Saccades and Blinks Index Cognitive Demand during Auditory Noncanonical Sentence Comprehension

Noncanonical sentence structures pose comprehension challenges because they require increased cognitive demand. Prosody may partially alleviate this cognitive load. These findings largely stem from behavioral studies, yet physiological measures may reveal additional insights into how cognition is deployed to parse sentences. Pupillometry has been at the forefront of investigations into physiological measures of cognitive demand during auditory sentence comprehension. This study offers an alternative approach by examining whether eye-tracking measures, including blinks and saccades, index cognitive demand during auditory noncanonical sentence comprehension and whether these metrics are sensitive to reductions in cognitive load associated with typical prosodic cues. We further investigated how eye-tracking patterns differ across correct and incorrect responses, as a function of time, and how each related to behavioral measures of cognition. Canonical and noncanonical sentence comprehension was measured in 30 younger adults using an auditory sentence-picture matching task. We also assessed participants' attention and working memory. Blinking and saccades both differentiate noncanonical sentences from canonical sentences. Saccades further distinguish noncanonical structures from each other. Participants made more saccades on incorrect than correct trials. The number of saccades also related to working memory, regardless of syntax. However, neither eye-tracking metric was sensitive to the changes in cognitive demand that was behaviorally observed in response to typical prosodic cues. Overall, these findings suggest that eye-tracking indices, particularly saccades, reflect cognitive demand during auditory noncanonical sentence comprehension when visual information is present, offering greater insights into the strategies and neural resources participants use to parse auditory sentences.