Infant Communication Across the Transition to Walking: Developmental Cascades Among Infant Siblings of Children with Autism.

New motor skills can shape how infants communicate with their caregivers. For example, learning to walk allows infants to move faster and farther than they previously could, in turn allowing them to approach their caregivers more frequently to gesture or vocalize. Does the link between walking and communication differ for infants later diagnosed with autism spectrum disorder (ASD), whose communicative and motor development differs from their neurotypically developing peers? We prospectively followed two groups of infants longitudinally during the transition from crawling to walking: (1) N = 25 infants with no family history of ASD; and (2) N = 91 infants with an older sibling with ASD. Fifteen infants were later diagnosed with ASD, and 26 infants showed a language delay (but did not receive an ASD diagnosis). After learning to walk, infants without ASD or language delay showed considerable changes in their communication: They gestured more frequently, and increasingly coordinated their gestures and vocalizations with locomotion (e.g., by approaching a caregiver and showing a toy). Infants with language delay showed similar but attenuated growth in their communication. However, infants later diagnosed with ASD did not display enhanced communication after they began to walk.