Semantics and syntax in sentence comprehension: An analysis of their relationship in time using event-related potentials
A central issue in psycholinguistics is how we process semantic and grammatical information and how these processes interact during online comprehension. Previous studies have yielded inconclusive results on how and when this interaction occurs; it is unclear whether these processes are continuously interacting or if they only interact at a later stage. The purpose of this study was to examine this interaction using the N400 and P600 as indices of semantic and grammatical processing, respectively. Native speakers of Spanish were presented with Spanish sentences containing a target adjective that was either semantically and grammatically correct or disagreed in meaning, grammatical gender, or both with the preceding noun. The adjectives were embedded in a range of weakly to strongly constraining sentences in order to compare the interaction effect as a function of contextual constraint. Semantic violations elicited a robust N400 effect followed by a late positivity, while grammatical gender violations elicited a left-lateralized negativity followed by a P600 effect. The interaction of semantics and gender was observed only at the P600 time window. Interestingly, sentential constraint modulated the onset latency of the N400 to semantic violations, while the P600 due to gender violations was modulated by constraint in a graded fashion. The findings seem to support late interaction models whereby semantic and grammatical processes are initially independent and interact only at a later phase. However, the interaction may be modulated by the amount of contextual information available, as both processors are combining efforts to predict upcoming words.