Happy Left-Handers’ Day! What Science Says About Handedness

It's a day to celebrate the 10% who always feel they're being elbowed out by the other 90%

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PhotoAlto / Michele Constantini / Getty Images

Left-handed? Today is your day — International Left-Handers’ Day, that is — a day to celebrate the 10% who always feel they’re being elbowed out by the other 90%.

While the body is remarkably symmetrical in many ways, in some key areas, it’s decidedly one-sided. About 10% of people are left-handed, a proportion that, for whatever reason, has remained relatively stable throughout human history (scientists have even determined that some cave painters etched their masterpieces with their left hands).

People who study the brain, and early development, have a number of theories about what drives handedness, but are at a loss to explain why humans are the only species with handedness. One theory holds that hand dominance is established in the womb by the hand that babies prefer hold to their mouths, while another says higher testosterone in utero can increase the chances of becoming a lefty.

But regardless of what sets the pattern, handedness can play a role in how we think, behave and interact with others. The brain, after all, is asymmetrical, with many thinking and intellectual skills centered in the left hemisphere, while emotional and mood-related functions are concentrated in the right. Some studies, for example, find that left-handed people tend to be more vulnerable to negative emotions such as depression and anger, possibly because southpaws, as they’re known, engage the right sides of their brains more actively.

(MORE: Are You a Hyperpolyglot? The Secrets of Language Superlearners)

An interesting trial published earlier this year even showed that right-handed people who clenched their right fists before memorizing a group of words, thereby activating the left sides of their brains, performed better on recall tests than right-handers who balled their left hands into a fist (in righties, the left side is home to the regions responsible for encoding information, and the right for recall).

Scientists have also found that lefties may be more prone to fear than righties, and therefore may be vulnerable to posttraumatic stress disorder.

Clearly, these associations aren’t absolute — otherwise no left-handers would ever jump out of a plane or brave New York City streets as a taxi driver. But scientists have found that left-handers have more symmetry between the right and left sides of their brains compared with right-handers. And that can have implications for everything from language to motor skills.

“The majority of people who are right-handed are left-hemisphere language dominant,” says Dr. Daniel Geschwind, a professor of neurology, psychiatry and human genetics at the University of California, Los Angeles. That means most of their language processing occurs in the left side of the brain.

“Almost 10% of [left-handers] have that flipped, and have right-hemisphere language dominance, and many have almost equal distribution of language skills in both hemispheres,” Geschwind says. “The notion is that left-handers are less constrained when it comes to brain asymmetry, so their skills are most randomized and less specified” to one side of the brain or the other.

(MORE: Brain Science: Does Being Left-Handed Make You Angry?)

That can have advantages, particularly after a stroke. Right-handed patients who have a stroke on the left side of the brain tend to recover their speaking abilities more slowly than left-handers, since they don’t have the wider distribution of language networks throughout both sides of the brain.

But there’s also a reason why left-handedness isn’t more common, even if it provides such advantages.

“Having more distributed language abilities probably makes the system more complicated, so it may increase the susceptibility to developmental [abnormalities] and neurodevelopmental disorders,” says Geschwind. That could explain some studies that correlated risk of autism, ADHD and dyslexia with being left-handed or with being ambidextrous.

So which comes first? Does being left-handed contribute to a different organization of the brain that makes it less asymmetrical, or does the brain’s layout veer someone toward left- or right-handedness?

“It’s fundamentally related, but it’s more like it happens together,” says Geschwind. “Left-handedness is a marker for how the brain is organized in a more symmetric than less symmetric way.”

Appreciating how that lack of symmetry translates into benefits — among high test scorers at Massachusetts Institute of Technology, for example, about 22% are lefties, which is double their proportion of the population — or risks is still a work in progress.

Which means that, in the meantime, lefties should celebrate their differences — or, in the case of their brains, the lack of difference between their right and left sides.

37 comments
8pandapassion8
8pandapassion8

i can never play tennis because my brain can never decide if its more comfortable by holding the racket in my left hand or right hand.....

