Purpose The purpose of this research was to examine spatial and temporal aspects of articulatory control in children with apraxia of speech (CAS), children with speech delay characterized by an articulation/phonological impairment (SD) and typically developing controls (TD) during speech tasks that increase in word length. Method The participants included 33 children between three and seven years of age (11 CAS, 11 SD, and 11 TD). A motion capture system was used to track jaw, lower lip and upper lip movement during a naming task. Movement duration, velocity, displacement, and variability were measured from accurate word productions. Results Movement variability was significantly higher in the children with CAS as compared to participants in the SD and TD groups. Differences in temporal control were seen between both groups of speech-impaired children and the TD controls during accurate word productions. As word length increased, movement duration and variability differed between the CAS and SD children. Conclusions These findings provide evidence that movement variability distinguishes children with CAS from speakers with SD. Kinematic differences between the CAS and SD participants suggest that these groups respond differently to linguistic challenges.

Purpose This study explored relationships among perceptual, ultrasound, and acoustic measurements of children’s correct and misarticulated /r/ sounds. Longitudinal data documenting changes across these parameters were collected from 2 children who acquired /r/ over a period of intervention and were compared with data from children with typical speech. Method Participants were 3 children with typical speech, recorded once, and 2 children with /r/ misarticulation, recorded over 7–8 months. The following data from /r/ produced in nonwords were collected: perceptually rated accuracy, ultrasound measures of tongue shape, and F3 – F2 distance. Results Regression models revealed significant associations among perceptual, ultrasound, and acoustic measures of /r/ accuracy. The inclusion of quantitative tongue-shape measurements improved the match between the ultrasound and perceptual/acoustic data. Perceptually incorrect /r/ productions were found to feature posteriorly located peaked tongue shapes. Of the children who were seen longitudinally, 1 developed a bunched /r/ and 1 demonstrated retroflexion. The children with typical speech also differed in their tongue shapes. Conclusion Results support the validity of using qualitative and quantitative ultrasound measures to characterize the accuracy of children’s /r/ sounds. Clinically, findings suggest that it is important to encourage pharyngeal constriction while allowing children to find the /r/ tongue shape that best fits their individual vocal tract.

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Oral articulator movement variability is reduced in children across the stabilization of voicing contrast acquisition. Further, the relationship between VOT contrast production and movement variability suggests that a coordinate system between the oral and laryngeal articulators may be refined as children acquire the voicing contrast.

Lip and jaw movements were studied longitudinally in 19-month-old children as they acquired the voicing contrast for /p/ and /b/. A movement tracking system obtained lip and jaw kinematics as participants produced the target utterances /papa/ and /baba/. Laryngeal adjustments were also tracked through acoustically recorded voice onset time (VOT) of the consonants. Across this period of developmental phonological change, the children began to produce VOTs in 2 distinct categories for voiced and voiceless plosives. Specific kinematic differences were observed during oral opening and closing and between spatial and temporal parameters of movement. The development of the voicing contrast was most closely associated with changes in jaw kinematics for oral opening in comparison to that of the lip. Conversely, movements into oral closing were not accompanied by significant increases in jaw, upper lip, or lower lip displacement or velocity, although a decrease in jaw movement variability was found. There was no evidence of phoneme-specific movement differences between /p/ and /b/ in the children or in the adults studied. Spatial coupling between the jaw and upper lip changed significantly across sessions, whereas changes in temporal coupling were not observed. Findings indicate that oral opening and closing have different task requirements and that children modify their articulatory movements to meet the demands of each task. Overall, the findings illustrate how orofacial movements and laryngeal function change in parallel during linguistic development.