Influences of sentence length complexity on the speech motor control of children who stutter

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, whereas that of CWS remained at the high level demonstrated for simple sentences. There was a trend for higher overall coordination variability in CWS compared with CTD. For both groups, movement duration was greater for syntactically complex, as compared with simple, sentences. Conclusions: Results indicate more variable speech motor coordination during fluent speech production in many CWS as compared with CTD. Disproportionate effects of length and complexity on coordination variability and duration were not found for CWS. Considerable individual differences in performance were observed. Key Words: stuttering, speech motor control, linguistic demands, articulatory coordination, syntax, fluency