Bidding on the go: Links between walking, social actions, and caregiver responses in infant siblings of children with autism spectrum disorder.

The development of walking is associated with a shift in how neurotypical infants initiate social interactions. Walking infants are more likely to locate objects in distant places, carry them, and then share those objects by approaching caregivers and using gestures to show or offer their discoveries (i.e., moving bids). The simultaneous organization of the behaviors necessary to generate moving bids requires the coordination of multiple skills-walking, fine motor skills, and gesturing. Infants with an elevated likelihood (EL) for autism spectrum disorder (ASD) exhibit differences and delays in each of these behaviors. This study investigated interconnections between infant walking, social actions, and caregiver responses in 18-month-old EL infants with diverse developmental outcomes (ASD, non-ASD language delay, no diagnosis). We observed 85 infant-caregiver dyads at home during everyday activities for 45 minutes and identified all times when infants walked, instances of walking paired with social action (i.e., approaching the caregiver, approaching while carrying an object, producing a moving bid), and whether caregivers responded to their infants' social actions. There were no group differences in infants' production of social actions. Caregiver responses, however, were more clearly modulated by outcome group. While all caregivers were similarly and highly likely to respond to moving bids, caregivers of EL-ASD infants were substantially more likely to respond when their infants simply approached them (with or without an object in hand). Taken together, this research underscores the complexity of EL infant-caregiver interactions and highlights the role that each partner plays in shaping how they unfold.