Sentence comprehension in a wider discourse: ERP studies on syntax, sense, and reference

It has been known for a long time that event-related brain potentials can provide valuable information about the nature and time course of sentence comprehension. However, in part because using brain measures is difficult enough as it is, most psycholinguists have until recently limited their use of ERPs to the comprehension of single sentences presented in isolation. Over the past five years, we have begun to use ERPs to study the comprehension of sentences in the context of a wider discourse (usually a 2- or 3-sentence mini-story). In my lecture, I will review some of the results of this project. One of the things our work has shown is that when people read or listen to a sentence embedded in a wider discourse, they immediately relate the meaning of every incoming word to their knowledge of this wider discourse. We know this because words that are coherent in their local carrier sentence but anomalous with respect to the wider discourse (e.g., 'David ate a sandwich with salami and mustard' in a discourse that just described David as a strict vegetarian) elicit an N400 effect, emerging at about 150-250 ms from word onset during reading as well as listening. With spoken language, listeners actually detect that something is wrong well before the anomalous word has been fully heard. Moreover, because the discourse-dependent N400 effect is indistinguishable from the classic sentence-dependent N400 effect, we can infer that the generator of the N400 doesn't care whether the interpretive context for a word is supplied by a discourse or by just the first few words of a single unfolding sentence. Next to this evidence for rapid discourse-dependent semantic processing, I will briefly review the ERP evidence for discourse-dependent referential and syntactic processing in spoken and written language comprehension. Taken together, our findings suggest that in comprehending an unfolding sentence, the syntactic, semantic, and referential implications of each incoming word are immediately related to a mental model of what the wider discourse is about. The results also suggest that because of their potential selective sensitivity, ERPs can play a crucial role in keeping track of the many different types of linguistic analysis that simultaneously occur when comprehending a piece of discourse