Linguistic significance of babbling: evidence from a tracheostomized infant.

The role of babbling in language development is not well understood. One source of evidence is the utterances of infants who were tracheostomized during the period in which they would normally have produced syllabic vocalization. We describe here the phonetic patterns and linguistic development of a girl called Jenny. She was tracheostomized and generally aphonic from 0.5-1.8 but cognitively and socially normal, with near-normal comprehension of language. Acoustic analyses of Jenny's utterances following decannulation revealed a tenth of the canonical syllables which might be expected in normally developing infants, an extremely small inventory of consonant-like segments, and a marked preference for labial obstruents. In these ways, she resembled a group of infants of the same age who also cannot hear their oral-motor movements, the congenitally deaf, suggesting that the audibility of babbling contributes to its onset. Two months following decannulation, when Jenny was 1.10, she produced only a handful of different words. We think this is because aphonia prevented her from discovering the referential value of vocal expression and discouraged the formation of a phonetic repertoire that could be appropriated for lexical service. This unusual case suggests that babbling normally facilitates the development of language and speech.