The time course of contextual cohort effects in auditory processing of category-ambiguous words: MEG evidence for a single “clash” as noun or verb

Phoebe Gaston, Alec Marantz

The size and probability distribution of a word-form’s cohort of lexical competitors influence auditory processing and can be constrained by syntactic category information. This experiment employs noun/verb homonyms (e.g. “ache”) presented in syntactic context to clarify the mechanisms and representations involved in context-based cohort restriction. Implications for theories positing single versus multiple word-forms in cases of category ambiguity also arise. Using correlations between neural activity in auditory cortex, measured by magnetoencephalography (MEG), and standard and context-dependent cohort entropy and phoneme surprisal variables, we consider the possibility of cohort restriction on the basis of form or on the basis of category usage. Crucially, the form-conditional measure is consistent only with a single word-form view of category ambiguity. Our results show that noun/verb homonyms are derived from single category-neutral word-forms and that the cohort is restricted incrementally in context, by form and then by usage.