An Observational Analysis on the Function of Infant Vocalization : A Case of a Down Syndrome Infant

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This study reveals the functional development of the Down syndrome's vocalization in his early infancy. Subjects were two mother-infant pairs : one infant was with Down syndrome and the other infant was non-retarded. They were videotaped for six hours when the infants were 5-and 7 month old and when the Down syndrome infant was 9 month-old. In the observation, the three kinds of mothers' behavior were picked up, holding her baby in her arms (holding), feeding milk or weaning food to her baby (feeding), and speaking to her baby (speech). Sixty-second infants' vocalization before and after their mother's feeding and holding were analyzed. Infants' vocalization was classified into three categories, cry, non-cry and faking cry. Three kinds of vocalization patterns were recorded in the unit of second. The acoustic features of fundamental frequency and duration in Down syndrome infant's vocalization were analyzed. Three results were obtained. 1) There were no non-cries of 15 seconds before holding except in the data of the 5 month-old Down syndrome infant. 2) Developmentally Down syndrome infant's non-cries before holding existed longer than the "normal" one. 3) Down syndrome infant's vocalization could not be classified into clear categories compared to the non-retarded infant. From these results, we conclude that the Down syndrome infant has some backwardness in the development of functional use of vocalization.
横浜国立大学の論文