Effects of Word Order Canonicity and Semantic Plausibility on Sentence Comprehension in Mild Cognitive Impairment: An Eye Tracking Study

Objectives: The purpose of this study was to investigate the differences in performance of sentence comprehension performance based on word order canonicity and semantic plausibility in healthy adults (HA) and persons with mild cognitive impairment (MCI), and to examine the underlying processing mechanisms using eye-tracking. Methods: Twenty three HA and twenty three individuals with MCI participated in a sentence comprehension task manipulated for word order canonicity (canonical vs. noncanonical) and semantic plausibility (high vs. low). Target Advantage scores were analyzed to examine gaze preference patterns across sentence phrases. Results: Individuals with MCI showed reduced accuracy and longer response times compared to healthy older adults. Both groups exhibited lower accuracy and longer response times in sentences with noncanonical word order and low semantic plausibility. According to the eye-tracking data, in the second noun phrase, HA preferred the filler image, whereas individuals with MCI preferred the target image. In the verb phrase, HA demonstrated a stronger preference for the target image compared to the individuals with MCI. Conclusion: This study examined sentence comprehension performance and eye-tracking patterns in HA and individuals with MCI, with a focus on syntactic factors (word order canonicity) and semantic factors (semantic plausibility). The results suggest that semantic plausibility may serve as an important variable in differentiating between the two groups.