The ERP correlates of thematic role assignment for passive versus active sentences

The current study investigates the ERP correlates of reading passive versus active sentences to provide insight into how comprehenders assign thematic roles and to advance our understanding of the processing mechanisms involved in real-time language processing. This study uses ERPs to investigate how English speakers assign thematic roles while building the structure and meaning of grammatical passive versus active sentences, in which both nouns are equally plausible agents and patients. In two separate experiments, participants exhibited a frontal positivity in response to passive versus active sentences at the point they encountered the past participle form of the lexical verb (e.g., The policeman was tackling the robber/tackled by the robber …). Such frontal positivities have previously been associated with processing grammatical sentences that involve increased syntactic or discourse complexity, rather than structural revision or reanalysis (e.g., Kaan & Swaab, 2003). This suggests that the online revisions necessary for comprehending passive sentences do not involve structural revisions per se, but rather revisions to the expected agent role initially assigned to the sentence-initial noun. These findings expand the scope of ERP research on the assignment of thematic roles and the processing of the morphosyntactic cues that disambiguate such role assignment.