Influence of gestures on the intelligibility and comprehensibility of utterances with stuttering events in individuals with Down syndrome.

INTRODUCTION

Individuals with Down syndrome (DS) often stutter, which can affect their speech intelligibility. Previous research has shown that manual signs can enhance speech intelligibility and comprehensibility. It remains unclear to what extent spontaneous hand gestures, such as iconic and beat gestures, may enhance intelligibility and/or comprehensibility during utterances with stuttering events.

METHODS

Eleven individuals with DS who stutter provided video-recorded speech samples. From these samples, 60 utterances containing a stuttering event were selected. In half of them, the stuttering events were accompanied by gestures; in the other half, the stuttering events were not accompanied by gestures. The samples were shown to 250 assessors who were blind to the study's goals. Each sample was shown in three visibility conditions: 1) video-with-audio, 2) video-with-audio but with the speaker's mouth covered and 3) audio-only. The assessors rated speech intelligibility on a 7-point Likert scale and transcribed the speech sample. The effect of gesture production, gesture type and the visibility conditions on comprehensibility and intelligibility was examined with a hierarchical multiple linear regression.

RESULTS

When a speaker had used a gesture during a stuttering event, the Likert scale score increased with 0.47 and the accuracy of transcription with 9.07%. There was no difference in effect between the different gesture types. Despite the effect from gesture use, there was no effect of the visibility conditions on the Likert scale or transcription score.

CONCLUSIONS

Gestures positively affect intelligibility and comprehensibility of utterances with stuttering events in individuals with DS by altering the speech production. The possibility of beat gestures as a therapy method should be examined, with caution for the development of maladaptive behaviours.