Nonlinear development of speaking rate in child-directed speech


  • Eon-Suk Ko University at Buffalo



The current study investigated if the speaking rate in Child-Directed Speech (CDS) changes over the course of child language development, and, if so, what the nature of that change is. The developmental path of CDS speaking rate was analyzed in 25 mother-child pairs from longitudinal corpora in CHILDES database. The results were then compared with the developmental pattern of speaking rate in child-produced speech. A parallel analysis was made on the development of mean length of utterance (MLU) in mother and child. The findings suggest that CDS speaking rate dynamically changes with shifts occurring around the onset of child speech production and again during the multiword stage. A parallel pattern of nonlinearity was also observed in the speaking rate of the child and the MLU of both mother and child. Phonological precision effects in CDS (e.g. exaggerated VOT) are explained as a by-product of varying speaking rate. Implications of the findings for studies of language acquisition are discussed.