Some profoundly hearing-impaired (HI) speechreaders (lipreaders) achieve levels of accuracy with connected speech that are greater than 80% words correct. These levels of performance are remarkable given that the existing speechreading literature characterizes the visual phonetic stimulus as highly ambiguous and the speechreader's lexicon as mostly filled with homophenous (i.e., visually similar but different sounding) words. The long term goal of this research program is to provide an integrated account of the perceptual, linguistic, and cognitive processes underlying visual speech perception and to characterize the similarities and differences in those processes among individuals with different types of auditory and linguistic experience. To initiate this work we propose four interrelated projects that will study 1) the visual phonetic stimulus, 2) the effects of word homophene, 3) the effects of word knowledge and lexical representation, and 4) the effects of connected speech contexts on word recognition. Direct comparisons will be made among highly proficient speechreader in four populations of subjects, those with: normal hearing, congenital hearing loss, early-onset hearing loss, and adult-onset hearing loss. Methodologies to be employed in the proposed research program will be adapted from the domains of auditory speech perception and spoken word recognition. To the extent that results form speechreading replicate similar ones in the existing literature, it may be concluded that speechreading is but another manifestation of a general human capacity for speech perception, frequently attributed exclusively to audition. Knowledge obtained as a consequence of the proposed research will have applications for the speech and language raining of HI children, speechreading and birotactile aids. Results will provide valuable normative databases for the respective subject populations and have direct application for construction of efficient speechreading tests. Our studies of the perceptual and lexical representations of words by HI subjects will also have implications for reading, and activity whose success in individuals with early hearing loss is highly related to phonological knowledge that may be acquired via speechreading.
