Listeners expect grammatical variation across dialects.

Dialect variation is universally attested among languages, yet the cognitive processes underlying listeners' adaptations to different dialects, particularly in morphosyntactic variation, remain underexplored. This article investigates how listeners represent and adapt to their interlocutor's dialect based on their linguistic experience, examining monodialectal speakers of Dominant American English and bidialectal speakers of Dominant American English and African American Language. In Experiment 1, participants rated written sentences to indicate the likelihood that a speaker of a given dialect would say them. All participants demonstrated knowledge of African American Language's regularized subject-verb agreement rules, rating sentences like "They was happy" as more likely than "He were happy." However, bidialectal participants showed greater differentiation between the sentences than monodialectal participants. This finding suggests that listeners do not simply relax grammatical expectations when exposed to linguistic diversity; rather, they form specific expectations of a dialect's grammatical rules. In Experiment 2, we tested whether these expectations influence perception. Participants transcribed sentences where agreement was acoustically ambiguous ("She sit[s] still"). Participants were more likely to transcribe regularized subject-verb agreement ("She sit still") when listening to an African American Language speaker compared to a Dominant American English speaker, regardless of their linguistic experience. Bidialectal participants were more likely to transcribe regularized subject-verb agreement overall. In Experiment 3, we found that such effect patterns were likely driven by morphosyntactic cues, rather than social cues to the race of the speaker. These results suggest that listeners form mental models of others' grammars to guide comprehension, with the precision of these models depending on their linguistic experience. (PsycInfo Database Record (c) 2026 APA, all rights reserved).