I always write with my right hand, i just cant write with my left... but everything else, and i mean EVERYTHING, is with my left. I kick a soccer ball with my left leg, etc...

does that still mean i am anbidextrous?

AriadneEtienne
AriadneEtienne

The only thing I do with my right hand is write and use hand tools, everything else I do I'm left handed, including golf, baseball and playing guitar.  What does this mean?

RobertDeffenbaugh
RobertDeffenbaugh

I'm left handed and right but due to the fact that I write with my right I need to practice with my left.

VerIlao
VerIlao

im an ambidextrous man.i am writing with my right hand but do the hard or heavy tasks with my left hand.im a practical shooter and im using my left hand to shoot..

Sapphire19a
Sapphire19a

Interesting. What a disadvantage I had at school, where pupils had to write with fountain pens.  It took me most of the year to figure out why I was the only one with ink smudges all over the words I had written !!!

RoyStone
RoyStone

There is another dimension to this, or perhaps  two; being left dominant with   dyslexia and   the absence of vision in one eye due to a birth defect. Talking about confusing the perceptions and interpretations that go to the brain, and both  not being observed , diagnosed  or confirmed  until in early teens.  Hold your own "lefties"

GeraldZuckier
GeraldZuckier

Left Gifted, Bidextrous, and Transhanded people unite.

TimBeau
TimBeau

Anyone who has worked with dogs in flyball knows that the statement here that only humans have handedness is not true. When dogs turn on the box, they either turn right or left, and in training we do various exercises to see which the dog prefers before teaching them the turns.

mailman
mailman

HAPPY BIRTHDAY LEFT HANDERS,, IN THE 1990`S THE  RICHMOND VA BRAVES HAD A LEFTHAND DAY,, THE FOLKS THERE INVITED ALL PERSONS LIVING IN LEFTHAND ,WV , TO COME TO THE GAME, THEY DISPATCHED BUS`S  TO LEFTHAND AND  TOOK THE  THEM TO RICHMOND  FOR THE GAME, THEY TOOK CARE OF ONE NIGHTS LODGING AND FOOD,,  AND RETURN TRIP TO HOME,, THERE WAS TWO FORMER BALL PLAYERS FROM  PITT.PIRATES AND BALTIMORE ORIOLES  THAT MAKE THEIR HOME IN LEFTHAND WV.......IT WAS GREAT TRIP FOR THE FOLKS OF LEFTHAND,,,,,,W.VA..

oliverice
oliverice

I have always thought that left handed people should be taught to write backwards.  Right handed people write "normally" from left to right.  Left handed people would be better served to write from right to left-backwards.  I would just seem a more natural way to write the language as it was created

mrbomb13
mrbomb13

This article is terribly fraught with speculation, shakey correlations, and conclusions that ellicit a, "that's a major stretch"-type response from the average reader.

Clearly, the intent of the author was to pen a puff piece on lefties just to fill space on an article about "Left-handers' Day."  TIME used to have higher standards what's on display here. 

DKO87
DKO87

What about the truly ambidextrous? My son is 4 years old and confused me for years. I could never figure out if he was right or left handed.

Now that he can understand what I am asking, I've tried to get him to tell me, but having a primary hand makes no sense to him. He will just use the closest hand to whatever he wants to do, and in his own words,"switches when one hand gets tired." He even draws with both hands simultaneously.

I'm actually really jealous, because that seems like a very useful ability, but I can't find any real information about what it could mean for him psychologically.

KyleMarisa
KyleMarisa

"An interesting trial published earlier this year even showed that people who clenched their right fists before memorizing a group of words, thereby activating the left sides of their brains, performed better on recall tests than those who balled their right hands into a fist" - reporting fail.

