The relationship between language and cognitive development and its relevance for infants' mental ability: Longitudinal mediation effects of fine motor development

Abstract

Objectives: Based on both prior theoretical and empirical research, this paper tested the proposition that fine motor development longitudinally mediates the effect of infants' language and cognitive development on later mental ability. Methods: Three data sets from 6 months to 12 months of 114 infants were analyzed with the cross-lagged panel model. The participants' language and cognitive development were assessed through K-ASQ at 6 months and 9 months, and their mental ability (MDI) was assessed by K-BSID-II at 12 months. Results: The cross-lagged panel model using PATH analysis indicated the development of language and cognitive ability was stable over 6 months. Fine motor development at 9 months had a full mediating effect on cognitive development at 6 months on MDI at 12 months. Fine motor development at 9 months had a partially mediated effect on language development at 6 months on MDI at 12 months. When language development was included in the predictor of MDI, cognition was no longer significantly associated with later MDI, suggesting that language plays an important role in the cognition-MDI link. Conclusion: Because fine motor development partially mediated the effect of language development on MDI, early intervention efforts should target both language and fine motor development.