Most experts believe that stuttering comes from a combination of biological and environmental factors. Stuttering does run in families, which indicates some neurological and genetic causes. If one identical twin stutters, there’s a greater chance that the other twin will become a stutterer.
Peter Wolson, a psychoanalyst, considers psychological and social reasons for stuttering. He thinks some cases of stuttering arise from internal conflicts due to family influences.
Both of these theories are compelling. I still think we’ll need years of research before cracking down on the exact mechanisms that lead to stuttering. In the meantime, if you have a child who stutters, bring him or her to visit a speech-language pathologist for counseling before the stuttering too strongly affects his or her social well-being.