Rapid Increases in Children's Spontaneous and Responsive Speech Vocalizations Following Cochlear Implantation: Implications for Spoken Language Development.

Objectives: Cochlear implants are the most effective means to provide access to spoken language models for children with severe to profound deafness. In typical development, spoken language emerges gradually as children vocally explore and interact with caregivers. But it is unclear how early vocal activity unfolds after children gain access to auditory signals, and thus spoken language, via cochlear implants, and how this early vocal exploration predicts children's spoken language development. This longitudinal study investigated how two formative aspects of early language-child speech productivity and caregiver-child vocal interactions-develop following cochlear implantation, and how these aspects impact children's spoken language outcomes.

Design: Data were collected via small wearable recorders that measured caregiver-child communication in the home pre- and for up to 3 years post-implantation (N = 25 children, average = 167 hours/child, 4,180 total hours of observation over an average of 11 unique days/child). Spoken language outcomes were measured using the Preschool Language Scales-5. Growth trajectories were compared with a normative sample of children with typical hearing (N = 329).

Results: Even before implantation, all children vocalized and vocally interacted with caregivers. Following implantation, child speech productivity (β = 9.67, p < 0.001) and caregiver-child vocal interactions (β = 12.65, p < 0.001) increased significantly faster for children with implants than younger, hearing age-matched typical hearing controls, with the fastest growth occurring in the time following implant activation. There were significant, positive effects of caregiver-child interaction on children's receptive, but not expressive, spoken language outcomes.

Conclusions: Overall, children who receive cochlear implants experience robust growth in speech production and vocal interaction-crucial components underlying spoken language-and they follow a similar, albeit faster, developmental timeline as children with typical hearing. Regular vocal interaction with caregivers in the first 1 to 2 years post-implantation reliably predicts children's comprehension of spoken language above and beyond known predictors such as age at implantation.