Abstract
The aim of the current paper was to use data from a prospective study to assess the impact of early motor skills on the rate of language development in infants with an older sibling with autism spectrum disorder (ASD), who are at increased risk of developing ASD themselves. Infants were tested prospectively at four points (7, 14, 24 and 36 months), and were assessed for ASD at the last visit. Latent growth curve analysis was used to model rate of language development using the Vineland Adaptive Behavior Scales between 7–36 months in infants at high and low familial risk for ASD. Motor scores from the Mullen Scales of Early Learning at 7 months were used as predictors of language growth. Gross Motor scores predicted the subsequent rate of expressive, but not receptive, language development in at-risk siblings who were later diagnosed with ASD. Although the pattern was similar for fine motor skills, the relationship did not reach significance. It seems that early motor delay impacts the rate of development of expressive language, and this may be of particular importance to infants at increased risk of developing ASD.