For example, while left-handed people make up only 10 percent of the population, 20 percent of schizophrenics are left-handed. And those who are ambidextrous (able to use both hands), only an estimated 1 percent of the total population, may be even more at risk; 30 percent of schizophrenics are ambidextrous.
However, the Wall Street Journal reports there is also good news for lefties of the world, (of which I am one):
On average there is no significant difference in IQ between righties and lefties, studies show, belying popular perceptions. There is some evidence that lefties are better at divergent thinking, or starting from existing knowledge to develop new concepts, which is considered an element of creativity.
And whatever their political persuasion, lefties are in good company: Six of the past 10 presidents, including both Barack Obama and George H.W. Bush, have been left-handed.
Still, left-handed people, perhaps owing to their greater artistic inclination, tend to earn about 10 percent less in annual salaries than their right-handed counterparts, according to a recent Harvard University study.
Doctors are still unable to determine what causes hand preference but are finding that environmental factors, particularly stress in the womb, may play a leading role:
Babies born to older mothers or at a lower birth weight are more likely to be lefties, for example. And mothers who were exposed to unusually high levels of stress during pregnancy are more likely to give birth to a left-handed child. A review of research, published in 2009 in the journal Neuropsychologia, estimated that about 25% of the variability in handedness is due to genetics.
People commonly say that left-handed people operate with the right side of their brain, while right-handed people use the left side. And to some extent, that's not only proving to be true, but may also explain why lefties are slightly more prone to psychological disorders:
Some 70% of lefties rely on the left hemisphere for their language centers, a key brain function, says Metten Somers, a psychiatrist and researcher who studies brain lateralization at Utrecht University Medical Center in the Netherlands. This doesn't appear to present problems, scientists say. The other 30% of lefties appear to exhibit either a right-dominant or distributed pattern, Dr. Somers says. They may be more prone to impaired learning or functioning, and at greater risk for brain disorders, he says.
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