Psychology of Left Handed People

Do you know that Left Handed people are more likely to have an IQ of over 131!

What do Barack Obama, Jay Leno, Michelangelo, Oprah Winfrey, Larry Bird and Jimi Hendrix have in common? They're all left-handed. Anywhere from 5% to 26% of the population are left-handed, but no one knows exactly why being left-handed is less common. A new review by Germany researchers looks at the current science behind left-handedness.

In assessing recent research on handedness, authors reached several conclusions. As with eye color and widow's peaks, handedness may be partly hereditary: Left-handers are more likely to have a left-handed parent.

In a smaller number of cases, left-handedness may also be the result of a genetic mutation or developmental defect. For example, left-handedness is 1.2 to 2 times more common in schizophrenics. People suffering from epilepsy, dyslexia and autism may also be more likely to be left-handed. Left-handedness is also more common in people born in spring or early summer, and that may be because higher rates of viral infections in moms-to-be during winter months might influence brain development.

"A possible explanation for the more common prevalence of certain diseases among left-handers may be due to intrauterine or perinatal disturbances, such as infections," said lead study author Stefan Gutwinski, M.D., of Berlin's Center for Integrative Life Sciences, in an email. "The development of the left cerebral hemisphere — which probably takes longer to mature than the right hemisphere — might be affected in other phases of brain development. This would result in a transfer of motor functions from the otherwise dominant left hemisphere to the right hemisphere, leading to left-handedness."

Some research even suggests that left-handers may have a shorter lifespan, possibly because of higher accident rates (most machines and emergency buttons are geared for right-handers) or a higher rate of certain diseases.

On the upside, left-handers are apt to be better at using both parts of their brain, as they tend to have a larger corpus callosum (the thick band of nerves that separates the right and left brain hemispheres). "Greater interhemispheric connectivity in left-handers might account for the reported findings that left-handers are more likely to have an IQ score above 131 and to have exceptional mathematical ability," said Dr. Gutwinksi.

Left-handers are better at using both hands at once, and that may partly explain why it's more common for them to be proficient musicians or professional athletes. Left-handers may also be more creative problem solvers as because of a tendency towards more connectivity between brain hemispheres.

But the question still remains unanswered: Why are more people right-handed than left-handed? If neither right- nor left-handed people have a clear evolutionary advantage over the other, it seems there should be a 50:50 ratio of handedness in the population. Maybe it's simply evolution's way of ensuring that less of us bump elbows at the dinner table.