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This study was concerned with the extraction, description, and verification of visual perceptual features underlying vowel lipreading performance. Ten viewers with normal hearing rated the visual similarity of pairs of 15 vowels and diphthongs presented in an /h-g/ context by four speakers. Multidimensional scaling techniques were used to extract potential perceptual features which were then labeled by the experimenters. The resulting perceptual dimensions were correlated with physical measurements of lip shape to evaluate the adequacy of the feature labels. The results indicated that the traditional extended-rounded vowel feature and a vertical lip separation feature were the characteristics most prominent in judging ths stimuli. In addition, a feature related to overall area of maximum lip opening and two features unique to diphthong perception were tentatively identified.
Jackson et al. (Wed,) studied this question.