Purpose: Stuttering involves a breakdown in the speech motor system. We address whether stuttering in its early stage is specific to the speech motor system or whether its impact is observable across motor systems. Method: As an extension of Olander, Smith, and Zelaznik (2010), we measured bimanual motor timing performance in 115 children: 70 children who stutter (CWS) and 45 children who do not stutter (CWNS). The children repeated the clapping task yearly for up to 5 years. We used a synchronization-continuation rhythmic timing paradigm. Two analyses were completed: a cross-sectional analysis of data from the children in the initial year of the study (ages 4;0 [years;months] to 5;11) compared clapping performance between CWS and CWNS. A second, multiyear analysis assessed clapping behavior across the ages 3;5-9;5 to examine any potential relationship between clapping performance and eventual persistence or recovery of stuttering. Results: Preschool CWS were not different from CWNS on rates of clapping or variability in interclap interval. In addition, no relationship was found between bimanual motor timing performance and eventual persistence in or recovery from stuttering. The disparity between the present findings for preschoolers and those of Olander et al. (2010) most likely arises from the smaller sample size used in the earlier study. Conclusion: From the current findings, on the basis of data from relatively large samples of stuttering and nonstuttering children tested over multiple years, we conclude that a bimanual motor timing deficit is not a core feature of early developmental stuttering. Stuttering is a speech production disorder characterized by disfluencies such as part-word repetitions, prolongations, and silent blocks. The etiology involves multiple factors, including motoric, linguistic, and psychosocial contributors (Conture, 1990;Smith, 1990;Starkweather, 1993;Van Riper, 1982;Wall & Myers, 1995). Stuttering onset generally occurs around 2-5 years of age with a 75% recovery rate for children who began to stutter in these years Watkins, Yairi, & Ambrose, 1999;. Stutter-like disfluencies result from disruptions in the neural commands to the muscles necessary for fluent speech (e.g., Smith, 1989). These motor disruptions are observed in articulatory, laryngeal, and respiratory systems (Kleinow & Smith, 2000;Max & Gracco, 2005;Max, Guenther, Gracco, Ghosh, & Wallace, 2004;McClean & Runyan, 2000;Peters & Boves, 1988;Smith, 1989;Ward, 1997;Zimmermann, 1980). There is also evidence, though mixed, that children and adults who stutter (CWS and AWS, respectively) show less proficiency in nonspeech motor tasks (Brown, Zimmermann, Linville, & Hegmann, 1990;Caruso, Abbs, & Gracco, 1988;Cooper & Allen, 1977;Falk, Müller, & Bella, 2014;Forster & Webster, 2001;Howell, Au-Yeung, & Rustin, 1997;Max, Caruso, & Gracco, 2003;Neef et al., 2011;Olander, Smith, & Zelaznik, 2010;Ward, 1997;Webster, 1986;Westphal, 1933;Zelaznik, Smith, Franz, & Ho, 1997).Extending the work of Olander et al. (2010), who found a large ...

A study was conducted to examine production variability in American Sign Language (ASL) in order to gain insight into the development of motor control in a language produced in another modality. Production variability was characterized through the spatiotemporal index (STI), which represents production stability in whole utterances and is a function of variability in effector displacement waveforms (Smith et al., 1995). Motion capture apparatus was used to acquire wrist displacement data across a set of eight target signs embedded in carrier phrases. The STI values of Deaf signers and hearing learners at three different ASL experience levels were compared to determine whether production stability varied as a function of time spent acquiring ASL. We hypothesized that lower production stability as indexed by the STI would be evident for beginning ASL learners, indicating greater production variability, with variability decreasing as ASL language experience increased. As predicted, Deaf signers showed significantly lower STI values than the hearing learners, suggesting that stability of production is indeed characteristic of increased ASL

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Purpose In this study, we investigated how the direction and timing of a perturbation in voice pitch auditory feedback during phrasal production modulated the magnitude and latency of the pitch-shift reflex as well as the scaling of acoustic production of anticipatory intonation targets for phrasal prominence and boundary. Method Brief pitch auditory feedback perturbations (±200 cents for 200-ms duration) were applied during the production of a target phrase on the first or the second word of the phrase. To replicate previous work, we first measured the magnitude and latency of the pitch-shift reflex as a function of the direction and timing of the perturbation within the phrase. As a novel approach, we also measured the adjustment in the production of the phrase-final prominent word as a function of perturbation direction and timing by extracting the acoustic correlates of pitch, loudness, and duration. Results The pitch-shift reflex was greater in magnitude after perturbations on the first word of the phrase, replicating the results from Mandarin speakers in an American English–speaking population. Additionally, the production of the phrase-final prominent word was acoustically enhanced (lengthened vowel duration and increased intensity and fundamental frequency) after perturbations earlier in the phrase, but more so after perturbations on the first word in the phrase. Conclusion The timing of the pitch perturbation within the phrase modulated both the magnitude of the pitch-shift reflex and the production of the prominent word, supporting our hypothesis that speakers use auditory feedback to correct for immediate production errors and to scale anticipatory intonation targets during phrasal production.