Investigating speechreading and deafness.

BACKGROUND The visual speech signal can provide sufficient information to support successful communication. However, individual differences in the ability to appreciate that information are large, and relatively little is known about their sources. PURPOSE Here a body of research is reviewed regarding the development of a theoretical framework in which to study speechreading and individual differences in that ability. Based on the hypothesis that visual speech is processed via the same perceptual-cognitive machinery as auditory speech, a theoretical framework was developed by adapting a theoretical framework originally developed for auditory spoken word recognition. CONCLUSION The evidence to date is consistent with the conclusion that visual spoken word recognition is achieved via a process similar to auditory word recognition provided differences in perceptual similarity are taken into account. Words perceptually similar to many other words and that occur infrequently in the input stream are at a distinct disadvantage within this process. The results to date are also consistent with the conclusion that deaf individuals, regardless of speechreading ability, recognize spoken words via a process similar to individuals with hearing.