Phonological processing in deaf children: when lipreading and cues are incongruent

Deaf children exposed to Cued Speech (CS), either before age two (early) or later at school (late), were presented with pseudowords with and without CS. The main goal was to establish the way in which lipreading and CS combine to produce unitary percepts, similar to audiovisual integration in speech perception, when participants are presented with synchronized but different lipreading and auditory information (the McGurk paradigm). In the present experiment, lips and cues were sometimes congruent and sometimes incongruent. It was expected that incongruent cues would force the perceptual system to adopt solutions according to the weight attributed to different sources of phonological information. With congruent cues, performance improved, with improvements greater in the early than the late group. With incongruent cues, performance decreased relative to lipreading only, indicating that cues were not ignored, and it was observed that the effect of incongruent cues increased when the visibility of the target phoneme decreased. The results are compatible with the notion that the perceptual system integrates cues and lipreading according to principles similar to those evoked to explain audiovisual integration.