The influence of visual speech on lexical access in children

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Project Summary/Abstract: Speech is multimodal in nature: communication partners have access to both auditory and visual speech cues during face-to-face communication. In adults, access to visual speech cues are particularly critical for maintaining accurate speech recognition when the auditory components of speech are compromised by hearing loss, background noise, or sound distortion. In the absence of visual speech cues, poor auditory-only speech recognition has negative cascading effects on the ability to comprehend and learn from the speech input. Despite this evidence, there is an unresolved debate about whether visual speech cues facilitate speech recognition or disrupt the development of auditory skills in children with hearing loss. This debate is reflected in the variety of language intervention approaches that vary in their reliance on visual speech cues. The extent to which visual speech cues are critical to spoken language processing and development in children with hearing loss, however, has not been directly tested. As a first step at addressing this gap in knowledge, the objective of the proposed study is to examine the extent to which the addition of visual speech cues facilitates lexical processing in school-age children with or without hearing loss. Children who are expected to benefit the most from audiovisual speech are children with cochlear implants (CIs), who have permanent bilateral severe-to-profound sensorineural hearing loss. Children with CIs often have poor recognition of auditory-only speech due to limitations of the CIs to fully compensate for the loss of high fidelity auditory representations of speech. The proposed study will test the hypothesis that audiovisual speech facilitates lexical processing relative to auditory-only speech in children with CIs and that this improved processing has positive downstream benefits for language comprehension. Children who are ages 4 to 10 years who use CIs or who have normal hearing (NH) will be recruited. The age range was chosen because audiovisual speech perception matures over the first decade of life. The study will utilize existing validated measures of incremental lexical processing and language comprehension to test the hypothesis. Real-time lexical processing of auditory-only speech (Aim 1) and of audiovisual speech (Aim 2) will be characterized in children with CIs and children with NH. The effects of audiovisual speech on language comprehension skills will also be characterized in the same children (Aim 3). We will relate performance on lexical processing and language comprehension tasks. Theoretically, the results will support the creation of a comprehensive model of lexical processing with and without visual speech cues in school-age children with CIs and children with NH. This work has practical implications for spoken language interventions for children with CIs as well as children with less severe hearing loss, who may differentially utilize visual speech cues. In addition, the results will inform future studies of spoken language interventions that vary in their inclusion of visual speech cues.