Influences of infants' and mothers' contingent vocal responsiveness on young infants' vocal social bids in the Still Face Task.

Infants' social bids in the still face phase of the Still Face Task demonstrate their emerging sense of self agency as these behaviors happen in the absence of the partner's social overtures. The study examined the role of infants' contingent responsiveness to their mothers in social interactions on their social bidding to the mother when she becomes unresponsive. Social bids are non-distress vocalizations or smiles while looking at the unresponsive partner. Infants and their mothers longitudinally engaged in the Still Face Task when infants were one, two, and three months. At two months, infant non-distress vocalizations and smiles and contingent vocal and smiling responsiveness increased in the initial interactive phase and vocal and smile social bids increased in the still face phase. Infant contingent vocal responsiveness predicted infant vocal social bids but infant contingent smiling responsiveness did not predict infant smile social bids. Infant contingent vocal responsiveness was a stronger predictor than infant non-distress vocalizations per se of infant vocal social bids at two and three months. However, maternal contingent vocal responsiveness was the primary predictor of infant vocal social bids at these ages. Maternal contingent responsiveness to infant behavior allows infants to sense their agency in affecting their mothers' behavior. Yet infants are active participants, becoming contingently responsive to their mothers, which facilitates their awareness that they are effective agents in instigating social interaction, as demonstrated by social bids.