The Relationship Between Infant-Directed Prosody and Indices of Lexical Acquisition at 15 Months of Age

The prosodic features of infant-directed speech are described, and several accounts of potential facilitative effects of such distinct prosodic features for the infant’s socioemotional and/or linguistic development are discussed. One of these accounts--that infant-directed prosody facilitates word learning by exaggerating the perceptual salience of novel words in the discourse--is then evaluated through an analysis of two pairs of audio samples taken from the corpora of the Child-Directed Speech Project of the Language Science Research Group based at Washington University at St. Louis. The samples selected were recordings of naturalistic interactions between two mothers and their infants when the infants were nine-and-a-half and 15 months of age. The global prosodic characteristics of the mothers ’ speech in both the nine-and-a-half- and 15-month samples were assessed and compared to the level of productive language demonstrated by the infants at 15 months, an analysis which yielded no significant effects. In addition, based on previous reports that mothers highlight new and/or semantically focused words in speech to infants by placing such words on utterance-final pitch peaks, the pitch peak