Auditory syllabic identification enhanced by non-informative visible speech

Recent experiments show that seeing lip movements may improve the detection of speech sounds embedded in noise. We show here that the “speech detection ” benefit may result in a “speech identification ” benefit different from lipreading per se. The experimental trick consists in dubbing the same lip gesture on a number of visually similar but auditorily different configurations, e.g. [y u ty tu ky ku dy du gy gu] in French. The visual stimulus does not enable to identify the syllable, but it provides a temporal cue improving the audio identification of these stimuli embedded in a large level of cocktail-party noise, and particularly the identification of plosive voicing. Replacing the visual speech cue (the lip rounding gesture) by a non-speech one with the same temporal pattern (a red bar on a black background, increasing and decreasing in synchrony with the lips) removes the benefit. 1