Are our brains more prescriptive than our mouths? Experience with dialectal variation in syntax differentially impacts ERPs and behavior.

We investigated online auditory comprehension of dialectal variation in English syntax with event-related potential (ERP) analysis of electroencephalographic data. The syntactic variant under investigation was the double modal, comprising two consecutive auxiliary verbs (e.g., might could). This construction appears across subregional dialects of Southern United States English and expresses indirectness or uncertainty. We compared processing of sentences with attested double modals and single modals in two groups of young adult participants: listeners who were either familiar (Southern) or unfamiliar (Unmarked) with double modal constructions. Both Southern and Unmarked listeners engaged rapid error detection (early anterior negativity) and sentence-level reanalysis (P600) in response to attested double modals, relative to single modals. Offline acceptability and intelligibility judgments reflected dialect familiarity, contrary to the ERP data. We interpret these findings in relation to usage-based and socially weighted theories of language processing, which together capture the effects of frequency and standard language ideology.