December 6, 2011

Facts on Left-Handers

Lefthanded people are interesting, in part because they don't make up a strong identity politics group and thus don't benefit from legal protection. There is no Lefthanders History Month of PBS documentaries on Lefthander Pride. This is despite a stringent period of anti-lefthanded bias in the early 20th Century. Ronald Reagan, for instance, was a natural lefthander converted to writing righthanded accordign to the advanced thinking of his time. At some point, before WWII, I believe, there was something of a Lefthander's Liberation movement that reversed this pattern of oppressing natural lefties to switch, but unlike other such movements, this one has almost completely disappeared from media memory. 

Here are some facts from the WSJ on lefties:
About 10% of people are left-handed, according to expert estimates. Another 1% of the population is mixed-handed. What causes people not to favor their right hand is only partly due to genetics—even identical twins, who have 100% of the same genes, don't always share handedness.
... More important, researchers say, are environmental factors—especially stress—in the womb. Babies born to older mothers or at a lower birth weight are more likely to be lefties, for example. And mothers who were exposed to unusually high levels of stress during pregnancy are more likely to give birth to a left-handed child. A review of research, published in 2009 in the journal Neuropsychologia, estimated that about 25% of the variability in handedness is due to genetics.

Handedness is a form of human biodiversity that is only moderately heritable, which explains much about about their lack of political power as a group. Identity groups are largely constructed from relations of blood and marriage, language (e.g., signing deaf people are a strong identity group despite their problems because they have Deaf Culture, while deaf people who don't sign aren't really politically deaf), sexual relations (homosexuals), and sex.
On average there is no difference in intelligence between right-and left-handed people. But lefties do better on an element of creativity known as divergent thinking.

Six of the last 12 U.S. presidents, including Barack Obama and George H. W. Bush, have been lefties. 
Left-handed people earn on average 10% lower salaries than righties, according to a recent study. Findings of some earlier studies on income have been mixed. 
Despite popular misperceptions, lefties aren't more accident prone than right-handed people and don't tend to die at a younger age. 
Left-handedness has been linked to increased risk of certain neurodevelopmental disorders like schizophrenia and ADHD. Mixed-handedness is even more strongly associated with ADHD. 
Most people's brains have a dominant side. More symmetrical brains of mixed-handed people may explain the link to some neural disorders.

While lefties make up about 10% of the overall population, about 20% of people with schizophrenia are lefties, for example. Links between left-handedness and dyslexia, ADHD and some mood disorders have also been reported in research studies.

Recall, the standard thing nice white people always say about race -- "He just happens to be black." As George Carlin pointed out, if somebody has two black parents, "Where does the surprise part come in? I would think it would be more unusual if he just "happened to be" Scandinavian!"

But, it's much truer to say "He just happens to be lefthanded." But, because it's true, hardly anybody ever says it.

42 comments:

DCThrowback said...

My guess is that Ned's dad contributed to his mom's stressful pregnancy.

Clicky here Neighborino!

Anonymous said...

I use a left handed mouse because i got carpal tunnel in the early days of computerin' ... i am actually far more comfortable with the left handed mouse... i think it was easy because i did not learn to have a right handed mouse.

Steve Sailer said...

What's right handed and what's left handed can be pretty arbitrary. For example, more than a few great golfers were lefthanders playing with right handed clubs (Ben Hogan) because they started out borrowing somebody else's righthanded clubs. But Phil Mickelson is a natural righthander who plays with lefthanded kids because when he was 18 months old, he wanted to swing along with his dad in the backyard, so his dad put him right in front of him facing him and had him swing a lefthanded baby club.

Throwing overhand, however, is a difficult thing to do against nature. An Olympic pistol shooter lost his right hand during WWII and came back and gold-medaled shooting left handed. But I've never heard of a major league pitcher switching throwing arms when he wears out one arm.

agnostic said...

If I remember correctly, lefties were over-represented among diagnosed pedophiles. Wrote that up for GNXP a few years ago.

The authors thought that both pedophilia and left-handedness was due to a disturbance during pregnancy, possibly an infection.

Ian said...

Six of the last 12 U.S. presidents, including Barack Obama and George H. W. Bush, have been lefties.

Indeed.

Anonymous said...

Here's your ambidextrous pitcher:

http://www.youtube.com/watch?v=8U2xkHOTvvw

TGGP said...

Back in the day in Catholic schools the nuns would reportedly smack your hand with a ruler if you wrote with the left. Because they took latin back then, and left = sinister.

