Children with any degree of hearing loss (HL) are at risk for language delays that persist into elementary school. The specific cognitive mechanisms responsible for these deficits remain an open question. A possible contributor to these language deficits is differences in real-time lexical access mechanisms. As a speech signal unfolds, partial word input (e.g., san-) causes the listener to activate multiple lexical candidates (e.g., sandal, sandwich) that are consistent with the signal phonology up to that point. Activation spreads to semantic features of these candidates (e.g., worn on foot, edible), which facilitates activation of semantically related words (e.g., sneaker, apple). Normal hearing adults immediately activate an array of phonological competitors and semantically related items, then rapidly suppress them once there is enough input to disambiguate the target. However, when there is substantial uncertainty in the signal (e.g., for prelingually deaf cochlear implant [CI] users), listeners take a different approach to spoken word recognition: they wait to hear more of the signal before activating any lexical candidates, thus reducing phonological competition. We know that prelingually deaf CI users show delayed activation and reduced phonological competition, but we do not know if listeners with moderately degraded input processed via hearing aids (HAs) show similar patterns of lexical access mechanisms. Furthermore, do these effects manifest in school-age children with HL, who are still undergoing rapid changes in lexical development? Even less is known about how individuals with HL use semantic activation during spoken word recognition. Semantic activation bridges single-word recognition with higher level language comprehension. Research suggests that children with HAs and CIs have weakened lexical-semantic connections, but we do not know if these weaknesses are significant enough to affect real-time semantic activation during running speech.
The aims of this project are to characterize the dynamics of 1) phonological competition and 2) semantic activation during real-time spoken word recognition in school-age children with CIs or HAs, using a visual world paradigm eye- tracking task.
The third aim utilizes previously collected data to examine the longitudinal effects of consistent auditory access on lexical access mechanisms in children with HAs. Findings will provide insight into the extent to which developing language via a degraded auditory signal affects lexical activation and semantic network organization in school-age children. Clinically, findings will indicate whether school-age children with HL are in need of intervention services supporting word recognition efficiency, lexical-semantic connections, or both. The central goal of this project is to improve our understanding of the effects of pediatric HL on the cognitive mechanisms underlying spoken language understanding, which directly addresses the NIDCD priority of increasing our knowledge of the mechanisms of disorders that impair communication. This research will be conducted under the mentorship of leading experts in pediatric HL and real-time spoken word recognition at an institution with an extensive history of innovative research with both children with CIs and children with HAs.
The purpose of this proposal is to characterize the lexical access mechanisms underlying spoken word recognition in school-age children with hearing aids and children with cochlear implants, relative to children with normal hearing. The proposed research is relevant to public health because it will improve our understanding of the effects of pediatric hearing loss on cognitive mechanisms that are foundational to spoken language comprehension. Study findings will improve evidence-based practice by indicating which specific cognitive processes may be at risk in children with hearing loss, and thus should be targeted through clinical intervention.
