A comparison between cerebral-palsied and normal adults in the perception of auditory-visual illusions

Abstract

Listeners obtain information about speech both from listening to a talker and by using visual cues from the talker’s face. As demonstrated in the McGurk effect, conflicting auditory and visual cues produce illusions. The present experiment investigated whether lack of experience with normal speech production affects the perception of auditory-visual illusions. Adults with cerebral palsy (CP) who have been severely dysarthric since birth were compared to normally speaking adults on two types of illusions: (1) auditory /aba/ paired with visual /aga/ which typically produces a /da/ illusion; and (2) auditory /aga/ paired with visual /aba/ which typically produces a /bga/ illusion. The number of illusory responses was compared for each group. There was no difference between groups in the number of /da/ illusions. However, adults with CP perceived fewer /bga/ illusions than normal adults. These results suggest that lack of experience articulating speech inhibits a listener’s ability to perceive unusual English phoneme clusters like /bga/. [Research supported by NICHD.]