Study Shows Left-Handers Have More Flexible Brains

http://www.rense.com ^ | 3-6-02 | Robert Lee Hotz

[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.

[PurVirgo]

I think there a couple of interesting arguments that can go either way. Like, if the gene for right-handedness is inhereted, and there is no gene for left-handedness, why do those that lack the gene prefer the left hand? After all, humans learn by mimicry.

Secondly, how is it that humans are the only species with a gene for hand preference? (I think that's neat myself)

Dunno, I think it goes beyond writing, which is mostly training and practice.

Does the ambidextrous person, who is mostly "right handed" exhibit the same kind of brain development also? What about the "left handed" person who is forced to use their right hand? Is their brain development the same as a right handed person?

[diefree]

My daughter is left-handed. Her Italian grandmother tried to get me to force her to be right-handed. After all, the Italian word for left is sinister.

She eats with her left hand but seems to do everything else with her right hand. She has a very quick mind, one of the best arguers I have ever known, but I don't know if being left-handed would have anything to do with it, as my younger daughter, who is right-handed is becoming a pretty good debater herself.

[stands2reason]

I know left-handedness is particularly a male trait; strange considering as this article says there is no specific gene for it. Another question raised there. I wonder if left-handedness can also be a result of brain damage? The mentally retarded also have a higher instance of left-handedness.

[stands2reason]

It's a good thing you didn't force her; doing so can cause stuttering I've heard (something to do with the cross-wiring of the language center of the brain) among other problems. My father tried to force me, but it didn't take too well. Still a lefty, though I'm right-eyed and eared.

[Blowtorch]

Famous Left-Handers

[truth_seeker]

Left-handed people seem to be more artistic, and creative, based solely on my life experience.

Twice I broke my right hand, and was forced for a few weeks to become a leftie. It has made me more towards ambedextrous, which came fairly easily. In tests I consistently score evenly between language and quantitative. Are those things related?

My father was much the same, and also experienced several hand injuries. While right handed, he was very artistic and creative. Do we carry something akin to a propensity (gene) towards being ambedextrous, but are trained to select right-handedness?

[UCANSEE2]

If the left side of the brain controls the right side of the body, and the right side of the brain controls the left side of the body,
then only left-handed people are in their right mind.

[UCANSEE2]

If the left side of the brain controls the right side of the body, and the right side of the brain controls the left side of the body,
then only left-handed people are in their right mind.

[1FreeAmerican]

Oh my god- you've just explained my whole screwed-up life to me- I'm retarted!!

[1FreeAmerican]

And I can't type very well either!!

[sonjay]

I wonder if left-handedness can also be a result of brain damage? The mentally retarded also have a higher instance of left-handedness.

Probably not brain damage. I have read (sorry, I don't have cites handy, but in numerous sources over the years) that left-handers are disproportionately represented among the insane, geniuses and criminals. Interesting mix, there.

The Boston Strangler and Jack the Ripper were left-handed, as were many other infamous criminals. Some years ago (1996? 1992?) all three presidential candidates were left-handed. Of course, politicians might be considered to among the criminal class. Allowing my flexible, left-handed brain to wander a bit with this information, I begin to ponder sexuality preferences. If there's a gene that causes right-handedness, and missing that gene means the person can "go either way," could there also be such a gene for sexuality? I.e., people born with the "straight" gene grow up straight, and those missing it can "go either way."

The article also said that left-handers (those missing the LH gene) tend to have more flexibility between the two sides of the brain; a similar sexuality gene could explain those who "go both ways" sexually.

(No flames, please; I'm not trying to promote any sexual agenda here and am firmly hetero myself, just pondering possiblities.)

[laredo44]

sorry, I don't have cites handy

I'm guessing the pun was unintended.

[RightOnline]

I'm VERY left-handed, as are 3 of my 7 children (don't know about the 5-month-old yet; too early to tell). However, I eat right-handed and play guitar right-handed. Other than that.............forget it.

Interestingly, if you walk into a typical office full of computer types and do a little, informal poll, you'll find that fully 40% of them will be left-handed. Try it; you'll see what I mean.

[laredo44]

Does anyone know the term for having a different hand preference for different tasks, as contrasted to ambidextrous, meaning performing a task with either hand with equal proficiency? Some personal examples: write/left hand, kick/left foot, throw/right hand, eat/right hand, brush teeth/left hand, and so on. I know there's a term for this behavior but have forgotten it.

[Judith Anne]

Interesting. I was left-handed, forced to change in school...I can write either right or left handed, but its easier to write "mirror" style with my left hand...I didn't stutter, but had great difficulty with b's and d's, q's and p's, and when very young, thought E and 3 were the same thing...I still say "left" sometimes when I mean "right."

[Betteboop]

bump

[Rustynailww]

bill clinton is left handed.

[Madame Dufarge]

I know there's a term for this behavior but have forgotten it.

"Confusion." I exhibit it too.

I also hold playing cards upside down. Go figure.

[Judith Anne]

Well, Bill was going to be right-handed, like most people, or left-handed, like some people, or one-handed, like a few people or no-handed, like a very few people.

I think he's sinister, myself. ;-D

[Jhensy]

Well, I'm definitely a lefty; I write, eat, bat, brush my teeth, etc. from the left. BUT, I throw righty, kick righty, golf righty, and most amazingly to me, work the mouse righty even though I write lefty.

You'd say "ambidextrous", but if I try to do these things the opposite, I can't do them. If I try to write righty, it looks like the usual chicken scratch; I throw lefty like a 7-year-old.

As for lefties being artistically creative, in addition to being lefty, I'm also a Libra, which supposedly is the most creative of the zodiac signs. My profession? Designer/artist.