Infant Vocal Development in a Dynamic Mother-Infant Communication System

This study is an investigation of the development of infant vocalization in a changing and dynamic mother-infant communication system. Thirteen infants and their mothers were observed weekly from 4 to 24 weeks of age in a face-to-face interaction situation. Three patterns of mother-infant communication dynamics were classified: symmetrical (mutual engagement by mother and infant), asymmetrical (mother active while infant inactive), and unilateral (mother active while infant disengaged). Two types of infant nondistress vocalizations were categorized: syllabic (speechlike) and vocalic (nonspeechlike) vocalizations. It was hypothesized that the quantity and quality of infant nondistress vocalizations are associated with the patterns of mother-infant communication and that these associations change developmentally. The results demonstrated that the rates of syllabic and vocalic vocalizations were positively associated with symmetrical communication but negatively associated with unilateral communication. Syllabic vocalizations were more likely to occur in symmetrical mother-infant communication. Developmentally, whereas a curvilinear growth pattern (inverted U shape) of the rate of syllabic vocalizations was found in symmetrical communication, a linear increase was found in unilateral communication. A relational approach to infant vocal development in a changing and dynamic communicative context is discussed.