This experiment was designed to assess the integration of auditory and visual information for speech perception in older adults. The integration of place and voicing information was assessed across modalities using the McGurk effect. 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 performance?
The performance of three groups of participants was compared: young adults with normal hearing and vision, older adults with normal to near-normal hearing and vision, and young controls, whose hearing thresholds were shifted with noise to match the older adults. Each participant completed a lipreading test and auditory and auditory-plus-visual identification of syllables with conflicting auditory and visual cues.
The results show that on average 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 responses did not differ for the CV tokens across the ages tested. Although there were no significant differences between groups for integration at the syllable level, there were differences in the response alternatives chosen. Young adults with normal peripheral sensitivity often chose an auditory alternative whereas, older adults and control participants leaned toward visual alternatives. In additions, older adults demonstrated poorer lipreading performance than their younger counterparts. This was not related to successful integration of information at the syllable level.
Based on the findings of this study, when auditory and visual integration of speech information fails to occur, producing a nonfused response, participants select an alternative response from the modality with the least ambiguous signal.
As individuals age, there is a decrease in speech recognition abilities. Poorer hearing thresholds contribute substantially to this drop in performance, but it has been suggested that changes in the ability to integrate visual and auditory information may play a limited role as well. This experiment assessed integration of audiovisual information using the McGurk effect, which takes place when conflicting auditory and visual signals are presented and the fused percept contains certain phonetic aspects from each original modality (for example, an auditory /ba/ dubbed onto a visual /ga/ is perceived as /da/, a fused response). On average, the number of fused responses was the same for older and younger adults, but when responses were not fused participants selected an alternative response from the modality with the least ambiguous signal. Young adults with normal peripheral sensitivity often chose an auditory alternative, whereas older adults and young controls (whose hearing thresholds were shifted with noise to match the older adults), leaned towards visual alternatives.
Department of Communication Sciences (K.M.C.), University of Connecticut, Storrs, Connecticut; and University of Minnesota (A.E.C.), Minneapolis, Minnesota.
Address for correspondence: Kathleen M. Cienkowski, Ph.D., Department of Communication Sciences, University of Connecticut, 850 Bolton Road, Box U-85, Storrs, CT, 06269. E-mail: firstname.lastname@example.org.
Received December 12, 2000 accepted December 13, 2001