On realizing external arguments: a syntactic and implicature theory of the disjointness effect for passives in adult and child grammar

We present an account of why disjoint reference effects obtain in verbal but not in adjectival passives. Passives in child language are independently argued to always be adjectival, which allows us to use a natural experiment in child grammar that is not available in the adult grammar: predicting the lack of a disjoint reference effect in even those passives that prima facie seem verbal. We conduct our discussion against the background of the difference between adjectival and verbal passives in general. Our account is based on (grammatical) Implicature Theory. Since the initiator in the semantic representation of adjectival passives stays at a kind level, it cannot introduce a discourse referent, hence cannot trigger a disjointness implicature, unlike the initiator in verbal passives (Gehrke 2013, 2015). We show in two experiments that children’s passives do not exhibit disjoint reference, unlike adults’ verbal passives, even though children have no trouble computing disjointness implicatures elsewhere. Our contribution thus confirms with a novel kind of evidence the syntactic nature of young children’s difficulty with verbal passives. It offers a new perspective on the external argument difference between verbal and adjectival passives based on Reinhart’s (2016) Theta System, while also offering additional evidence for a grammatical, rather than general pragmatic, theory of implicatures.