Posted on 03/06/2002 9:50:08 PM PST by PurVirgo
Rense.comPeople who grow up left-handed have a different, more flexible brain structure than those born to take life by the right hand, say researchers at the University of California, Los Angeles, who used twins to study heredity.
The reason is that right-handers have genes that force their brains into a slightly more one- sided structure, according to research published yesterday in the Proceedings of the National Academy of Sciences. Left-handers appear to be missing those genes.
"There really is a difference in brains that results in a more symmetric brain in left-handers, where the two sides are more equal," said UCLA neurogeneticist Daniel Geschwind, who led the research team. "There is more flexibility, and that is under genetic control."
In the effort to understand how the brain shapes the mind, researchers have been striving to document the way genes and environment affect intelligence and mental abilities. The human insistence on preferring one hand over the other poses a particularly nagging question that touches on both anatomy and behavior.
"There is clearly something fundamental here we need to comprehend if we are to understand what makes us uniquely human," Geschwind said.
Of all the primates, only human beings display such a strong predisposition to right-handedness. Right-handers make up about 90 percent of the population. The left and right halves of the brain are different in both their anatomy and their functions, related in part to hand preference.
But until now, no one could document the connection.
The UCLA study is the strongest evidence yet that heredity shapes the brains of left-handed and right-handed people differently, Dartmouth neuroscientist Michael Gazzaniga said.
The UCLA researchers conducted brain scans on 72 pairs of male identical twins between 75 and 85 years old.
Identical twins, who share the same genes, offer a unique lens through which to study the relative effects of heredity on human nature.
Right- and left-handedness is partially determined by genetics. If a person inherits the gene for right-handedness, that person will be right-handed. People who do not have that gene, however, can be either left- or right-handed. There is no specific gene for left-handedness.
Right-handers typically have a larger left brain hemisphere, where their language abilities are concentrated.
Conversely, left-handers have more balanced brains, with both sides relatively symmetrical. The language abilities of left-handers more often are concentrated on the right side.
If identical twins carry the gene for hand preference, both must be right-handed. If they lack the gene, one twin can develop right-handed while the other develops left- handed.
The researchers found that the brains of identical right-handed twins were very similar in size and structure. But when a left-hander was part of the twin set, the brains were different. The conclusion, researchers said, is that the absence of the gene for hand preference allows the brain to develop differently as the individual grows up.
A similar pattern did not appear in 67 sets of fraternal twins used as a control group.
When she learned to read, she could read an upside-down book as fast as if it was right-side up.
Cross your arms over your chest. Know what I mean? Like you were cold or whatever. Generally one hand will lie on the opposite bicep and the other will tuck under. Most of the time, your dominant hand will be the one that's up.
I eat and write left handed but do almost everything else with my right hand.
I have noticed that some of the left handed people I know have trouble telling right from left. Is this a common thing among left handers?
LOL, I'm not sure I like your question but admit I have wondered the same thing. In addition to many left handed people I know that don't know right from left, it seems many of them were breech births also.
My 7 year old son is a lefty, I thought this was a little strange because nobody else on either side is.
My husband swears he can use either hand, although he's never shown me this, except he can use a mouse equally well with either hand. Maybe he simply doesn't have the righty gene and ended up a righty and my son inherited it from him but ended up lefty.
When she learned to read, she could read an upside-down book as fast as if it was right-side up.
I am the same way. When I write right-handed, it is mirror perfect and very legible. I can also read upside-down or mirror backwards without any problems. Very helpful when working on projects with people across the table!
One odd thing though... If I write with my right fingertip(on a dirty window or something), it comes out perfectly normal.
And for lefties: not only can you change the buttons on your mouse and use it on the left, but you can get lefty cursors. I found mine on tucows.com.
I myself am left-handed, and my oldest brother is left handed also. My two other brothers are righty's. It's funny, cuz you can really see some personality differences among us. Me and my oldest bro, along with my mom, are more cognitive, so to speak. It's hard to compare us with my youngest bro, b/c we have different fathers. But Jason (the one between) is very mechanically oriented, hell he's like a damn tinker gnome the way he can take things apart, figure out how they work, and put it back together perfectly. But me and Eric (the oldest), we like to know why they work. I eat and write with my left hand, and my good ear/eye are on the left, but when I play ball, I bat right, and kick right when I play soccer. When I read a magazine, I read it from back cover to front, and can often read better if I hold the book upside down. I can remember in school, and when I fill out paperwork, I go from bottom right to top left, instead of left to right, top to bottom.
I know ppl get aggravated when they need to use my desk, because everything is "backwards" from them. But I know that it is predominantly a right handed world. Scissors, housing/building designs, yes even soup ladles are designed for righties.
Don't know if it really means anything, but its an interesting thing to keep an eye out for...
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