Researchers have, for the first time, identified three genetic mutations that they believe are related to stuttering(どもる), a speech disorder involving hesitations and involuntary repetitions of certain sounds. The findings suggest that the problem has biological rather than emotional or social origins. The mutations were found in brain cells located in a speech center of the brain and affect a cellular process involved in degrading things the cells no longer need. Experts hope the finding will help them identify other genes involved in stuttering and allow them to better diagnose and treat stutterers.