Using ERPs to capture inferential processes guided by prosodic cues

Imagine Mary asks Jack to buy her a rose or a book and he in fact gets her both. In doing so, he indicates that he interpreted or inclusively (i.e., a rose, or a book, or both). However, had he been asked to buy a rose OR a book (with contrastive accent), Jack might have inferred that Mary intended him to buy one gift or the other, but not both; in this case he interpreted the utterance exclusively. In this paper, we test 32 participants and investigate the electrophysiological correlates of contrastive accent and of the ‘not both’ inference which it can generate. Following Relevance Theory, and contra Levinson’s theory of Generalized Conversational Implicatures, we argue that pragmatic inferencing based on such a contextual cue will elicit a distinct electrophysiological component, marking extra processing effort (i.e., the P600). Our results demonstrate the presence of a P3a associated with contrastive accent and a P600-like component as well as a Left Anterior Negativity when contrastive accent leads to pragmatic inferencing. We discuss our results in the context of the linguistic-pragmatic literature and argue that our data are consistent with the idea that the exclusive interpretation requires a deeper analysis than the inclusive interpretation.