Stuttering is defined as dysfluencies in speech including wholeand part-word repetitions, sound and syllable prolongations, and silent or audible blocking (i.e., inability to move lips and/or vocal folds to produce meaningful sounds). Fluent speakers exhibit 3% or less stuttered syllables (Caron & Ladouceur, 1989); therefore, a diagnosis of stuttering would not be appropriate unless the individual exceeds this level. Specifically, the formal diagnosis is based on an evaluation of oral reading and/or speaking that includes the determination of the percentage of stuttered words or syllables, the average duration of the stuttered events, and evidence of nonspeech sounds and physical concomitants such as facial grimaces, head movements, and movements of the extremities (Bray & Kehle, 1996).

The prevalence rate for stuttering is approximately 1% of the population, ...