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From: Ken St. Louis
Date: 03 Oct 2010
Time: 14:43:08 -0500
Remote Name: 157.182.15.31
Dear Sachin, Good question. I'm not an expert on genetics, and maybe Dennis Drayna will weigh in here. Yairi and others have been suggesting that about half of those who stutter most likely have some documented genetic influence. About half do not. But that does not mean that the latter half have environmental causes. It is possible for people to have subtle physiological changes that are not genetic and not, strictly speaking, environmental. My best guess is that those stutterers for whom genetic links are absent most likely have some neuromotor differences that are determined by other factors. Some of those might be subtle brain damage at birth (as Per Alm suggests), neurochemical differences due to such factors as diet, or even changes in the brain due to environmental trauma. All this is not to say that parental expectations or very high speech standards or various types of psychopathology cannot cause stuttering, but these are probably quite rare. That's my take. Others may disagree. Ken