Abstract

Lexical ambiguity has classically been categorized into two kinds. Homonyms are single word forms that map to multiple, unrelated meanings (e.g., “bat” meaning baseball equipment or a flying mammal). Polysemes are single word forms that map to multiple, related senses (e.g., “breakfast” meaning a plate of food or an event). Yet there is a longstanding debate as to whether polysemy and homonymy reflect distinct cognitive representations. Some (e.g., Fodor & Lepore, 2002; Klein & Murphy, 2001) posit that they do not — merely describing differing patterns of usage — while others (e.g., Falkum & Vicente, 2015; Pietroski, 2018) argue that polysemes, but not homonyms, involve an underspecified representation that is neutral with respect to the form’s multiple senses. While some extant experimental evidence supports the latter view (Klepousniotou, Titone, & Romero, 2008; Srinivasan, Berner, & Rabagliati, 2019), there has not yet been clear evidence of the representation of lexical ambiguity affecting domain-general reasoning. Using a novel inference paradigm, we compare participants’ dispositions to endorse deductive, Aristotelian arguments with equivocating polysemes versus comparable arguments with equivocating homonyms. We find that participants endorse the former substantially more than the latter, a phenomenon that we dub the "Uncommon Sense Effect". Our results provide direct evidence that polysemes and homonyms have underlyingly distinct mental representations — in particular that polysemes uniquely invoke an underspecified representation that allows for rule-based inferences across distinct senses.