Stuttering is a speech disorder in which the normal flow of speech is disrupted by frequent repetitions or prolongations of speech sounds, syllables, or words, or by an individual's inability to start a word. The speech disruptions may be accompanied by rapid eye blinks, tremors of the lips and/or jaw or other struggle behaviors of the face or upper body that a person who stutters may use in an attempt to speak. Certain situations, such as speaking before a group of people or talking on the telephone, tend to make stuttering more severe, whereas other situations, such as singing or speaking alone, often improve fluency.
Stuttering may also be referred to as stammering, especially in England, and by a broader term, disfluent speech. Stuttering is different from two additional speech fluency disorders: cluttering, characterized by a rapid, irregular speech and spasmodic dysphonia, a voice disorder.
Speech is normally produced through a series of precisely coordinated muscle movements involving respiration (the breathing mechanism), phonation (the voicing mechanism) and articulation (throat, palate, tongue, lips and teeth). These muscle movements are initiated, coordinated and controlled by the brain and monitored through the senses of hearing and touch.
Before speaking, an individual takes a breath and the vocal folds (or vocal cords), which are two bands of muscular tissue located in the voice box directly above the trachea or windpipe, must come together. The air that is held in the lungs is gradually released, passing through the gently closed vocal folds thus causing vibration and producing the voice. The sound of the voice is passed through the throat and is directed into the mouth for most speech sounds, or into the nose for nasal sounds such as "m," "n" and "ng." The palate, tongue, jaw and lips move in precise ways to modify the sounds in order to make speech sounds.
It is estimated that over 3 million Americans stutter. Stuttering affects individuals of all ages but occurs most frequently in young children between the ages of 2 and 6 who are developing language. Boys are three times more likely to stutter than girls. Most children, however, outgrow their stuttering, and it is estimated that less than 1 percent of adults stutter.
Many individuals who stutter have become successful in careers that require public speaking. The list of individuals includes Winston Churchill, actress Marilyn Monroe, actors James Earl Jones, Bruce Willis, and Jimmy Stewart, and singer Carly Simon, to name only a few.
Scientists suspect a variety of causes. There is reason to believe that many forms of stuttering are genetically determined. The precise mechanisms causing stuttering are not understood.
The most common form of stuttering is thought to be developmental; that is, it occurs in children who are in the process of developing speech and language. This relaxed type of stuttering is thought to occur when a child's speech and language abilities are unable to meet his or her verbal demands. Stuttering happens when the child searches for the correct word. Developmental stuttering is usually outgrown.
Another common form of stuttering is neurogenic. Neurogenic disorders arise from signal problems between the brain and nerves or muscles. In neurogenic stuttering, the brain is unable to coordinate adequately the different components of the speech mechanism. Neurogenic stuttering may also occur following a stroke or other type of brain injury.
Other forms of stuttering are classified as psychogenic or originating in the mind or mental activity of the brain such as thought and reasoning. Whereas at one time the major cause of stuttering was thought to be psychogenic, this type of stuttering is now known to account for only a minority of the individuals who stutter. Although individuals who stutter may develop emotional problems such as fear of meeting new people or speaking on the telephone, these problems often result from stuttering rather than causing the stuttering. Psychogenic stuttering occasionally occurs in individuals who have some types of mental illness or individuals who have experienced severe mental stress or anguish.
Scientists and clinicians have long known that stuttering may run in families and that there is a strong possibility that some forms of stuttering are, in fact, hereditary. No gene or genes for stuttering, however, have yet been found.