Children interpret disjunction as conjunction: Consequences for theories of implicature and child development*

We present evidence that preschool children understand disjunctive sentences as if they were conjunctive. The result holds for matrix disjunctions as well as disjunctions embedded under every. At the same time, there is evidence that children understand or as inclusve disjunction in downwardentailing contexts. We propose to explain this pattern of results by assuming that the child knows the inclusive disjunction semantics of or, and that the conjunctive inference is a scalar implicature. We make two assumptions about implicature computation in the child: (i) that the child accesses a proper subset of the adult alternatives (specifically, they do not access the lexicon), and (ii) the child possesses the capacity to strengthen sentences with implicatures, and specifically that they possess the covert exhaustive operator that we assume is responsible for strengthening in the steady state. Under our proposal, the child’s conjunctive strengthening follows from the same mechanism used by the adult to compute free-choice (recursive exhaustification). We furthermore present evidence that children prefer to strengthen disjunctions to conjunctions, in matrix and embedded positions (under every); this mirrors previous findings that the adult prefers to compute free-choice, at the root and under every. We propose a disambiguation strategy that explains the preference for conjunctive strengthening – by both the child and the adult – even though there is no general preference for exhaustification.