Sub-visemic discrimination and the effect of visual resemblance on silent lip-reading.

Relevant visual information is available in speakers' faces during face-to-face interactions that improve speech perception. There is an ongoing debate, however, about how phonemes and their visual counterparts, visemes are mapped. An influential hypothesis claims that several phonemes can be mapped into a single visemic category (many-to-one phoneme-viseme mapping). In contrast, recent findings have challenged this view, reporting evidence for sub-visemic syllable discrimination. We aim to investigate whether Spanish words from the same visemic category can be identified or not. We designed a lip-reading task in which participants had to identify target words presented in silent video clips among 3 distractors differing in their visual resemblance from the target. Target words were identified above chance and significantly more than distractors from the same visemic category. Moreover, the error rate for distractors significantly decreased with decreasing visemic resemblance to the target. These results challenge the many-to-one phoneme-viseme mapping hypothesis. [ABSTRACT FROM AUTHOR]