Tongue and Jaw Movement Characteristics During Speech in Individuals with Down Syndrome

Previous research in speech acoustics has suggested that individuals with Down syndrome may have reduced tongue movement during speech, particularly in the anterior–posterior dimension. However, this has not been confirmed by direct articulatory kinematic examination. The current study examined tongue and jaw movement in adults with Down syndrome (DS) compared to typical adults. The study used the target words “whip” and “bib.” These words were chosen as a previous study showed that “whip” elicits a large tongue movement trajectory in the anterior–posterior dimension compared to “bib.” Eighteen adults with DS and 13 typical adults produced the target words in a carrier phrase “I say a ___ again” while tongue and jaw kinematic data were collected using electromagnetic articulography. Results showed reduced anterior–posterior tongue movement in the Down syndrome (DS) group during “whip” compared to typical adults but not in “bib.” In addition, greater vertical jaw movement in “bib” and reduced articulatory speed were observed in the DS group. The findings confirmed the reduced tongue movement in the anterior–posterior dimension in “whip” but not in “bib.” This suggests that individuals with DS may experience greater articulatory difficulties in words or sentences that elicit greater tongue excursion in the anterior–posterior dimension.