I too have a left-handed son and have wondered at how he learns some things so
easily and other things with difficulty. But there's a wide gap between my
personal wonder and understanding what differences there might be cognitively
between right-handers and left-handers.
A couple years ago, I audited some neurophysiology classes. I recall that
handedness is actually quite complex. Some left-handers hold their pens more
straight up because they are visually processing what they're writing with the
right side of their brains (like true left-handers). But other left-handers
hold their pens at a slant because they are visually processing what they are
writing with the left side of their brains (just like right handers).
Handedness is a function of the motor part of the brain, around the center
crown of the head. Visual processing touches upon many parts of the brain,
from the lower rear on both left and right hemispheres to more integrative
functions in the frontal cortex (again both sides).
One interesting and somewhat dated book applying the ideas of hemisphere
difference to visual processing is "Drawing with the Right Side of the Brain."
From a young age, I was always been able to draw with ease and accuracy (a
skill that runs in my family), and I found this book described the type of
processing I use to do this -- the key distinction is not looking at things as
verbal abstractions but looking at them as spatial entities and carefully
measuring the spatial relations as you observe and draw. I'm right-handed,
but I've always handled drawing in this more spatial way. No one ever had to
explain it to me. I just did it.
Anyway, I'm just suggesting that handedness is really just one job that the
brain is handling, and being dominant in one hand or the other (or ambi)
doesn't necessarily mean you are "artistic" or "logical" or anything else. It
means that's how your hands function. Those higher functions are handled by
other parts of the brain and the integration of these functions is quite
complex and varied. It's interesting to know how specialized the brain really
is -- how certain areas specialize in this tasks like matching printed word to
the correct sounds of spoken speech, or remembering faces, or regulating the
fluency of speech (how smoothly one speaks). Gender also apparently plays a
role since the connective element between the two sides of the brain (corpus
colossum) is larger in women than men, but again, the size itself might not be
the major factor here, but other factors that brain imaging hasn't even begun
to show us yet...
Louise