Early Ontogeny of Vocal Behavior of Japanese Infants in Response to Maternal Speech


  • I am indebted to Shozo Kojima, Toshikazu Hasegawa, and Tomoko Taniguchi for their assistance with data collection and reduction. I am grateful to the two anonymous reviewers for their invaluable comments.

Requests for reprints should be sent to Nobuo Masataka, Department of Anthropology, Faculty of Science, The University of Tokyo, Hongo, Bunkyo, Tokyo 113, Japan.


Discriminant analysis was used to distinguish statistically between the comfort-state vocalizations uttered by Japanese infants following 5 different types of pitch contours of maternal speech. Ontogenetic changes of their vocal behaviors were investigated during the first 5 months of life. Structural variability in infant vocalizations across variants of maternal speech was found to be characterized by a set of quantifiable physical parameters. However, infant's age when a vocalization was recorded was not an important contributor. Successful attempts at cross-validation, in which the discriminant profiles derived from one sample of vocalizations were used to classify a second set of vocalizations, indicated that the result obtained was not an artifact of using the same data set to derive the profiles to test reclassification accuracy. Proportion of cross-validated vocalizations that were misclassified decreased as age increased. The results of the present study demonstrate that a statistically significant relation exists between acoustic features of maternal speech and those of following infant vocalizations, and that such a relation strengthens over age.