Vocal development in hearing-impaired infants.

Abstract

Vocal development in infants has been analyzed in a variety of ways−acoustically phonetically, and linguistically. An important milestone of vocal development is the onset of canonical babbling, during which the infant produces utterances with the syllabic characteristics of adultlike speech. Infants with profound hearing losses have been observed to develop canonical babbling significantly later than infants with normal hearing [D. K. Oller and R. E. Eilers, Child Develop. 59, 441–449 (1988)]. The purpose of this study was to investigate vocalization behavior in four infants, with hearing losses ranging from moderate to profound degree, from early vocalizations through first words or those vocalizations accompanying first signs. Vocalizations were analyzed with reduced aspect feature transcription (RAFT) [A. E. Carney, J. Acoust. Soc. Am. Suppl. 1 87, S89 (1990)] to describe the range of articulatory behaviors observed. Results were compared to those obtained from a control group of four infants with normal hearing. Onset of canonical babbling and RAFT patterns were analyzed as function of degree of hearing loss, age of identification of hearing loss, and age of amplification and intervention. Results are discussed with regard to the role of auditory feedback in early vocal development. [Work supported by NIH-NIDCD.]