BACKGROUND: Early language and motor development may influence cognitive function in a cascading manner later in life. This study aimed to explore the impact of language and motor plasticity during toddlerhood and early preschool years on intelligence in late preschool, with an additional consideration of the influence of ASD and ADHD diagnoses. METHODS: We retrospectively collected medical chart from 423 children aged 2-5 years (316 boys and 107 girls
mean age at Time 1: 3.49 ± 0.98 years), who participated in an early intervention program at a medical center in Northern Taiwan. Language and motor development along with demographic information were assessed during the initial evaluation (Time 1). These assessments were repeated, and intelligence was measured at the follow-up (Time 2). A generalized linear model was used for the data analysis. RESULTS: Receptive language developmental change was the strongest predictor of lower intelligence quotient (IQ) scores, followed by gross, expressive language, and fine motor developmental changes (all p <
0.01). Children with catch-up receptive or expressive language or gross or fine motor development had better IQ outcomes than those with persistent delay (all p <
0.001). There were no ASD-by-developmental type or ADHD-by-developmental type interactions predicting IQ. CONCLUSIONS: Better plasticity in language and motor abilities during toddlerhood and early pre-school years was associated with better intelligence in the late pre-school years. The importance of early and effective interventions for language and motor development has been highlighted.