Babbling development of hearing-impaired and normally hearing subjects.

Phonetic transcriptions of babbling samples from 11 normally hearing subjects, age 4-18 months, were compared with samples from 11 hearing-impaired subjects, age 4-28 months. Longitudinal data were available for all hearing babies and for 8 of the 11 hearing-impaired subjects. The analysis focused on two measures: (a) size of consonantal repertoire over time and (b) proportional occurrence of multisyllabic consonant-vowel utterances. On average, the normally hearing subjects evidenced an increase in size of their consonantal repertoires with age; in contrast, the hearing-impaired subjects in the same age range had smaller repertoires that decreased over time. Comparison of multisyllabic utterances revealed a general tendency for the hearing-impaired subjects to produce fewer multisyllabic utterances containing true consonants and for some of the hearing-impaired children to produce a high proportion of vocalizations with glides or glottal stops. These findings suggest both qualitative and quantitative differences in the babbling of the two groups.