Comprehension of Relative Clauses in Chinese Children: Comparing Developmental Dyslexia, Attention-Deficit/Hyperactivity Disorder, and their Comorbidity

This study investigated the comprehension of relative clauses in Chinese children (aged 6 years 10 months to 12 years 11 months) with developmental dyslexia and/or attention-deficit/hyperactivity disorder (ADHD) and explored associations between relative clause comprehension and various linguistic and cognitive factors to enhance our understanding of syntactic processing in these populations. Twenty-two children with dyslexia, 30 with ADHD, 29 with comorbid dyslexia and ADHD, and 31 chronological age-matched typically developing (TD) controls completed a relative clause comprehension task (measuring both accuracy and response latency) and a battery of tasks assessing linguistic and cognitive abilities. All clinical groups showed more accurate performance on subject relative clauses (SRCs) than object relative clauses (ORCs). Children with dyslexia and those with comorbid dyslexia and ADHD did not differ significantly in accuracy or response latency on either SRCs or ORCs. Moreover, they demonstrated significantly lower ORC accuracy than TD controls, with the comorbid group additionally demonstrating longer SRC response latencies than TD controls. Children with ADHD also exhibited much slower response latency than TD controls, particularly for SRCs. Additionally, morphological awareness predicted relative clause comprehension across the clinical groups, whereas better verbal working memory predicted slower processing in ADHD but faster processing in the comorbid group. The observed SRC advantage aligns with the prediction of featural Relativized Minimality, where structural intervention (i.e. syntactic blocking by an intervening element) critically affects children’s relative clause comprehension. The findings confirm the presence of syntactic difficulties in dyslexia and reveal novel evidence of syntactic challenges in ADHD. Morphological awareness and verbal working memory appear to play significant roles in sentence comprehension, highlighting their importance in clinical populations.