Anonymous said...

"Six of the last 12 U.S. presidents, including Barack Obama and George H. W. Bush, have been lefties."

Well, let's put a stop to that. No more lefty Prezes. They range from competent but perverted, Clinton, to downright incompetent.

tommy said...

What's right handed and what's left handed can be pretty arbitrary.

I'm ambidextrous. I can write with both hands, but I usually use my right and I prefer to hold forks and spoons with my right. I was forced to choose my right hand in elementary school by a teacher who didn't like me changing hands while practicing penmanship. I'm a left-handed rifleman, but a right-handed pistol shot. I shoot a basketball as a lefty. It all seems to center around forward projection, but it is difficult to pin down exactly what triggers a preference for right or left.

Incidentally, one of my brothers is a lefty and the other is right-handed. Two of my cousins by my mother's sister are lefties and one is a righty. (One of the lefties suffers from dyslexia.) Both my mother's brothers are right-handed and their very artistic half-brother is a lefty. Both my mother and her sister are right-handed, but both can write more legibly with their left than can your average person. Everyone on my father's side is a righty.

What is mysterious to me is why left-handedness is even moderately heritable. Given the difficulties, what possible advantage could it have given early man to be left-handed or ambidextrous?

tommy said...

The authors thought that both pedophilia and left-handedness was due to a disturbance during pregnancy, possibly an infection.

There are neuroscientists who have speculated that schizophrenia is caused by an infection during pregnancy or early childhood. A genetic predisposition + early cytomegalovirus infection has been named as one suspect, but given the prevalence of CMV infection among the general population it might be difficult to prove. It would be interesting to know if CMV infection or increased CMV activity has any relationship to left-handedness or pedophilia.

Jehu said...

Tommy,
Left-handed people like myself compete against or fight against right handers FAR more frequently than the converse. So the advantage of being left-handed (as long as left-handers are rare) is that the competition has far less experience coping with you than vice-versa. This applies at least in pitching and fencing.

Hereward said...

I write left handed, fence left handed, and shoot rifle and bow right handed. When shooting pistol one-handed, I can use either hand but prefer the left. When using a two-handed grip, I hold the handgun in my right hand and wrap my left hand around my right. I throw knife and tomahawk left handed, but when I played baseball or softball when I was a kid, I threw right handed.

Polymath said...

My parents are both clear left-handers, and my sister and I are both righties, so it's not purely a recessive gene trait as the books said when I was a kid. But I may be naturally a little ambidextrous; although I write and throw balls righty, I naturally move chess pieces and throw frisbees lefty. Throwing overhand is a very difficult skill to learn ambidextrously for some reason, I wonder why.

Lugash. said...

I am Lugash.

I write left handed, fence left handed, and shoot rifle and bow right handed. When shooting pistol one-handed, I can use either hand but prefer the left. When using a two-handed grip, I hold the handgun in my right hand and wrap my left hand around my right. I throw knife and tomahawk left handed, but when I played baseball or softball when I was a kid, I threw right handed.

Who are you, some sort of weird mix of Wild Bill Hickock, a Three Musketeer and Indian? ;)

Your handgun shooting is really interesting. Do you use the same dominant eye when shooting single versus two handed?

On average there is no difference in intelligence between right-and left-handed people. But lefties do better on an element of creativity known as divergent thinking.

On average, maybe. But I've observed more lefties out on the right hand side of the curve(pun intended) and IIRC most studies have shown that as well.

I am Lugash.

Reg Cæsar said...

When I was in boot camp, we could earn pistol and rifle medals. The guys who won only one medal almost always won it in rifle. Not me. My only medal was in pistol.

I shot both tests right-handed. I suspect the difference was that I probably used my left eye to aim the pistol, which would be awkward with the rifle.

I doubt I was left-eye-dominant in those days, as I'm not now. Something else made using the left eye more efficient.

As a right-swinging tween, I decided to try switch-hitting. But I only ever faced a lefty pitcher once (and struck out), so now I can only bat left.

On the other hand (PTP), changing to the Continental practise of holding the fork in the left hand worked wonders. I haven't dropped my silverware in thirty years!

Nadaav said...

Interesting.

I'm an identical mirror twin. I'm left-handed and my brother's right-handed. We were both born underweight and a month early. These days it seems like we're more "mirror" than "twin."

