Study Suggests Right-
Handedness Is Gene-Based
NEW YORK (Reuters Health) - A new study of twins bolsters the
belief that there may be a gene that distinguishes righties from
lefties, and perhaps influences the structure and function of
their brains as well.
California researchers examined 72 pairs of identical twins, who
share all of the same genes, and 67 pairs of fraternal twins, who
share many but not all genes. All were World War II veterans enrolled
in a long-term government brain study, and their average age was
72. All patients underwent MRI scans to compare the sizes of the
left and right sides of their brains.
The scans indicated that righties had less symmetrical brains
than the lefties, as has been shown in previous research, Dr.
Daniel Geschwind and colleagues report in the March 5th issue
of the Proceedings of the National Academy of Sciences.
And when the researchers compared individual pairs of identical
and fraternal twins, they found that the brains of the right-handed
identical siblings were the most similar structurally, suggesting
a strong genetic underpinning to right-handedness that does not
seem to be present for left-handedness.
"The brain structure differences in right-handers seem to have
a significant genetic component," said Geschwind, director of
the neurogenetics program at University of California, Los Angeles.
"We've shown this for the first time."
Geschwind told Reuters Health that previous studies have found
that nearly all right-handers have language function based in
the left side of the brain. But this is only the case in about
60% of lefties; the others have language function based in the
right half of the brain or shared between the two.
Studies also have indicated that while many lefties are gifted
at mathematics, architecture and music, they also tend to be more
likely to have stuttering problems, dyslexia and autism, Geschwind
"Being left-handed clearly has many advantages," he said. "It
can also reflect a greater susceptibility to language-based learning
As a result, studies like this one are important for researchers
trying to understand how left- or right-handedness relates to
brain functioning and for those hoping to develop new therapies
for speech disorders, he said.
SOURCE: Proceedings of the National Academy of Sciences 2002;99:3176-
Reference Source 89