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Path: utzoo!linus!faron!sidney
From: sidney@faron.UUCP (Sidney Markowitz)
Newsgroups: net.kids,net.med
Subject: Re: Changing Left-handedness to Right-handedness
Message-ID: <329@faron.UUCP>
Date: Thu, 15-Aug-85 11:26:59 EDT
Article-I.D.: faron.329
Posted: Thu Aug 15 11:26:59 1985
Date-Received: Sun, 18-Aug-85 22:38:37 EDT
References: <1076@ihlpg.UUCP> <29639@lanl.ARPA>
Reply-To: sidney@faron.UUCP (Sidney Markowitz)
Organization: The MITRE Corporation, Bedford, MA
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Xref: linus net.kids:1544 net.med:1855

[replace this line with your bug]

The 16 August 85 issue of "Science" has an article titled "The Brain
Connection: The Corpus Callosum is Larger in Left-Handers" on pg 665.
The corpus collosum, the portion of the brain that connects the two
hemispheres, is an average of 11% larger in left-handed and
ambidextrous people than it is in right-handers. What does this mean?
Well, besides the interesting speculations regarding the need for more
cross-hemispheric activity because of less segregation of functions
according to hemisphere, there's the following quote from the article,
discussing possible mechanisms for the difference in size, attributing
it to a *reduction* in the initial number of neurons that occurs in
the righties, but to a lesser degree in the lefties:

        Elimination of callosal collaterals has been suggested
        to underlie this decrease in fiber number and to be
        completed soon after birth. If more fibers do exist in
        the larger callosa of mixed-handers, the neuroanatomical
        difference between hand-groups may be related at least
        in part to axonal elimination, which occurs prior to most
        environmental influences.

In other words, handedness appears to be related to details of the
brain structure which are fixed shortly after birth. It doesn't make
much sense to try and train a kid to be a righty.

By the way, a disproportionate number of mathematicians and computer
scientists (especially those that are female) are left-handed, and of
professional musicians (especially the more successful) are
ambidexterous. 

					Sidney Markowitz

ARPA:	sidney@mitre-bedford
UUCP:	...{allegra,decvax,genrad,ihnp4,philabs,security,utzoo}!linus!sidney



-- 
					Sidney Markowitz

ARPA:	sidney@mitre-bedford
UUCP:	...{allegra,decvax,genrad,ihnp4,philabs,security,utzoo}!linus!sidney