Auditory-visual speech perception across the lifespan

The perception of speech is a complex task that can involve both auditory and visual information. The set of experiments described below was designed to assess the integration of auditory and visual information for speech perception in older adults. The integral processing of place and voicing information was assessed across modalities using a selective attention task (Garner task) and the McGurk effect. The McGurk effect demonstrates that the visual input can override the auditory input when the two conflict. For example, if a listener hears /bi/ but sees /gi/ the resulting perception is often /di/. The following questions were addressed. (1) Are older adults as successful as younger adults at integrating auditory and visual information for speech perception? (2) Is successful integration of this information related to lipreading ability?; The performance of three subject groups was compared: young adults with normal hearing and vision, older adults with normal to near-normal hearing and vision, and young controls, whose hearing was shifted with noise to match the older adults. Each participant completed a lipreading test, auditory and auditory-plus-visual recognition of syllables, and a Garner task. Two speakers, one male and one female, were used.; The results show that older adults are as successful as young adults at integrating auditory and visual information for speech perception at the syllable level. The number of fused McGurk responses did not differ for the CV tokens across the ages tested. Older adults demonstrated poorer lipreading ability than their younger counterparts although this was not related to successful integration of information at the syllable level. However, when evaluated by the Garner task, the older participants were not consistently successful at integrating information across sensory modalities unlike younger participants. They were found to be differentially affected by the talkers used in the experiments; that is, participants who viewed the male talker showed evidence of integration while those who viewed the female talker did not. Slower processing speed, hearing levels, and failure sensory integration across modalities are factors considered to explain these differences. Finally, the results are discussed within the framework of current theories of speech perception in older adults.