Prosodic characteristics of speech directed to adults and to infants with and without hearing impairment

Infant-direct (ID) and adult-directed (AD) speech are distinguished via multiple acoustic-prosodic characteristics, but it is unclear how these differences map onto linguistic constructs, including pitch accents, prominences, and phrasal boundaries, or how a child’s hearing impairment affects caregiver prosody. In two studies, trained analysts coded prosody in corpora of mothers reading to their children (ID condition) or another adult (AD condition). In Study 1, 48 mothers read a storybook to their infants aged 3, 9, 13, or 20 months or an experimenter. In Study 2, 11 mothers read a storybook to their child with a cochlear implant at 3 months post-implantation or to an experimenter; each hearing-impaired child was paired two normal-hearing dyads based on the hearing-impaired child’s chronological age and amount of hearing experience. ID speech contained a greater density of pitch accents and prominences than AD speech. There was no difference in distributions of phrase boundaries across speech styles, and hearing status did not mediate effects of speech style on prosody. Results suggest that acoustic differences distinguishing ID and AD speech map onto combined phonological structural and gradient paralinguistic characteristics and contribute to understanding effects of child hearing loss on caregiver input. [Work supported by NIH Grant 5R01DC008581-07.]