Vocal Development of Typically Developing Infants

Abstract

This study investigated changes in the prelinguistic vocal production of typically developing infants aged 5-20 months based on Stark Assessment of Early Vocal Development-Revised (SAEVD-R). Fifty-eight typically developing infants participated in the study, and they were divided into four age groups, 5-8 months, 9-12 months, 13-16 months, and 17-20 months of age. Vocalization samples were collected from infants' play activities and were classified into 5 levels and 23 types using SAEVD-R. The results revealed that the four age groups showed significant differences in production proportion of vocalization levels. Level 1, 2, 4, and 5 vocalizations exhibited significantly different across the four age groups. Level 3 was predominantly produced across every age group. Therefore, the vocalization level was not significantly different across the four age groups. Especially, vowels in Level 3 vocalization predominantly produced across all ages during a long period. Also, significant increases in the proportion of Levels 4 and 5 occurred after 9 months, which suggested that the production of cannonical syllables is a key indicator of advancement in prelinguistic vocal development. The results have clinical implication in early identification and speech-language intervention for young children with speech delays or at risk.