The Effect of Spontaneous Hand Gestures on Stuttering in Children With Down Syndrome

The parents of the individuals with Down syndrome are given a questionnaire to see if their child can participate in the study. A receptive language test is administered to the individuals with Down syndrome to get an indication of their developmental age. An stuttering discrimination test and a stuttering awareness test were also developed for this study, to see if individuals with Down syndrome are able to hear the difference between stuttered and fluent speech and to see if they are aware of their stuttering. Awareness of stuttering might impact their gesture use.

For the first research question, the relationship between gestures on the stuttering frequency/severity is investigated. To collect this information, video's of spontaneous speech will be analyzed. All the participants are filmed by their parents or caregivers. During the spontaneous speech, the individuals talk about anything they want. Multiple video's with different subjects are filmed per participant since stuttering is very variable. For example, if a child is more excited by one topic than by another, it could increase the stuttering frequency. The same procedure is administered to typically developing individuals. The transcription program CLAN is used to transcribed the videos and to code the stuttering events and the gestures. After this, statistical analysis is used to see if individuals with Down syndrome who stutter differ in their gesture use from the individuals who do not stutter. Next to that, the results of the Down syndrome group will be compared to the typically developing group.

For the second research question, the videos of the individuals are used to investigate the effect of gestures on the intelligibility of stuttering events. There are two conditions: (1) Videos of stuttering events with and without a gesture and (2) audio recordings of stuttering events with and without a gesture (4).The audio recordings are identical to the information in the video recordings.

Typically developing adults who are naïeve to the research question are asked to watch or listen the video/audio recordings of the individuals with Down syndrome. For each recording they are asked to transcribe what they thought the individuals with Down syndrome had said and on a 7-point Likert scale they had to indicate how intelligible they found the speech. The intelligibility results are compared between gesture and no gesture and between audio and video.

The same protocol will be done with video/audio recordings of typically developing individuals who stutter and their results will be compared to those of the participants with Down syndrome.

For the third research question, only the group of children who stutter is retained. There are three experimental conditions and one control condition based on the procedure of Snyder, Waddell & Blachet (2016). In the control condition, the investigator shows three pictograms on a laptop that form a sentence, for example, the cat eats cake. The participants have to produce this sentence. There is a training session to make sure the participant understands to goal of the pictograms and can produce the sentences. The actual test condition contains 7 sentences. In the control condition no gestures or priming is used. The experimental conditions are the same, but priming is induced. In the first experimental condition, the participant gets a hand puppet that must make the same mouth movements as she does, but the puppet needs to start moving before the participant starts talking. In the second experimental condition, the participant does the same thing with the hand puppet, but she has to hold it behind a screen, so she cannot see it herself. In the third condition, it is the investigator who simultaneously mimics the participant with the hand puppet. Each participant does all the conditions, but in a different order, so there is control for a saturation effect. Each experimental condition is preceded by a training session where different forms of prompting are used to teach to participants how to work with the hand puppet.

Additionally, since it is unnatural to walk around with a hand puppet, the same experiment is executed but with the use of beat gestures. These are rhythmical gestures that control the parsing of the speech stream. The children produce the sentences again but this time they make simple up and downward beat gestures during their speech or watch the experimenter make these gestures while they speak. The second experimental condition is eliminated in this case, since beat gestures are often made with two hands.

All the conditions are videotaped and transcribed in CLAN. The stuttering frequency is measured for all the conditions and compared between them. If the beat gestures have a fluency inducing effect, than this might be an indication to develop a new stuttering therapy based on spontaneous hand gestures.