Sentence comprehension ability and working memory capacity as a function of syntactic structure and canonicity in 5- and 6-year-old children

Objectives: The purposes of this study were to investigate the effects of morphologic and syntactic cues on the sentence comprehension ability of preschool children, and to explore which working memory tasks significantly predict sentence comprehension ability. Methods: Eighteen preschool children (5- and 6-year-old) participated in this study. They performed a sentence comprehension task (SCT) along with five other working memory tasks. The SCT consisted of sentences with three different syntactic structures (active with 2-palce verbs, active with 3-place verbs, and passive) and two types of word order (canonical or non-canonical) which were manipulated within each syntactic structure. Statistical analysis was conducted using a two-way repeated ANOVA, an exploratory factor analysis, and a stepwise regression. Results: There was a significant main effect for sentence type, and the post-hoc comparison displayed lower accuracy in passive than active sentences. Canonicity effect was also significant, with better performance on canonical than non-canonical word order. The two-way interaction was significant as well, showing greater canonicity effects in active than passive sentences. Exploratory factor analysis revealed that working memory tasks could be classified into three different categories: verbal working memory tasks, matrix, and sentence repetition. The strongest predictor for sentence comprehension ability was the verbal working memory task. Conclusion: Syntactic structure and canonicity of word order elicited differential effects on the sentence comprehension ability of 5- and 6-year-old children, and verbal working memory capacity was strongly related to individual differences in understanding sentences with complex structures.