Features of infant vocalization at successive age levels

Abstract

It has been suggested that speech motor abilities in infants emerge within an invariant sequence of levels. The present study was designed to describe the articulatory‐acoustic features of infant vocalization and thus, to identify those that may be characteristic of infant utterances at different age levels or developmental levels. The vocalizations of five infants were studied on a limited longitudinal basis. The age ranges of these infants were 2–10, 12–23, 26–36, 40–55, and 72–88 weeks, respectively. Forty to 50 vocalizations were selected randomly from each infant's output at the first and at the last recording session for a total of ten recordings. These vocalizations were analyzed acoustically by means of computer‐assisted spectral analyses. Measurements of duration and frequency were made from the resulting displays, which also provided information to listeners as they judged voicing and vocalic and consonantal features. Analyses of these preliminary data suggest that three classes of features may provide useful indices of development of infant speech motor abilities: namely, (1) pitch contour; (2) vocalic features; and (3) consonantal features. The relative importance of each will be discussed. [Work supported by Bureau of Community Health Services, Maternal and Child Health.]