KyleMarisa
KyleMarisa

And if you aren't ambidextrous you clearly can't write right...how can you report the news right if you are biased? - said the ambidextrous writing major you can call to replace Alice Park

bojimbo26
bojimbo26

Slow day in the office ? ( As we in the UK call a non-article ) .

deleonarana
deleonarana

This a classic example of a very inaccurate article.  Of course it´s not for a Peer-Review Journal,  but at least the author should have informed herserf better.  Many of the stuff written here are not true, even when the author writes about Geschwind, and the cause for being left handed, She does quit bad.  But the worst  is She mentions associations (very risky doing so) with autism, dyslexia.   Very very bad article, the author should have consulted first with a physician.

HamidAshouri
HamidAshouri

I use to be right-handed but due to traumatic head injury in the left side of my brain I have muscle atrophy in right side of my body. So,  I cannot write with my right hand as good as I use to. I've got to use  my left hand ever since. Fortunately, it's going well to use my left hand.

Homa
Homa

I have twins, who are said to be Mirror Imaged. One of them is a left-handed. So a higher Testosterone in the womb does not have a role in being a lefty !!! 


ReneeArtigues
ReneeArtigues

I had to stop reading after the assertion that humans are the only species that show handedness. Not at all true. Just like humans show a species-wide trend towards right handedness, orangutans show a species-wide trend towards left handedness. There is no trend in bonobos, while there are right handed species trends in gorillas and chimpanzees.

Do your research before you write an article.

ublooney2
ublooney2

Hey, I've never felt elbowed out.  Have always enjoyed being a "left-hander."  That subtitle must be a reflection of someone's own negative experience.  

DarwinAkbar
DarwinAkbar

"but are at a loss to explain why humans are the only species with handedness."

I am fairly certain this is not true! In fact, studies have shown that animals of higher intelligence exhibit all the traits that people are known for, including handedness, expression of emotion, homosexuality, etc.

Meanwhile, flatfish are a highly asymmetric species that spend their entire life lying on one side, to the extent that their eye and mouth will migrate to one side. I have seen shellfish whose shell spirals in both right-handed and left-handed orientations.

Rockmedia
Rockmedia

Eat and write left handed, but do everything else, with my right hand...or foot.  Not sure what category this lands me.  But I do like celebrations, so yay, me.  :)


D_Coder
D_Coder

@olivericeBut they do... in Hebrew and Arabic.

.cibarA dna werbeH ni ...od yeht tuB

Vancoin
Vancoin

@oliverice In a sense, that's what most left-handers already do by placing the hand above the line being written on and curling the wrist down to avoid dragging the hand over what has just been written.

KyleMarisa
KyleMarisa

Per my comment above, can you get me a visa to the UK? I even named my puppy Winston Churchill.

SmailBuzzby
SmailBuzzby

@NminaAngelica - Your mom gives 31jobs per hour and only earns $78 for it?  Wow, your mom should probably retire before she gets an STD.

Vancoin
Vancoin

@ublooney2 I'm old enough to remember when being left-handed had some real disadvantages. When I was in grade school, it was common practice for teachers to take the pencil from the left hand, whack the offender on the wrist with a ruler and insist that writing be done with the right hand. I spent a lot of time in detention for refusing to do that. There was very little left-handed sporting equipment, or equipment of any kind for that matter, and what was available was custom made and usually very expensive. In the military, it didn't matter how good a shot you might be left-handed, you were forced to shoot right-handed. That policy didn't change until the '60s. Things are a lot better now than they used to be.

MikeCairns1
MikeCairns1

@Rockmedia  left handed ppl are usually better boxers and street fighters,also am a lefter so is quite few of my family and am diyslexic lol.i wouldnt change my hand from left 2 right left handed ppl are veryy neat writers to.i love been left handed i feel special cause we are but a few compaired to right handers,its good to be diffreent than the usual and more right handers,4 play is more rewarding 4 women of a left handedlover..


Sapphire19a
Sapphire19a

@Vancoin @oliverice  

I watch other left-handers write like this and wonder just how they do it !  I much prefer to 'tilt' my writing paper at an angle - and write with the hand in a normal position.  This assumes you are not writing with a fountain pen however, when either way is an absolute nightmare !!