Abstract
Infants' advances in locomotion relate to advances in communicative development. However, little is known about these relations in infants at risk for delays in these domains and whether they may extend to earlier achievements in gross motor development in infancy. We examined whether advances in sitting and prone locomotion are related to communicative development in infants who have an older sibling with autism spectrum disorder (ASD) and are at risk for motor and communication delays (heightened-risk; HR). We conducted a longitudinal study with 37 HR infants who did not receive an ASD diagnosis at 36 months. Infants were observed monthly between the ages of 5 and 14 months. We assessed gross motor development using the Alberta Infant Motor Scales (AIMS) and recorded ages of onset of verbal and nonverbal communicative behaviors. Results indicated increased presence of early gross motor delay from 5 to 10 months. In addition, there were positive relations between sitting and gesture and babble onset and between prone development and gesture onset. Thus, links between gross motor development and communication extend to at-risk development and provide a starting point for future research on potential cascading consequences of motor advances on communication development.