Everyday face-to-face conversations often occur in the presence of adverse environmental conditions such as background noise and/or poor lighting. In this second stage of our research on audiovisual speech perception and aging, we turn our attention to comprehension of discourse (i.e., extended verbal expression) under both favorable and unfavorable conditions. First, we propose to determine whether auditory-visual integration is a processing module that operates subsequent to the encoding of the auditory and visual speech signals, as current theoretical models assume and whether age differences emerge as the levels of auditory and visual speech information are decreased. To this end, we have developed a novel integration enhancement index that statistically controls for differences in unimodal speech perception. Using this index, we will assess integration enhancement in younger and older adults under both favorable and unfavorable listening and viewing conditions. Second, we plan to assess the extent to which age and degraded environmental conditions impair audiovisual discourse comprehension. Third, we will determine the sensory and cognitive factors that predict individual differences in older adults'discourse comprehension using measures of hearing and visual acuity, auditory and visual speech perception, processing speed, integration enhancement, and working memory. Fourth, we will examine longitudinal changes in audiovisual discourse comprehension in a group of older first-time hearing aid users over a period of 18 months. Our goal in this final study is to examine how performance changes, and whether the influence of sensory and cognitive variables on audiovisual discourse comprehension varies over time. Overall, this project represents a unique opportunity that brings together clinical audiological researchers and cognitive psychologists for the purpose of developing aural rehabilitation procedures for older persons that are grounded in well-developed theoretical models of audiovisual discourse comprehension.
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