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RESEARCH PRODUCT

Audiovisual speech perception in children with developmental language disorder in degraded listening conditions.

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Purpose The effect of the signal-to-noise ratio (SNR) on the perception of audiovisual speech in children with and without developmental language disorder (DLD) was investigated by varying the noise level and the sound intensity of acoustic speech. The main hypotheses were that the McGurk effect (in which incongruent visual speech alters the auditory speech percept) would be weaker for children with DLD than for controls and that it would get stronger with decreasing SNR in both groups. Method The participants were 8-year-old children with DLD and a sample of children with normal language development. In the McGurk stimuli, the consonant uttered by the voice differed from that articulated by the face. Three sound intensities (24, 36, and 48 dB) and noise levels (−12, 0, and +6 dB) were used. Perception of unisensory visual speech was also measured. Results The children with DLD experienced a weak McGurk effect, that is, a weak influence of visual speech on audiovisual speech perception, which remained rather constant across SNR levels. The children with DLD were inaccurate at lipreading. Conclusions Children with DLD have problems in perceiving spoken consonants presented audiovisually and visually. The weaker McGurk effect could be accounted for by the poorer lipreading ability of children with DLD.