New evidence that bimanual motor timing performance is not a significant factor in developmental stuttering

Stuttering is a disorder that involves a breakdown in the speech-motor system, resulting in disfluencies such as part- and whole-word repetitions, prolongations, and blocks. This study addresses the question regarding whether this motor breakdown is specific to the speech-motor system, or more generalized across motor systems. As an expansion 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 were followed for five years of the study by completing a clapping task using a synchronization-continuation paradigm. Two analyses were completed. The first was a cross-sectional analysis of the data from the children in the initial year of the study (ages 4;0-5;11) comparing clapping performance between CWS and CWNS. In the second longitudinal analysis, the data were organized by the children\u27s age to compare clapping performance across the developmental continuum, and compared by eventual persistence or recovery status of stuttering. The results of these analyses reveal that preschool CWS do not differ from their nonstuttering peers on rates of clapping, and are not more variable than typically developing peers in performance of a bimanual rhythmic timing task. Additionally, bimanual motor timing differences are not a likely candidate as a contributing factor to the eventual persistence or recovery from stuttering. From these findings, we conclude that a bimanual motor timing deficit is not a core feature of persistent developmental stuttering