Why some can't tell left from right

By Brian Alexander

At some point most of us confuse left and right like we’re in a scene from
an old Three Stooges one-reeler: “The one in your left hand!” “No, your
other left!” Bonk!

It seems silly. After all, it’s not like we’re new to the concept; we’ve
been using our left and right hands all our lives. Yet we sometimes flub --
some of us more often than others.

I’m not referring to people who’ve had strokes or suffered some other
injury or illness. Then there’s often a clear explanation for what
neuroscientists call “left-right confusion.”

But in 1978, researchers polled 364 university faculty, none of whom had
any known neurological problems, and all of whom would seem to be smarter
than the Three Stooges. It turned out that left-right confusion was common,
especially among the women. The question was, why?

It’s now 34 years later and, said Eric Chudler, director of the Center for
Sensorimotor Neural Engineering at the University of Washington, whose work
depends on knowing left from right, “that’s a difficult question. I don’t
know if any answer exists.”

According to M.K. Holder, executive director of the Handedness Research
Institute, and an adjunct assistant professor of psychological and brain
sciences at Indiana University, the link between brain “lateralization” --
the way specific functions appear to reside in left or right sides of our
brains -- and handedness (or even what we mean when we say “handedness”) is
still unclear.

But there does appear to be a link between degree of lateralization and
confusion.

For example, left-right confusion may be related to spatial reasoning. If
so, it might help explain why it’s more common in women than men; as a
group, women tend to underperform on a critical test of spatial reasoning,
called mental rotation, that requires subjects to mentally rotate images to
tell if they’re identical or mirror images of each other.

In 2011, though, a team of German scientists disputed that connection by
testing men and women who were matched in mental rotation ability before
subjecting them to two standard tests of left-right confusion. (The tests
require people to make a quick decision in response to directional words or
symbols.) Their report, which appeared in Brain and Cognition, found that
“matched participants showed robust sex differences in favor of men in all
[left-right confusion] measurements. This suggests that pronounced sex
differences…are a genuine phenomenon that exists independently of sex
differences in mental rotation.”

The degree of asymmetry of one’s brain hemispheres, or the degree of
lateralization, may be important. In 2009, British scientists found that
those whose hearing was more biased toward one ear over another, a sign of
asymmetry, were more likely to display confusion. Still, there’s no
definitive answer yet.

Meanwhile, if you’d like to test your own degree of left-right confusion,
Chudler has a test on his
website<http://faculty.washington.edu/chudler/java/hands1.html>.


*Brian Alexander (www.BrianRAlexander.com <http://www.brianralexander.com/>)
is co-author, with Larry Young PhD., of "The Chemistry Between Us: Love Sex
and the Science of Attraction," to be published Sept. 13.*


-- 
-Laye
==============================
"With fair speech thou might have thy will,
With it thou might thy self spoil."
--The R.M


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