Language and motor abilities of preschool children who stutter: evidence from behavioral and kinematic indices of nonword repetition performance

Abstract

Stuttering is a disorder of speech production that typically arises in the preschool years, and many accounts of its onset and development implicate language and motor processes as critical underlying factors. There have, however, been very few studies of speech motor control processes in preschool children who stutter. Hearing novel nonwords and reproducing them engages multiple neural networks, including those involved in phonological analysis and storage and speech motor programming and execution. We used this task to explore speech motor and language abilities of 31 children aged 4-5 years who were diagnosed as stuttering. We also used sensitive and specific standardized tests of speech and language abilities to determine which of the children who stutter had concomitant language and/or phonological disorders. Approximately half of our sample of stuttering children had language and/or phonological disorders. As previous investigations would suggest, the stuttering children with concomitant language or speech sound disorders produced significantly more errors on the nonword repetition task compared to typically developing children. In contrast, the children who were diagnosed as stuttering, but who had normal speech sound and language abilities, performed the nonword repetition task with equal accuracy compared to their normally fluent peers. Analyses of interarticulator motions during accurate and fluent productions of the nonwords revealed that the children who stutter (without concomitant disorders) showed higher variability in oral motor coordination indices. These results provide new evidence that preschool children diagnosed as stuttering lag their typically developing peers in maturation of speech motor control processes.

Educational objectives: The reader will be able to: (a) discuss why performance on nonword repetition tasks has been investigated in children who stutter; (b) discuss why children who stutter in the current study had a higher incidence of concomitant language deficits compared to several other studies; (c) describe how performance differed on a nonword repetition test between children who stutter who do and do not have concomitant speech or language deficits; (d) make a general statement about speech motor control for nonword production in children who stutter compared to controls.

Fig. 1

Sample kinematic data for “mabteebeebee” from a typically developing child, left column, and a child who stutters, right column. The top panel for each child shows the lip aperture trajectories for the sets of 5 early productions (thinner, red traces) and 5 later productions (thicker, blue traces). The top graphs show distance between the upper lip and lower lip (lip aperture signal) in mm as a function of real time. The lower plots show the same trajectories after time and amplitude normalization. From the two top plots, it is apparent that the two children are producing very different movement patterns. The CWNS child produced larger oral openings for the first syllable, whereas the CWS produced opening movements of about the same size for all four syllables. Also from the original data plots, we see that the red (early 5) trajectories tend to be of longer duration compared to the thicker, blue trajectories for both children, indicating the overall practice effect we observed: the later productions were produced faster. Also the blue trajectories tend to converge together in a tighter pattern compared to the early set. This suggests that the later productions were more consistently coordinated, and this should be reflected in lower lip aperture variability indices for the later compared to the early trials. This was the case. For the CWNS child the early trials LA Var was 18.7 and for the later trials 8.5; while for the stuttering child the indices were early 31.2 and later trials 21.4. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)

Fig. 2

Percent phonemes correct (mean and SEM) in the Dollaghan and Campbell nonword repetition task (1998). CWNS, typically developing children; CWS, children who stutter who passed all language and speech screening test; CWS+SS, children who stutter with a phonological disorder; and CWS+LI, children who stutter with concomitant language disorder.

Fig. 3

Lip aperture variability indices (mean and SEM) for the CWNS (typically developing children) and CWS (children who stutter) groups for m1, “mab,” m2, “mabshibe,” and m5, “mabteebeebee” for the early (E) and later sets of trials (L).

Fig. 4

Overall duration (mean and SEM) for the CWNS (typically developing children) and CWS (children who stutter) groups for m1, “mab,” m2, “mabshibe,” and m5, “mabteebeebee” for the early (E) and later sets of trials (L).