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 moth-ers were observed weekly from 4 to 24 weeks of age in a face-to-face interaction situa-tion. Three patterns of mother–infant communication dynamics were classified: sym-metrical (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 qual-ity of infant nondistress vocalizations are associated with the patterns of mother–in-fant communication and that these associations change developmentally. The results demonstrated that the rates of syllabic and vocalic vocalizations were positively asso-ciated 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 pat-tern (inverted U shape) of the rate of syllabic vocalizations was found in symmetrical communication, a linear increase was found in unilateral communication. A rela-tional approach to infant vocal development in a changing and dynamic communica-tive context is discussed