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From: Hans-Georg Bosshardt
Date: 20 Oct 2005
Time: 02:17:47 -0500
Remote Name: 134.147.64.23
Hi Tom, I think that there is some information from Ehud Yairis work available to answer your question. About 41% of the parents of stuttering children report that their children suddenly began to stutter within up to three days and another group of 27% reported that their children gradually began to stutter over a period of 3- to 6 weeks. So, there is not always a strict border between fluency and disfluency or stuttering and the average age at suttering onset is shortly before the third birthday (34 months). At this age the language of most children is already quite elaborate. When stuttering begins at this age, children generally have already spoken without any obvious disfluencies or abnormalities. These facts do not contradict any of the explanations you mention in your question. The reason is that genetic dispositions are not always expressed in phenotype (i.e. in our case lead to stuttering) and are not expressed phenotypically without variation. Similarily, neuranotomical deficits or neurotransmitter imbalances can manifest themselves in overt behavior (i.e. stuttering) only under certain conditions of language complexity. Imagine that you test a used 8 cylinder car. You will probably not be able to detect a defect in one cylinder if you drive it with 30 km/h. But you have a good chance to detect this motor problem if you drive it 220km/h over a German highway. Greetings from Hans-Georg