I've always found lateralism fascinating. I forget what species of fish it was, but I read somewhere that they tend to like to turn right, except for a few who prefer to turn left. The evolutionary advantage is that predators have to guess which way most of the school is going to turn. If it was a 50/50 split they'd make out with a good meal every time just by guessing randomly, so there's an advantage to having only a minority be different.

Maybe those higher rates of schizophrenia and other mental disorders are a way of keeping handedness out of balance? I can't remember where but I also read that aboriginal Australians were half lefty, half righty. An island phenomenon?

Not only have 6 of the last dozen presidents been left-handed, but a huge proportion of presidential candidates have been as well. McCain was, and I think Perot was also. Dole was, of course, though he wasn't born that way.

LeBron James signs autographs left-handed but shoots righty.

Hard accurate throwing is an excellent subject in its own rite. My grandfather, an evolutionary psychologist, has spent the last several decades developing a thesis on the origins of this uniquely human act, with the central claim being that it was the big qualifying benefit we got from bipedalism. Could there be a lateralism aspect there too?

Catperson said...

I've read that lefties have more extreme intelligence. Their average IQ might not differ from right handers but their standard deviation is probably larger causing them to be overrepresented both among geniuses and retardates.

Chiral Architect said...

Interesting statistics: because there are more naturally right-handed people, there will be more UNnaturally left-handed people. If (say) 90% of a population are naturally right-handed and 10% naturally left-handed, a brain insult that switches handedness will switch many more right-handers to left-handedness than left-handers to right-handedness. Hence the higher incidence of neurological disorders among left-handers. So, as you'd expect, there are more left-handed males than females.

jody said...

my brother is left handed, so i am always looking at this issue. he was also born prematurely, and has a learning disability, so that corroborates the research in the article.

"Despite popular misperceptions, lefties aren't more accident prone than right-handed people"

i'm not sure about this. they may not die at a younger age but i believe the injury rate for left handed blue collar laborers is definitely higher. most power tools and construction equipment is set up for right handed use. this has been changing somewhat over time, as there's been a movement towards ambidextrous tools, but things can still get dangerous for lefties out there. i'm not sure if the situation is the same in the food industry, but butchering animals in a slaughterhouse, or even cutting in a deli, may present similar issues.

almost all small arms are set up for right handed men (not people, men. they're absolutely not designed for women) and left handed men have more trouble using them. doesn't mean left handers can't be good shots, plenty are, but the guns often sabotage them and directly contradict their natural instincts. most semi-auto and auto long guns eject either across or even directly into a lefty's body. bolt handles are on the wrong side of a bolt action. lever action and slide action are usually OK though.

if a lefty uses a normal rifle or submachinegun there's no way he won't occassionally get hurt by his own weapon - anybody can, but we're talking about getting hurt during normal use in a way a righty almost never would. using a bullpup left handed would probably suck the most. they do make left handed versions of some guns, and some guns are designed as ambi from scratch with no handedness.

handguns, which are even more "handed" than long guns, can become a lot of trouble. magazine ejects are in the wrong place, revolver cylinders open into empty space, safety buttons can't be reached, and so forth. leftys overcome this with lots of practice but they can still get tripped up needlessly and handgun malfunctions are more likely to get you injured than long gun screw ups. concealed carry is at an all-time high, so left handed people carrying handguns set up for right handed people is more common than ever.

jody said...

i'm weakly ambidextrous naturally, and have become functionally ambi on some tasks, by forcing it to happen with practice. i can write with both hands, and throw OK left handed - not that great, but better than somebody who is not ambi at all. you can see how highly specific that genetic throwing behavior is in males (females don't have it, as i've mentioned before) by taking the baseball or football or basketball out of their strong hand and putting it in their weak hand and having them throw. they basically start to throw like a girl.

from my sports research, being left handed is an advantage in tennis and boxing. it doesn't seem to be a disadvantage in any sport, except arm wrestling, which is such a small sport. i think travis bagent, one of the best american arm wrestlers ever, is left handed. he's forced to go right handed in all tournaments though. so it's impressive he can put down almost everybody with his weak arm.

left handed guitar players may be better, i'm not sure about this, i need to research this more.

then you get into things like, eye dominance versus hand dominance, which is a factor in baseball, ice hockey, as well as shooting weapons.

there's even foot dominance, with not all right handed people also being "right footed" and vice versa.

Anonymous said...

