Influences of Sentence Length and Syntactic Complexity on the Speech Motor Control of Children Who Stutter

Abstract

Purpose To investigate the potential effects of increased sentence length and syntactic complexity on the speech motor control of children who stutter (CWS). Method Participants repeated sentences of varied length and syntactic complexity. Kinematic measures of articulatory coordination variability and movement duration during perceptually fluent speech were analyzed for 16 CWS and 16 typically developing children (CTD) between 4 and 6 years of age. Behavioral data from a larger pool of children were also examined. Results For both groups, articulatory coordination variability increased with sentence length. For syntactically simple sentences, CWS had higher coordination variability than CTD. There was no group difference in coordination variability for complex sentences. Coordination variability increased significantly with complexity for CTD, while that of CWS remained at the high levels seen for simple sentences. There was a trend for higher overall coordination variability in CWS, compared to CTD. For both groups, movement duration was greater for syntactically complex, as compared to simple, sentences. Conclusions Results indicate more variable speech motor coordination during fluent speech production in many CWS, as compared to CTD. Disproportionate effects of sentence length and syntactic complexity on articulatory coordination variability and movement duration were not found for CWS. Considerable individual differences in performance were observed.

A Lag in Speech Motor Coordination During Sentence Production Is Associated With Stuttering Persistence in Young Children

“…Walsh et al (2015) reported that in short, simple sentence production (e.g., "buy bobby a puppy"), relative to their typically fluent 4-and 5-year-old peers, CWS lagged in speech motor coordination and in measures of basic kinematic parameters, such as articulatory speed. In addition, in an experimental paradigm identical to the one employed in the current study with sentences of varying length and complexity, 4-to 6-year-old CWS exhibited increased lip aperture variability (LAVar) compared to children who do not stutter (CWNS) for fluent productions (MacPherson & Smith, 2013). Such results suggest that CWS in the preschool years lag behind their peers in speech motor development.…”

“…We predicted that CWS-Per would likely exhibit higher LAVar, but not longer movement duration, compared to CWSRec and CWNS, on the basis of findings from previous studies (MacPherson & Smith, 2013;Walsh et al, 2015). We also hypothesized that increasing linguistic complexity would have a disproportionate effect on the speech motor systems of CWS-Per compared to our other two groups.…”

“…Previous findings from our laboratory suggest that both indices of language processing (e.g., Usler & Weber-Fox, 2015) and speech motor coordination (e.g., MacPherson & Smith, 2013) are atypical and immature in CWS compared to typically developing children. The demands of utterance length and syntactic complexity have also been correlated with the likelihood and loci of SLDs during speech production (Logan & Conture, 1995;Yaruss, 1999;Zackheim & Conture, 2003).…”

“…With parental consent, our participants were enrolled in the Institutional Review Board (IRB)-approved Purdue Stuttering Project; many had taken part in previous studies from our laboratory (e.g., MacPherson & Smith, 2013;Usler & Weber-Fox, 2015). For this greater project, children were followed longitudinally over a maximum of 5 years, during which time annual testing was conducted in as close to 12-month intervals as possible.…”

“…Stuttering has long been described as a disorder of speech motor discoordination and instability, with intervals of fluency and disfluency not observed as dichotomous phenomena, but instead as events along a continuum of speech motor coordination (Adams & Runyan, 1981;Van Riper, 1982;Zimmermann, Smith, & Hanley, 1981). Even when perceptually fluent, the speech of individuals who stutter has been associated with atypical speech motor coordination (Caruso, Abbs, & Gracco, 1988;McClean, 2004;McClean, Kroll, & Loftus, 1990;Zimmermann, 1980) and increased articulatory variability (Kleinow & Smith, 2000;MacPherson & Smith, 2013;Smith, Goffman, Sasisekaran, & Weber-Fox, 2012) compared to typically fluent controls. Adults who stutter (AWS) have exhibited atypical speech and nonspeech motor performance compared to their typical peers, specifically in coordination tasks between different motor components or effector systems (Forster & Webster, 2001;Zelaznik, Smith, Franz, & Ho, 1997).…”