Stuttering

Stuttering or stammering is a problem of speech. It is a speech disorder some people have. Five to six percent of children have a stammer while one percent of adults have a stammer. Men are four times more likely to have a stammer than women. Stammers normally start at 2-6 years and run in families. 
The person knows what they want to say but the flow of their speech is ‘bumpy’ and may have some of the following features:
Feelings and attitudes.
Stammering can be very upsetting, and knock a person's confidence. Joseph Sheehan compared stuttering to an iceberg, with the bumpy parts you can hear (overt parts) of stuttering above the waterline, and the larger block of how the person feels (covert parts) invisible below the surface. These people may feel embarrassment, shame, frustration, fear, anger, and guilt. These feelings may increase stress and effort making the person stammer more. Such negative feelings may be an important part of a treatment program.
Stammers affect peoples lives. They may lack confidence to apply for job interviews or make friends.
Treatment.
Stuttering therapy
Fluency shaping therapy.
This therapy is also known as "speak more fluently", "prolonged speech" or "connected speech." It trains stutterers to speak fluently (without the ‘bumpy bits’) by controlling their breathing and how they move their lips, jaw, and tongue.
Stutterers are trained to slow down their speaking rate by stretching vowels and consonants. Other methods include soft speech contacts. This helps to make very slow but non bumpy speech used only in the speech clinic. To make more normal sounding speech for daily life speed of speech is increased. Many people find their speech does not sound natural at the end of therapy. Fluency shaping approaches are normally taught in groups therapy programs, which may take two to three weeks to complete. More recently the Camperdown program, using a much shorter schedule, has been shown to work well.
Stuttering modification therapy.
The goal of stuttering modification therapy is not to get rid of stuttering but to change it so that stuttering is easier and less stressful. As fear and worry make people stutter by getting rid of these feelings stuttering will decrease. The most widely known approach was made by Charles Van Riper in 1973 and is also known as block modification therapy. Stuttering modification therapy has four stages: 
Famous stutterers.
There were many famous "stutterers":
Evolutionary note.
Features developed later in evolution are usually more variable than features developed earlier. The classic example of this principle is the difficulties of many human births compared to the reliability of ape births. Languages in hominids is certainly one of their later accomplishments.