Assessing vocal development in infants and toddlers.

The purpose of this study was to examine changes in prelinguistic vocal production during the first 20 months of life. Vocalizations were classified into 23 mutually exclusive and exhaustive types, and grouped into five ascending levels using the Stark Assessment of Early Vocal Development-Revised (SAEVD-R). Data from 30 typically developing infants, aged 0-20 months, show that older infants attained higher developmental levels on the SAEVD-R than younger infants. Infants 0-2, 3-5, and 6-8 months of age primarily produced vocalizations from Levels 1 (Reflexive), 2 (Control of Phonation), and 3 (Expansion). Infants 9-20 months of age also produced vocalizations from Level 4 (Basic Canonical Syllables). Only infants from 16-20 months of age produced Level 5 (Advanced Forms) vocalizations in significant quantities. The outcomes indicate that the SAEVD-R is a valuable instrument for evaluating prelinguistic vocal development.