Stuttering affects about 1% of adults. It is a speech disorder characterized by involuntary repetitions of syllables or words, prolongation of sounds, or blocks. It may also be accompanied by secondary behaviours such as closing the eyes or contracting facial muscles. Stuttering affects the motor aspect of speech: the person knows what he or she wants to say but has difficulty getting the words out. Stuttering is more common in men than in women: there are about four men for every woman who stutters. It also has a significant genetic component.
