The impact of prior knowledge on spoken lexical access in children with hearing loss

Northwestern University, Evanston IL

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Abstract

PROJECT SUMMARY Cochlear implants (CIs) promote spoken language development in children with bilateral severe-to-profound sensorineural hearing loss. Yet, many of these children do not obtain age-appropriate language proficiency: children with CIs are typically slower at processing spoken language input and generally have less spoken language experience than chronologically age-matched peers with normal hearing. Delayed language abilities have significant consequences for children's performance in everyday environments, which often require children to process continuous speech rapidly. Rapid speech processing requires instantaneous lexical access, or the ability to retrieve stored representations of words that are contained in spoken input. Instantaneous lexical access may be altered in children with CIs, not only due to their history of auditory and language deprivation, but also due to the inability of CIs to fully restore a high fidelity representation of speech. An inability of children with CIs to process language rapidly may be a source of the variability in language and academic outcomes within this population. To better maximize outcomes in children with CIs, there is a need to understand how lexical access is different in children with CIs. However, a real-time measure that quantifies spoken lexical access moment-by-moment in children with CIs is not established. The objective of the proposed project is to explore how children's hearing ability impacts instantaneous lexical access. Participants will be 92 native English-speaking children who are 6-to-10 years old (n = 36 with bilateral sensorineural hearing loss who use CIs; n = 36 with normal hearing; an additional 20 children with normal hearing will be recruited for stimuli norming). The proposed research will examine two cues helpful in lexical access: phonotactic knowledge (i.e., knowledge of how phonemes are sequenced within a word) and conceptual (i.e., semantic) knowledge. Aim 1 will test children's ability to use phonotactic cues during a classification task based on phonotactic probability. The proposed experiment will test children's ability to discriminate between words that have varying phonotactic probabilities based on the English language (Exp. 1.1). In addition, aim 1 will also test the ability of children to use phonotactic cues to predict word identity in a visual world paradigm (Exp. 1.2). Aim 2 will test children's reliance on conceptual (i.e., semantic) cues on lexical access. Using a modified version of the visual world paradigm from Exp. 1.2, this proposal will test whether semantically related images facilitate lexical access (Exp. 2). All experiments will implement integrated eye-tracking and touch-screen technology, which will allow us to both quantify task accuracy as well as observe the time course of lexical access in children. Findings from this research will establish a foundation of knowledge that will help us further understand how prior hearing and linguistic experience impacts everyday speech comprehension. Future studies will be able to capitalize on this knowledge to assist children with CIs in critical stages of their development.