Simplification of disjunctive antecedents

Disjunctive antecedent conditionals (DACs), i.e., sentences of the form “if A or B, C”, are the source of a long-standing puzzle. They are generally felt to be equivalent to the conjunction of their simplifications, “if A, C” and “if B, C”, in accordance with the principle of Simplification of disjunctive antecedents (SDA). However, Lewis’s influential theory of counterfactual conditionals invalidates SDA, as do several prominent theories of indicative conditionals. To explain the strong appeal of this principle, various accounts have recently been proposed: for some, SDA stems from the potential of disjunction to generate semantic alternatives; for others, it arises from a non-Gricean exhaustification operator. To shed light on the status and source of SDA, we administered a picture-based binary forced choice task to 169 children (aged 4;1–9;11) and 28 adults, who were asked to evaluate indicative and counterfactual DACs. Our results reveal that SDA emerges early, being the preferred interpretation already at age four to five. This is in line with the idea that SDA is tightly related to free-choice inferences, which also emerge early (Tieu et al. 2015). We found that subjects who derived SDA in indicatives also derived it in counterfactuals and vice versa, supporting the idea that SDA has the same status in both kinds of conditionals. We did not find any evidence of a shift from a pure Lewisian reading to an SDA reading, which may have supported the exhaustification account. Instead, our data reveal an interesting developmental trend from disjunctive to conjunctive interpretation of DACs, strictly parallel to a trend from existential to universal interpretation of plural definites (Tieu et al. 2019), supporting the idea that SDA involves homogeneity over the antecedent alternatives, as proposed by Santorio (2018) and Cariani & Goldstein (2020). EARLY ACCESS