Stuttering, or stammering as it is also referred to, is a developmental speech disorder, which usually appears in children between the ages of 3 and 8 years. More often than not it remits before puberty, but it can persist into adult life. Stuttering is characterized by involuntary syllable repetitions, syllable prolongations, or interruptions (blocks) in the smooth flow of speech. There may sometimes be difficulty in differentiating infants who definitely stutter from those who show the dysfluency often seen in infancy as a normal stage of speech development. However, the two are distinct. The overall frequency of dysfluency, the proportion and duration of dysfluency types, and the associated behaviours not directly related to speech such as eye, head, and body movements, can help to distinguish between the two. There has certainly been controversy over the exact definition of stuttering when selecting participants for research studies. Wingate criticized Yairi and coworkers for not being strict enough in their selection of affected children and for including those who were classified as having stutter-like dysfluencies, especially whole-word repetitions. However, Yairi and colleagues refuted these claims, stating that although syllable repetitions are the most common component of stuttering, whole-word repetitions do occur in stuttering and therefore this is not a criteria for exclusion. In fact, whole-word repetitions seem to be more common when the onset of stuttering is early in life.