Left-Handedness - Brain Damage?

F. Frank LeFever flefever at ix.netcom.com
Sat Dec 21 16:07:57 EST 1996

<engelking-2012961128350001 at cust119.max18.san-francisco.ca.ms.uu.net>
engelking at earthlink.net writes: 
>I am a left-handed person and I have been recently reading up on the
>causes of my handednes.. Many of the reports I have read conclude that
>is caused by either trauma to the brain at birth, it is genetic, or
>it is a form of brain damage (!). What is the status of all these
>in the medical community? And also, do we left-handed people have any
>special right brain skills (visual-spatial I've read?)? What are the
>consequences of being left-handed? How do I differ from right-handers?
>engelking at earthlink.net

There is a concept of "pathological left-handedness" (Paul Satz et al.)
which MIGHT be relevant to SOME left-handers, but probably very few.  I
presented a paper at the International Neuropsychological Society
meeting in Innsbruck (June or July, 1990) describing identical twins
who BOTH had cerebral palsy, with right side more involved than left; 
they had very similar cognitive test profiles, and this profile was
arguably that expected in "pathogical left handedness", but only one
was left handed...

The theory is that very early left hemisphere damage impairs its normal
role in language development, requiring more participation of the right
hemisphere, to the detriment of traditional "right hemisphere"
nonverbal skills.

We really do not know much about what causes NORMAL left-handedness;
however, there is some familial tendency (very complicated, maybe
sex-linked?) and one idea I've come away with (mostly Jane Healey's
research) is that your brain organization for COGNITIVE things may be
more related to your parent(s)'s handedness than your own.

In any case, the correlates of handedness are so complex and so subtle,
one has to be uncertain about them in any individual case.

Frank LeFever
New York Neuropsychology Group

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