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.
Oh, and I am a great speller, except I get my "ie" and "ei" rules backwards every time, never fails.
Being a southpaw myself, I can clear this up for you.
Everyone is born right-handed, however, only the few gifted individuals overcome that handicap... :-)
It's 'cause righties are spoiled. What's funny is watching then when they're temporarily incapacitated due to a broken arm or something and HAVE to be lefties! Hilarious!
My son is also left handed and right footed. When he was in pre-school, I was told that this might be a problem because psychologists have noted that reading problems and dyslexia are often found in cross-dominant left handers. This proved to be the case, although it was not diagnosed until high school. My son got all A's in grade school and it wasn't until high school that he started to slow down. He did always have atrocious handwriting, though. It turns out that he is dis-graphic and slightly dislexic. Now we realize that my husband is also. They just never idenified those things when we were kids. (My son broke his left wrist playing basketball and his handwriting wasn't any worse with his right hand).
The article said humans are the only primate--not the only species.
(For one thing, horses have a preference.)
Part of my job is giving directions to where we are located. It's know wonder half my appointments never show.
There is a reason for that. The dominant arm is on top so it can be used more quickly.
Along similar lines, I used to reach for objects with my left hand. That is my dominant hand, so no surprise. But then after about 30 years of cutting, burning, bruising, and otherwise putting my dominant hand into the circular saw blade, I decided to reach with my right hand so if something slipped I would be more likely to lop off useless fingers, etc on my retarded right hand than intelligent fingers from my left. As if it's important which hand I use to write illegibly, I use the left. I knew a master carpenter who had only 2 fingers on the right hand, 3 separate power saw accidents. Figured it was too late to give him advice.
When I first learned to write, I would use my right hand until it became tired, then I would switch to my left hand.
When my left hand began to tire, I would switch back again.
Seemed perfectly natural to me.
One day while the class was copying a lesson from the blackboard, the teacher patrolled the isle between our desks.
On her fourth circuit around the room, the teacher noticed I was using my right hand and asked me if I had been using my other hand a moment ago, or was she going crazy.
I write, eat, play pool, use scissors, swing a tennis racket, and probably other things, left handed...but I bat a ball, throw a ball, catch a ball, and use the mouse right handed...
When my firstborn child wanted to learn how to tie his shoes, I showed him how to tie a bow...he just could not get it, was getting frustrated, started crying, and I began to think he was either just slow on this, or not paying attention...then he said, it seemed backwards to him...and it dawned on me, that perhaps he needed to see a right handed person tie a bow...my hubby, who is right handed, was not at home, so I went to my neighbor, who was right handed and after she showed him one time how to tie a bow, he had it nailed down perfect...so when it came time for the younger boy to learn how to tie his shoes, I gave that job to his older brother...
When I first learned how to write cursive, I wrote what they call 'backhanded', that is, instead of my writing slanting to the right, it slanted to the left...the teachers could not stand it, and demanded that I write slanting to the right...to this day, I write slanting to the right....but if I am in a hurry, I revert back to my 'backhanded' ways...And I have to remind myself to write slanting to the right, its not a natural process...
Being left handed has never really been much of an inconvenience for me, altho I hate it when anyone hands me a charge card receipt to sign, or the Mailman has me sign for something...because they always present it to you as if you are right handed, and you must always turn it around...not a biggie mind you, but it just shows that they assume everyone is righthanded, when they are not...
The other inconvenience is whenever we go out in a group to a restaurant and sit at a booth...I must always sit on the outside because I eat left handed, and sitting next to a right handed eater, our arms always bump...
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