Vocal Development in Infants and Toddlers With Bilateral Cochlear Implants and Infants With Normal Hearing

Purpose The purpose of this study was to investigate the time course of vocal development in infants and toddlers with bilateral cochlear implants (CIs; bilateral CI group) who are acquiring Finnish and to compare their progress to that of infants with normal hearing and typical development (TD group). Method Five thousand nine hundred sixty-four spontaneous utterances of 30 infants and toddlers (15 in both groups) were classified as either precanonical (PC) vocalizations, basic canonical syllables (BCS), or advanced forms (AF) levels. Time course of development and group differences were analyzed in a prospective longitudinal study during a time course of 1 year: before implantation and 1, 3, 6, 9, and 12 months after CI activation for the bilateral CI group and at 6, 9, and 12 months of age for the TD group. Results The least mature PC vocalizations decreased and the BCS and AF vocalizations increased for both the bilateral CI and TD groups during the follow-up period of 1 year. The bilateral CI group produced a lower percentage of PC vocalizations (effect size, η_p ² = .35) and a higher percentage of BCS (effect size, η_p ² = .16) and AF vocalizations (effect size, η_p ² = 0.24) than the TD group. Conclusions The findings of this study showed that vocal development of infants and toddlers with early-identified profound hearing loss is delayed before CI activation. Findings also showed that infants and toddlers with bilateral CIs make rapid advancements in vocal development after implantation compared to infants with typical development. However, their vocal development seems to remain delayed at least during the 1st year of bilateral CI use as compared to the well-documented milestones of infants and toddlers with typical development. Information about the vocal development time course following bilateral CI activation helps parents recognize progress in auditory-guided speech development before the emergence and the use of spoken words in communication.