Most studies of the cognitive bases of language acquisition are concerned with semantic content: how young children conceptualize the referents of particular linguistic items and expressions. But being able to conceive of all the possible referents another person might intend to indicate is not enough. To acquire the conventional use of a new linguistic item a learner must also be able to identify which of these conceivable referents another person is attempting to single out when using that item in a particular communicative circumstance. This raises issues of social cognition and how young children understand the intentional actions, including communicative actions, of other persons.

The process is never totally straightforward. The philosopher Wittgenstein (1953) noted that even an ostensive definition - the seemingly simplest case of language acquisition in which one person “shows” another what a word means - is problematic because it assumes that both teacher and learner know what “showing”is and precisely how it serves to pick out individual referents in some language-independent way. The point was crystalized by Quine (1960) in his parable of a native who utters the expression “Gavagai!”and “shows” a foreigner the intended referent by pointing out a salient event as it unfolds. One approach to the problem of referential indeterminacy in the study of lexical acquisition is the so-called “constraints” approach (e.g. Markman 1989, 1992; Gleitman 1990). The social-pragmatic approach to the problem of referential indeterminacy takes a very different perspective on lexical acquisition.