Perception of the auditory-visual illusion in speech perception by children with phonological disorders

An example of the auditory-visual illusion in speech perception, first described by McGurk and MacDonald, is the perception of [ta] when listeners hear [pa] in synchrony with the lip movements for [ka]. One account of the illusion is that lip-read and heard speech are combined in an articulatory code since people who mispronounce words respond differently from controls on lip-reading tasks. A same-different judgment task assessing perception of the illusion showed no difference in performance between controls and children with speech difficulties. Another experiment compared children with delayed and disordered speech on perception of the illusion. While neither group perceived many illusions, a significant interaction indicated that children with disordered phonology were strongly biased to the auditory component while the delayed group's response was more evenly split between the auditory and visual components of the illusion. These findings suggest that phonological processing, rather than articulation, supports lip- reading ability.