Spring Break
Why are only 10 percent of people left-handed?
Faye Flam
Issue date: 11/16/07 Section: Science And Technology
In either form, this gene is active in the developing brain. "It influences the way different regions wire up and find connections," Francks says. Its effect on determining handedness is small, and the geneticist believes several yet-to-be discovered genes are also involved.
Environmental factors - stigma, social pressure, possibly hormones - could nudge people one way or the other as well.
Other scientists are examining how LRRTM1 and other genes might tie lefthandedness loosely with all sorts of characteristics. Various studies have found weak but statistically significant associations between lefthandedness and schizophrenia, autism and even homosexuality.
A few scientists say their colleagues are looking at the mystery of handedness from the wrong perspective.
University of Toledo psychologist Stephen Christman was trying to connect handedness with preference for types of musical instruments when he made an unexpected finding: people who were very strongly right- or lefthanded preferred keyboards and drums, while those who were more ambidextrous gravitated toward strings.
"I realized that maybe what's important is not left or right but strongly one-handed or mixed," he says.
There is some evidence, he says, that mixed-handers have a wider connecting pathway - called the corpus callosum - between the right and left hemispheres. Having a wider connection seems to make it harder to do more than one thing at a time - playing a different rhythm with each hand, for example.
Christman has found that strong right- or lefthanders, on the other hand, are more likely to hold to set beliefs, such as creationism. He speculates that communication between hemispheres helps people revise beliefs.
None of this suggests mixed-, right- or lefthanders have a corner on creativity or genius. Researching an essay on the lefty guitarist Jimi Hendrix, who famously played a righthanded guitar upside down, Christman made a shocking discovery: the much-photographed Hendrix held a pen with his right hand.
It makes sense, says Christman, himself a lefthanded guitarist, if you consider that in "righthanded" guitars, the left-hand job of working the frets has grown increasingly difficult as both styles and design have evolved.
So why not see how it works the other way around?
Environmental factors - stigma, social pressure, possibly hormones - could nudge people one way or the other as well.
Other scientists are examining how LRRTM1 and other genes might tie lefthandedness loosely with all sorts of characteristics. Various studies have found weak but statistically significant associations between lefthandedness and schizophrenia, autism and even homosexuality.
A few scientists say their colleagues are looking at the mystery of handedness from the wrong perspective.
University of Toledo psychologist Stephen Christman was trying to connect handedness with preference for types of musical instruments when he made an unexpected finding: people who were very strongly right- or lefthanded preferred keyboards and drums, while those who were more ambidextrous gravitated toward strings.
"I realized that maybe what's important is not left or right but strongly one-handed or mixed," he says.
There is some evidence, he says, that mixed-handers have a wider connecting pathway - called the corpus callosum - between the right and left hemispheres. Having a wider connection seems to make it harder to do more than one thing at a time - playing a different rhythm with each hand, for example.
Christman has found that strong right- or lefthanders, on the other hand, are more likely to hold to set beliefs, such as creationism. He speculates that communication between hemispheres helps people revise beliefs.
None of this suggests mixed-, right- or lefthanders have a corner on creativity or genius. Researching an essay on the lefty guitarist Jimi Hendrix, who famously played a righthanded guitar upside down, Christman made a shocking discovery: the much-photographed Hendrix held a pen with his right hand.
It makes sense, says Christman, himself a lefthanded guitarist, if you consider that in "righthanded" guitars, the left-hand job of working the frets has grown increasingly difficult as both styles and design have evolved.
So why not see how it works the other way around?
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Thomas Anderson
posted 8/16/09 @ 12:11 AM EST
Left-handedness appears to average around 20 percent among autistics, and is also very high among children with dyslexia and other learning problems. Some researchers have linked these problems to perinatal anoxia which suggests that left-handedness too might be a result of "brain damage" at the time of birth. (Continued…)
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