Auditory–visual perception of Down syndrome speech (Hennequin et al., 2018)

<div><b>Purpose: </b>This work evaluates whether seeing the speaker’s face could improve the speech intelligibility of adults with Down syndrome (DS). This is not straightforward because DS induces a number of anatomical and motor anomalies affecting the orofacial zone.</div><div><b>Method:</b> A speech-in-noise perception test was used to evaluate the intelligibility of 16 consonants (Cs) produced in a vowel–consonant–vowel context (Vo = /a/) by 4 speakers with DS and 4 control speakers. Forty-eight naïve participants were asked to identify the stimuli in 3 modalities: auditory (A), visual (V), and auditory–visual (AV). The probability of correct responses was analyzed, as well as AV gain, confusions, and transmitted information as a function of modality and phonetic features.</div><div><b>Results:</b> The probability of correct response follows the trend AV > A > V, with smaller values for the DS than the control speakers in A and AV but not in V. This trend depended on the C: the V information particularly improved the transmission of place of articulation and to a lesser extent of manner, whereas voicing remained specifically altered in DS.</div><div><b>Conclusions:</b> The results suggest that the V information is intact in the speech of people with DS and improves the perception of some phonetic features in Cs in a similar way as for control speakers. This result has implications for further studies, rehabilitation protocols, and specific training of caregivers.</div><div><br></div><div><b>Supplemental Material S1.</b> General information about intelligibility and orofacial specificities of the four speakers with Down syndrome (DS).</div><div><br></div><div><b>Supplemental Material S2.</b> Details of transmitted information computation.</div><div><br></div><div><b>Supplemental Material S3.</b> Effect of presentation order on <i>Prob_correct_VCV</i>.</div><div><b><br></b></div><div><b>Supplemental Material S4. </b>Analysis of the probability of correct consonant identification as a function of experimental condition.</div><div><br></div><div>Hennequin, A., Rochet-Capellan, A., Gerber, S., & Dohen, M. (2018). Does the visual channel improve the perception of consonants produced by speakers of French with Down syndrome? <i>Journal of Speech, Language, and Hearing Research, 61, </i>957–972.</div>