Embedding (im)plausible clauses in propositional attitude contexts: Modulatory effects on the N400 and late components

Abstract

How do comprehenders track dependencies between the plausibility of embedded clauses and of the sentences in which they occur? We investigated processing of Norwegian propositional attitude sentences with plausible or implausible complement clauses (‘Magnus {knows/believes/dreams/doubts/imagines} that mosquitos live off {blood/vodka}’). Using ERPs, we tested the hypothesis that the amplitude of the N400 component is sensitive to the plausibility of the attitude sentence as a whole, as opposed to that of the complement clause. If the hypothesis is correct, the N400 should be larger for implausible clauses (vodka > blood) under know and believe, it should be canceled (vodka ~ blood) under dream, and it should be reversed (vodka < blood) under doubt and imagine. These predictions were not borne out. We found N400 effects for all attitude sentences, tracking the plausibility of complement clauses (vodka > blood), except for imagine (‘innbille’ in Norwegian has a counterfactual sense), where the effect was suppressed, but not reversed. Moreover, we observed modulations of late ERP components for implausible clauses (vodka > blood) under doubt and imagine, i.e., when the plausibility of the attitude sentence requires an implausible complement clause. We propose that (a) the N400, in general, reflects processing of semantic relations in phrasal and clausal contexts, and it is not necessarily sensitive to sentence plausibility, and (b) later components index integration of information from embedded clauses into a sentence model.