The Relationship Between Cognitive and Morphological Skills: Evidence from Turkish Kindergarten Children

This study investigated the role of domain-general cognitive processes, specifically inhibitory control, verbal working memory (WM), and nonverbal reasoning, on children’s productive grammar skills, focusing on Turkish past tense (e.g. fırçala-DI brush-PAST.3sg) and causative suffix (e.g. fırçala-t-TI brush-CAUSE-PAST.3sg), representing the broader categories of inflectional versus derivational morphology, respectively. We tested 84 5-year-old Turkish-learning children from a densely populated district in Istanbul, Türkiye on a sentence completion task to assess the use of morphology. Children were more successful in producing the correct suffix for the past tense than causative suffix, when using both familiar and pseudo verbs. Zero-order correlations showed significant relations between correct suffix use and all cognitive assessments. However, regression analyses revealed that only nonverbal reasoning predicted children’s overall correct suffix use and inhibition predicted it only for the past tense with pseudo verbs. Hence, children who have better reasoning abilities may have more robustly abstracted the grammar rules of their native language. Children with better inhibitory control can more effectively suppress the primed present tense verb and correctly use the past tense. This ability is particularly evident when dealing with pseudo verbs, which make the task more abstract. These findings imply the consideration of domain-general cognition in the development of abstract grammar in childhood.