Children start in on language in much the same way the world over. Their first fifty words tend to be very similar in content, as are their first word combinations (Slobin 1970; E. V. Clark 1979). But as children learn more about the specific language they are acquiring, the courses they follow diverge more and more (see Slobin 1985b, 1992). Early similarities have generally been attributed to children's reliance on conceptual categories such as agent, action, place, and so on, to provide the basis for meanings to be mapped onto their linguistic forms. Postulating a common cognitive basis for children beginning to use language can provide only part of the story: children also have to discover how their particular language encodes different notions and distinctions, and which of these distinctions have been grammaticalized. This they can only do by attending to the language adults address to them. Acquisition, then,must be a product of both cognitive and social influences.

On the cognitive side, investigators have assumed that all children start with some general, salient, conceptual categories; and that they search first for ways to convey these categories when they begin to attach meanings to words. Such categories are universal and should therefore surface in all early language use. Cognitive development, under this view, provides an opening wedge for getting in to language (Slobin 1985a). On the social side, caretakers (adults or older siblings) talk to young children and thereby provide the linguistic categories and grammatical distinctions pertinent to each language.