I do thing lefties are overrepresented among high IQ people. When I was at college (one of the HYP Ivies) I remember in freshman economics the professor asked the large class how many were left handed so they could assess the kind of desks they needed, and a very large percentage raised their hands.

I think mixed is more common than pure lefthandedness. I write with my left hand but throw with my right and my right eye is the dominant one. My father and paternal half-brother are also part-left handed.

Anonymous said...

Elitist writes:
I'm a lefty (like my father), but throw & catch with my right, etc.
I'm also gay, & artistically & musically gifted. I managed to earn a PhD at an Ivy, but very belatedly, by the skin of my teeth, after a lot of conflict :
my professors classified me as brilliant and gifted but also combative, hypercritical, uncooperative, etc. etc.
in other words, my thinking (among other things) is decidedly deviant, meaning:
present me with an argument, and I will pick it apart, reverse it, turn it upside down. This makes it possible for me to devise arguments which are novel and which enrage people.
I am one of those people psychiatrists like to medicate for “social disorder,” meaning I hate sitting around for hours listening to idiot pseudo-intellectual, academic posers exchange pretentious blather, and the thought of attending a professional conference in my field - or even sitting through one excruciatingly boring lecture by a colleague - makes me violently physically ill.
This has meant abandoning an academic career while watching people who are miles below me intellectually succeed.
Aside from being argumentative & critical, what has really made it impossible for me to fit into any institution is the fact that I like to change my mind - and to learn new things.
I'm interested in everything, and have never really made up my mind which to focus on.
I would be extraordinarily interested in knowing whether left-handed people are more likely to revise their opinions, to switch fields, to make erratic swerves in their intellectual development, etc..
abandoning the egalitarian mythology for race realism seemed completely natural to me:
I examined the issue from all sides, processed a range of views, and decided the Darwin was right.
My so-called intellectual friends were just as shocked as they would have been had announced my membership in the Nazi party.

I have never gotten over my unease over the valleys of realizing, when I was around 15, that most successful intellectuals and academics are in fact quite stupid, puppets who parrot phrases and slogans other people invented.

I once participated in a study which sought to correlate lefthandedness with homosexuality, artistic gifts, high IQ, trauma during pregnancy, autoimmune disorders, difficulties with social adjustment, and several other traits.
I distinctly remember checking every single box on the form.

sideways said...

There's been at least one time in pro-ball where an ambidextrous pitcher went up against a switch hitter, leading to comedy. http://sports.espn.go.com/mlb/news/story?id=3455201

I'm ambidextrous and for some reason can only throw a good spiral with my left hand.

Anonymous said...

Greg Harris pitched with both arms at the end of his career with the old Montreal Expos.

Anonymous said...

i'm left-handed and so is my father, however he writes with his right hand. he was a child in india in the 50s and his father beat the left-handedness out of him

Jacob Roberson said...

Friend of mine is lefty, and her husband. And then their daughter married a guy, and both his parents are left-handed. The bride, the groom, and all of their siblings (big families on both sides) are right-handed.

Take that, you "Genetics Matters" crazies. ;)

Anonymous said...

Because they took latin back then, and left = sinister.

No, it's far more widespread than Latin speakers. Japanese people to this day will not let students learn to write left-handed. Or at least, they didn't when I was there ten years ago.

The bad "sinister/gauche" connotations came out of this bias against lefties, not the other way round.

kgks said...

I find that my left hand works surprisingly well at taking over some task of secondary importance and started after I'm busy doing something with my right hand. Take driving, for instance: I find I will always keep my right hand on the steering wheel when flipping someone off for their no doubt left-handed infractions of the rules of the road. Honking seems to be a more dominant, assertive act, however, as I tend to use my right hand for this form of consequence for aberrant drivers.

Hereward said...

Lugash,
Who are you, some sort of weird mix of Wild Bill Hickock, a Three Musketeer and Indian? ;)
I try to be! I'm involved in "buckskinning" (frontier reenacting) which involves competition with muzzleloading firearms as well as thrown knife and tomahawk. I took fencing as a child, and am currently involved in "Western Martial Arts" - historical combat arts like pugilism, 19-century cane, Spanish knife, etc.
I'm right-eye dominant in all my shooting.

Geoff Matthews said...

My oldest and my 3rd child are both left handed. My wife has two brothers that are left-handed, and I have a brother who is left-handed.
My sons are, of course, brilliant.

Anonymous said...

