Auditory sensitivity and the prelinguistic vocalizations of early-amplified infants.

Purpose: Vocalization development has not been studied thoroughly in infants with early-identified hearing loss who receive hearing aids in the 1st year of life. This study sought to evaluate the relationship between auditory sensitivity and prelinguistic vocalization patterns in infants during the babbling stage.

Method: Spontaneous vocalizations of 15 early-identified infants with varying degrees of hearing sensitivity, from normal to profound hearing loss, were audiotaped and perceptually transcribed. Associations between the infant's unaided pure-tone average and the following vocalizations were explored: canonical babbling ratio, percentage of utterances containing canonical syllables, canonical syllable shapes, number of syllable sequences, and consonant-onset patterns in canonical syllables.

Results: Hearing sensitivity was significantly associated with the percentage of utterances containing canonical syllables, the vocalization types used in utterances, and canonical syllable shapes used by the infants.

Conclusions: Auditory sensitivity contributes significantly to the emergence of babbling patterns. In addition, there is a need for continued study of the vocalizations of infants with milder forms of hearing loss, because in this study, their vocalizations were highly variable despite having received early amplification.