Stuttering is caused by poor connections between two areas in the left hemisphere of the brain, German researchers said recently. Although scientists knew that stuttering - the involuntary repetition of consonants, sounds or words - had a genetic link, how and why it occurs has remained a mystery. German scientists, using magnetic resonance (共振) imaging (MRI) to look into the brains of people who stutter, have uncovered new clues. “ Fibers between the speech area and language planning area of the brain seem to be disrupted ” , said Dr. Christian Bushel of the University of Hamburg. The disturbed timing in the speech-related areas in the brain causes the difficulty that usually begins between the ages of three and five and affects up to 7 percent of children and one percent of adult.