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.
