (of which, more below) that might vary as a function of class, wealth, etc. All her subject learners were of lower class SES, and so could shed no light on whether or the extent to which “quality input” is unequally distributed across SES classes, because she had no comparison group (i.e., learners from other than low SES strata). Yet the implication was left hanging in the NYT air, just by mentioning that these children were all lower class, that wealthier people provide classier “communicative foundations” to their offspring. Our own study does in fact make this SES comparison directly, and the bottom line is that there is no measureable difference in “quality of input,” if we can define such a thing at all, as a function of social class. So either ignore what you read in the NYT, or go read our article and see what you think in the light of the evidence we presented. There is an SES-linked difference in the quantity of speech (sheer number of words) infants hear before the 5th birthday, however.
But now back to what “quality of input” could be, in any sense relevant to facilitative environments for language learning. The Hirsh-Pasek study isn’t published as yet, as far as I know, but her “White Paper” summary suggests that she “coded” maternal speech and behavior for the extent to which it is “symbol infused,” and related categories that are, perhaps themselves hard to understand or apply generally. Despite the real difficulties of such hand coding over highly variable naturalistic interactions, there are some facts about nonlinguistic environmental variance in relevant regards that are strong enough to shine through. Specifically, as our studies showed, there is a very powerful influence of referential transparency (that’s what “quality” largely comes down to, when you peel away abstract labels like “foundations of communication” that appear in this literature). Referential transparency is simply your good-old commonsensical notion: there are times, during conversational interaction, when a listener is attentionally focused on a particular thing, action, etc., and the speaker via gesture, manipulation of the object, gazing/pointing at it, also mentions it. A blatant case (pace Quine) is saying “This is a squirrel” while pointing to and gazing at a squirrel in the presence of child’s close attention to a squirrel. Turns out that there are stable, measurable, and strikingly large familial differences in the proportion of time that such informative extralinguistic contexts are provided to infants (as I said, their presence/frequency unrelated to the wealth or class of the family), and these differences (already observed in our sample populations at child age 14 months) predict vocabulary size when measured 3 years later as these children enter kindergarten. Colin in an earlier blog ably described why this very large early vocabulary-size difference matters, over the longer run, in the Real World of school and future job, so I won’t belabor that point. But a few words now on the lexicon and whether it has any linguistic interest.
Of course it does. As has been evident since the seminal work of Carol Chomsky on ask/tell/promise/easy/eager, the business of acquiring the language-specific grammar is inextricably (I hate that word, but it’s right here) tied up with acquiring the meanings of terms whose interpretation is not so transparent to referential observation as is, say, “cat.” For instance, imagine a blind child acquiring “look” and “see.” Or anyone trying to acquire “think.” This can’t be done if the input is solely referentially consistent cases, i.e., everyday scenarios in which thinkers are thinking, but requires in addition (or even instead) access to predicate-specific licensed syntactic structures. The issues here are not only relevant but pretty central to linguistic theorizing, in my opinion (see the huge literature on “syntactic bootstrapping”). But how about “cat”? After all, learning must begin with such homely cases, for which referential information provides the bulk of the basis for identification. They begin to be understood as early as the 6th month of life. These words provide the scaffolding for at least rudimentary acquisition of the grammar (mainly: where, structurally speaking, is the sentential subject in the exposure language) so their acquisition function is of some preliminary interest for linguistic-developmental theorizing. This first lexical stock forms crucial grounding information, the first step to enable all the later fancy footwork, i.e., the gateway to the linguistic-computational achievements that can then – and therefore – proceed. I hastily remind that how the concepts themselves (not the words for them) are acquired is an abiding mystery, but one that necessarily is engaged outside Linguistics, notably by people who study perceptual development, theory of mind, and the like (see, e.g., important lines of research from from Spelke; Csibra, and many others).