Usually, stuttering appears slightly before adolescence, and sometimes it disappears after puberty. However, if it continues to a mature age, it usually stays forever. It is three times more likely for boys than girls to get this disorder. Stuttering can be treated through speech therapy, but the results vary. Most commonly, the problems can be decreased, but there is no objective way to measure the results.
Stuttering sometimes develops into blocking, that is, even the first letter or syllable becomes impossible to pronounce, i.e. blocked. A natural explanation for this is that while trying to avoid stuttering or in fear of stuttering, the person cannot utter the word at all. This too is an involuntary action, even though the development from stuttering to blocks can be partly intentional.
In the past, this disorder was often attributed to psychological problems, but perhaps the most prominent current view is that stuttering is caused by neural synchronisation problems in the brain. Recent research indicate that stuttering is correlated with disrupted fibres between the speech area and language planning area, both in the left hemisphere. This disruption could have been caused by early brain damage or a genetic link.
The disorder can be compared with dyslexia which is another disorder affecting communication.
Famous people who stuttered:
Warner Brothers animated character, Porky Pig and Ken Pile in A Fish Called Wanda, played by Michael Palin, who has done a considerable amount of work to support charites which work to help people who stutter.
As a practical note for non-stuttering people: most people stuttering would wish that the problem be ignored in normal situations. However, if stuttering causes a problem for the listener, then one should not be afraid to talk about it.