Viseme identification ability and its effect on auditory consonant perception in Mandarin-speaking younger and older adults

• Older adults exhibited inferior viseme recognition compared to younger adults. • Highly visible visemes facilitated audiovisual speech perception for older adults. • Visual and auditory abilities predicted audiovisual enhancements in older adults. This study examined age-related differences in the perceptual organization and identification of Mandarin visemes, as well as the contribution of visual information to auditory consonant perception in younger and older adults.. Analyses included hierarchical clustering of visual confusability patterns, viseme identification accuracy, visual enhancement for each viseme category and age group, and confusion matrices of articulation features. The results showed that older adults exhibited reduced differentiation among viseme categories, while the overall confusability structure was largely preserved.. Older adults exhibited lower identification accuracy for all visemes except for Palatals, whereas audiovisual enhancement was comparable across age groups for most categories, except for retroflexes. Across both groups, Viseme Bilabials and Labiodental were identified more accurately and showed greater audiovisual enhancement than other categories. Moreover, audiovisual input reduced not only confusions across places of articulation but also across manners of articulation. These findings suggest that visual speech cues remain effective in supporting consonant perception in older adults.