Babbling and Early Words - Pre-symbolic Productions In Hearing And In Deaf Infants

Cumulative research on pre-speech vocalizations clearly indicates that babbling is in fact structurally and functionally related to early speech. Locke argued in 1996 that when variegated babbling emerges, a consistent relation is identified between vocalizations and specific communicative functions (i.e., protest, question, and statement). At around age eighteen months, the child's phonological system is clearly shaped by the target language's phonetic characteristics, and at that time conventional words emerge.

Indirect evidence for the developmental significance of babbling was published in a revolutionary 1991 paper by Laura Petitto and Paula Marentette on hand babbling in two deaf infants of signing mothers. The argument was that these two infants (who were recorded at ages ten, twelve, and fourteen months) produced far more manual babbling than three matched hearing infants at similar ages. The deaf infants' hand babbling also revealed phonetic features of American Sign Language, suggesting that babbling reflects infants' innate ability to analyze phonetic and syllabic components of linguistic input.