Infant-directed speech register in children with and without hearing loss

Do children with hearing loss use infant-directed speech while addressing their normal-hearing (NH) infant siblings? This case-study examined speech characteristics in two age-matched children, one with severe-to-profound hearing loss who used bilateral cochlear implants (CIs) for 5 years (the CI child) and one NH child. Both children explained how to assemble a toy and showed a picture book to their NH infant siblings and their mothers. Prosodic characteristics of mean fundamental frequency, fundamental frequency range, utterance duration, and speech rate were collected from each speech sample. The vowel space area was calculated using tokens of cardinal vowels /i/, /a/, and /u/. Both children modified prosodic characteristics in their speech and the CI child expanded his vowel space area addressing his infant sibling compared to their mother. The CI child modified more prosodic characteristics than the NH child. The results demonstrate an effect of the interactional context independent of child hearing status. The findings suggest the beneficial impact of the cochlear implantation on the ability of the CI child to learn the acoustic difference between infant- and adult-directed speech registers and employ the difference in his own speech production.