Abstract

This study is concerned with the properties of the disjunction operator, or, and the acquisition of these properties by English-speaking children. Previous research has concluded that adult truth conditions for logical connectives are acquired relatively late in the course of language development. With particular reference to disjunction, the results of several studies have led to two claims. First, it has been argued that the full range of truth-conditions associated with inclusive-or is not initially available to children; instead, children are supposed to interpret disjunction using the truth conditions that are associated with exclusive-or (e.g., Beilin and Lust 1975; Braine and Rumain 1981, 1983; Paris 1973). A second, related claim is that even when children respond as if they have access to the complete range of truth conditions, their responses result from the failure to distinguish or from and (Paris, 1973). Different conclusions were reached in recent work by Chierchia, Crain, Guasti and Thornton (1998). The experiments conducted by Chierchia et al. (1998) draw upon a distinction between linguistic contexts. In one type of context, the inclusive-or reading of disjunction is available. By contrast, in another type of context, the exclusive-or reading of disjunction is highly preferred; the truth conditions that are uniquely associated with the inclusive-or reading are eliminated in such contexts due to conversational implicatures. One context that cancels conversational implicatures is called the Prediction Mode by Chierchia et al. (1998). Notice that a prediction like (1) is consistent with different scenarios.