Prior research has documented tremendous variability in language outcomes of children with cochlear implants (CIs); despite more than a decade of research, a large portion of this variability remains unexplained. This study characterized the quantity and quality of early linguistic input in naturalistic environments of 14 early-implanted children with CIs to investigate variability across children as a possible source of variation that might help explain language outcome variability. In Chapter 2, daylong audio recordings from home environments of these children were analyzed to examine individual variability in language input they experienced in terms of lexical, morphosyntactic, and social-pragmatic properties. It was found that the quantity and quality of early language input varies substantially across children with CIs, where the degree of variability was comparable in magnitude to what has been reported between the most-advantaged and least-advantaged typically hearing children. In Chapter 3, estimates of the quantity and quality of language input were adjusted to consider environmental noise and reverberation to better represent the "useable" amount of input experienced by the children. It was found that children with CIs are differentially impacted by noise and reverberation in their naturalistic environments, such that some children are doubly disadvantaged in acquiring spoken language, both due to substantial variability in the amount and quality of linguistic input available to them, as well as due to their exposure and susceptibility to environmental noise and reverberation. In Chapter 4, an initial test was conducted to obtain preliminary results regarding how language input factors might shape development of language outcomes in children with CIs. The preliminary results estimating the contribution of language input measures to language outcomes of the children with CIs suggested that measure of speech intelligibility tailored to children with CIs strongly predicted language outcomes. Overall, this study has provided evidence for substantial individual variability across children with cochlear implants in quantity and quality of their early language experience, which were mainly influenced by factors of child-directed speech and environmental noise and reverberation. This evidence-based knowledge can be used by parents and clinicians to effectively adjust early linguistic environments of children with CIs to maximize the advantage of using CIs.
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