Conditional inference and access to alternatives: The role of QUD and speaker knowledge in conditional perfection

Conditional statements often imply meanings that extend beyond their literal content, influenced by contextual factors such as the Question Under Discussion (QUD) and a speaker’s epistemic state. One such inference is Conditional Perfection (CP), wherein a statement like, “If p then q,” is strengthened to imply that the antecedent p is the only contextually salient condition under which the consequent q holds (e.g., “p if and only if q”). While previous research has debated the role of QUDs in CP, the role of speaker knowledge has yet to be systematically tested. In two experiments, we investigated how these contextual factors influence conditional reasoning. In Experiment 1, participants were more likely to derive CP when the conditional statement was an answer to a QUD that focused on the antecedent compared to those that were answers to either a neutral QUD or one that focused on the consequent. In Experiment 2, CP was more likely when the speaker was knowledgeable about all alternative antecedents than when they had partial knowledge. These findings support the view that CP arises through a process of exhaustification, wherein the conditional statement is strengthened by negating relevant alternatives. More broadly, they suggest that conditional inferences depend on reasoning about alternative utterances, paralleling other forms of pragmatic enrichment such as scalar implicatures.