Being naturally lefthanded, I simply think what is logical then do the opposite and am then in perfect accord with the righthanded world. Truly.
That said, (because of how I was taught and the glove I was given) I play tennis righthanded, badminton equally well either handed but baseball righthanded only. When I broke my left arm as a child I learned to make do quite well with my right hand but quickly reverted once the cast came off.

samroot said...

I am left handed, and my twin sister is right handed. I have fraternal twin older brothers, where one is left handed, and the other is right handed. I always thought these were uniquely freakish occurrences, until I read an article on this in the NY Times. It said, because of the positioning in the womb, only the opposite, outside hand, in each twin was free to move,suck, and therefore dominate.
AS a youth, I began to switch hit, and then bat right so much, I couldn't bat left anymore.

Kevin Joyce said...

There is a historical reason for right-hand penmanship that is often forgotten today. Dip pens were used in schools until quite recently. A left-hand writer would find it difficult to avoid smudging the ink, since the writing hand would follow the nib. Now that writing is done with a ball-point, this is not a concern.

alonzo portfolio said...

... the competition has far less experience coping with you than vice-versa. This applies ..

heavily in basketball. Defenders often just can't get used to someone driving to the left.

Anonymous said...

Kevin,
Definitely not true, pencils ball point pens, everything smudged and got on the side of my hand. I finally learned to pick up my hand wich leads to a very unstable writing position.

Anonymous said...

I have three founding partners at my law firm, all three T-6 law school grads. Each has a completely different personality, all three are genius lawyers, and all three are lefties. What are the chances?

candid observer said...

So what I really want to know about an ambidextrous pitcher is this:

Can they pitch two games in the rotation?

Crawfurdmuir said...

@Hereward, Lugash, Reg Cæsar - I write with the left hand, and shoot right-handed - mostly shotgun, but also rifle and pistol. Shotgun shooting is particularly dependent on eye-hand coordination, and I attribute my preference for right-handed shooting to my strong right-eye dominance. It seems quite unnatural and difficult for me to shoot from the left shoulder for this reason.

Right-handed tools - scissors, saws, etc. - have never posed any problem for me. Dining is an interesting issue. The standard American table manners call for one to hold the fork with the left hand, use the knife with the right, then to set the knife down and transfer the fork to the right hand. Europeans don't do this. I could never manage the fork-transfering business, and my mother never insisted that I do. No one has ever asked me if my table manners are the result of left-handedness, but a number of people have remarked to me that I dine in the European fashion.

@Kevin Joyce, I have always preferred a fountain pen and have never smeared the ink. I note that many left-handers have a very peculiar way of holding a pen, and it is simply a question of learning not to do this. Part of it is how you orient the paper; if a left-hander orients the paper as a right-hander would, he is writing "uphill," which is difficult to do. The answer is to turn the paper. Also, an oblique nib is very helpful in producing pleasing handwriting with the left hand. Pelikan makes suitable nibs. Most stationers do not carry them, but can order them on request.

left while writing said...

"There is a historical reason for right-hand penmanship that is often forgotten today. Dip pens were used in schools until quite recently. A left-hand writer would find it difficult to avoid smudging the ink, since the writing hand would follow the nib. Now that writing is done with a ball-point, this is not a concern."

I don't remember dip-pens (though the schools still had desks with those holes in the upper right corner for holding ink wells.) However, even cartridge fountain pens, smearing the ink was a problem for lefties. In fact, even ballpoint and pencil marks will smear if your hand is sitting on them right after they are put on the paper. Not as bad as the fountain pen ink, but still discernable. I always had ink and pencil smears on the edge of my left hand.
There were practical reasons for making kids use the right hand, but I'm glad they weren't doing it any more by time I was in school. They haven't done that for eons. My much older brother, who started school in 1954, was not forced to write with his right hand.

Anonymous said...

Are there stats on left handedness by race? I suspect there are far more European left handers than Asian, for example.

Anonymous said...

You forgot that left handers are more creative such as Bill Gates III versus Steve Jobs you insensitive clod!

Anonymous said...

I became fascinated with lefties a few years ago when I realized the overwhelming majority of my closest friends in my 29 years of life were lefties. My Mother (like her Father and all 3 of her siblings) is a very dominant lefty and I myself do some things left handed. So i've wondered if there is a genetic component to it. Lefties do seem either really the smart or creative type or the weird, ding-bat type. One of my lefty friends swears that Phil Mickelson's playing golf left handed is the main reason for his fuck ups and melt downs.