Discourse coherence modulates use of predictive processing during sentence comprehension

Authors: Georgia Carter and Paul Hoffman

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Context has been shown to be vitally important for comprehension. Lexical processing is facilitated when words are highly predictable given their local sentence context, suggesting that people pre-activate likely upcoming words to aid comprehension. However, this facilitation is affected by knowledge about the global context in which comprehension takes place: people predict less when in an environment where expectations are frequently violated. The current study investigated whether discourse coherence is an additional cue that comprehenders use to modulate lexical prediction. In a series of online, self-paced reading experiments, participants read target sentences preceded by short contextual preambles. Local facilitation effects were manipulated through the cloze probability of a critical word within the target sentence and discourse coherence was manipulated by varying the degree to which the target sentence was consistent with the information presented in the preamble. In the first two experiments, target sentences were read more slowly when they occurred in less coherent discourses, but no local facilitation effects were observed. In the third experiment, we strengthened the predictability manipulation by using semantically anomalous critical words. In this experiment, predictable words were processed more quickly and anomalous words more slowly when they occurred in highly coherent discourse. Our results suggest that comprehenders are sensitive to shifts in the topic of discourse and that they downregulate predictive processing when they encounter incoherence in the discourse. This is consistent with recent theoretical accounts suggesting that comprehenders flexibly engage in predictive processing, pre-activating semantic and lexical information less when their expectations are less likely to be reliable.