When OR is assigned a conjunctive inference in child language

It has been proposed that children differ from adults in that children license a conjunctive inference to disjunctive sentences that lack any licensing expression. The proposal is that children infer “A and B” from sentences of the form “A or B.” Although children’s conjunctive interpretations of disjunction have been reported in some studies, they have not been observed in other studies. This study investigates one possible source of the different findings, which is the presence or absence of objects that are contextually introduced, beyond those mentioned in the test sentences. Using a Truth Value Judgment Task, we conducted three experiments with preschool Mandarin-speaking children and a control group of adults. Test sentences in Experiment 1 included disjunction and a deontic modal verb, and the contexts only included objects that were mentioned in the test sentences. In Experiment 2, the deontic modal verb was omitted from the test sentences. Experiment 3 presented the same sentences as Experiment 2, but the contexts included additional objects beyond those mentioned in the test sentences. Both children and adults assigned a conjunctive inference to the test sentences in Experiment 1. In Experiment 2, with no deontic verbs and no contextually introduced objects, a subset of children computed conjunctive inferences, whereas none of the adults did. In Experiment 3, neither group made a conjunctive inference. The findings reveal that entities in nonlinguistic contexts influence children’s understanding of logical expressions. Moreover, preschool children already have linguistic knowledge that modal verbs license conjunctive inferences for sentences with disjunction.