Abstract
During language comprehension, online neural processing is strongly influenced by the constraints of the prior context. While the N400 ERP response (300-500ms) is known to be sensitive to a word's semantic predictability, less is known about a set of late positive-going ERP responses (600-1000ms) that can be elicited when an incoming word violates strong predictions about upcoming content (late frontal positivity) or about what is possible given the prior context (late posterior positivity/P600). Across three experiments, we systematically manipulated the length of the prior context and the source of lexical constraint to determine their influence on comprehenders' online neural responses to these two types of prediction violations. In Experiment 1, within minimal contexts, both lexical prediction violations and semantically anomalous words produced a larger N400 than expected continuations (James unlocked the door/laptop/gardener), but no late positive effects were observed. Critically, the late posterior positivity/P600 to semantic anomalies appeared when these same sentences were embedded within longer discourse contexts (Experiment 2a), and the late frontal positivity appeared to lexical prediction violations when the preceding context was rich and globally constraining (Experiment 2b). We interpret these findings within a hierarchical generative framework of language comprehension. This framework highlights the role of comprehension goals and broader linguistic context, and how these factors influence both top-down prediction and the decision to update or reanalyze the prior context when these predictions are violated.
Highlights
In Experiment 1, we contrasted event-related potential (ERP) responses to expected, unexpected, and anomalous critical words, following prior studies that have dissociated the late frontal and posterior positivities
The late posterior positivity/P600 to semantic anomalies appeared when these same sentences were embedded within longer discourse contexts (Experiment 2a), and the late frontal positivity appeared to lexical prediction violations when the preceding context was rich and globally constraining (Experiment 2b)
This finding is consistent with many previous findings relating cloze probability and the N400 (Kutas & Hillyard, 1984), as well as with studies demonstrating facilitated semantic access to words preceded by semantically associated contexts (Camblin, Gordon, & Swaab, 2007; Li et al, 2006)
Summary
In Experiment 1, we contrasted ERP responses to expected, unexpected, and anomalous critical words, following prior studies that have dissociated the late frontal and posterior positivities. Relative to the two other conditions, the amplitude of the N400 would be reduced on critical words that were highly expected given the constraints of the prior verb. Our main question was whether the late frontal and posterior positivities would be produced by words that violated these short, lexically constraining sentence contexts. As noted in the General Introduction, the late frontal positivity is reliably observed to unexpected words in longer sentence and discourse contexts, this effect is not typically observed in single word-priming paradigms. We asked whether these two late positivities would be observed in short, relatively impoverished sentence contexts, which, still constrained for a particular upcoming word
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