Co-registered eye-movements and brain potentials reveal multiple effects of context across the visual field in natural reading

This study investigates how expectancy and plausibility influence behavioral and neural measures of language processing during naturalistic reading comprehension. Prior event-related potential (ERP) studies show evidence of distinct post-N400 positivities to violations of semantic expectancy and plausibility using artificial serial presentation but have yet to establish these phenomena during naturalistic reading. Therefore, we recorded simultaneous eye-movements and EEG while participants read highly-constraining sentences with expected, unexpected (but plausible), and anomalous target words. Time-locked to the pre-target word, we observed a contextually-graded parafoveal N400 effect. The N400 was facilitated (i.e., reduced) when the word was subsequently fixated, suggesting trans-saccadic integration of semantic features. At target fixation, we also observed a late anteriorly-distributed positivity to unexpected target words and a posteriorly-distributed positivity to anomalous target words, effects that were not present when time-locked to the pre-target word. Eye tracking measures show that readers were sensitive to both expectancy and plausibility at target fixation. In conclusion, we show that readers can begin accessing semantic information in parafoveal vision, but higher-level semantic processing may require the orchestration of both parafoveal and foveal representations.