Reciprocity in vocal interactions of mothers and infants.

Social responses of 24 mothers and 3-month-old infants were continuously observed and coded in the home to examine reciprocal influences in early vocal interactions. One of 4 dyadic vocal states (simultaneous vocalization, mother vocalizing alone, infant vocalizing alone, mutual silence) was assigned to each consecutive 1-sec interval of the 90-min observational records. The sequence of dyadic vocal states was represented by a first-order transition probability matrix. Transitions between states involving maternal and infant vocal onsets and offsets were analyzed. Results indicated that vocal onsets for both mother and infant were more likely when the other dyad member was vocalizing. There was no evidence of reciprocal influences for vocal offsets. It is suggested that differentiating response onset and offset is necessary for understanding vocal reciprocity in mother-infant interaction.