Understanding Sex Differences in Developmental Stuttering

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Re: Questions re: stuttering and sex differences

From: Dave Corey
Date: 11 Oct 2009
Time: 14:29:37 -0500
Remote Name: 98.163.237.149

Comments

Hi Monica and thanks for your questions. I don’t know of any convincing argument for an evolutionary explanation for sex differences in stuttering prevalence. I think that any such explanation would be subsidiary to the explanation of some more general sex difference. That is, I doubt that stuttering itself has been selected for by evolution. Similarly, I doubt that it was a pervasive condition that has been selected against by evolution. Rather, my guess is that some feature that has been selected differentially in males and females carries with it stuttering as an unwanted tagalong. Among fluent males and females, lateralization of language function to the left hemisphere is thought to be more complete in males than in females. A leftward asymmetry that corresponds to language lateralization is seen in a structure called planum temporale (PT). PT is auditory association cortex and includes much of the superior surface of the temporal lobe. Left PT is heavily involved in language production and comprehension and is thought to be than the right PT for this reason. Perhaps similarly, having language functions strongly left-lateralized is much more common in left- than right-handers. Whereas about 98% of right-handers are left-lateralized, only about 70% of left-handers are strongly left-lateralized. Oddly enough, the relative dispersion of language function seen in females is also seen in people who stutter. People who stutter are thus usually male but are more likely to represent language in the brain like females do. These are very superficial comments—there is a great deal of information in the literature on asymmetry of brain function, language lateralization and sex differences in both.


Last changed: 10/11/09