Left Handedness Nature or Nurture ?

My father was left. My mother was right.

My two brothers and I are left, and my 5 sisters are right.

Are there any studies that have explored this phenomenon ?

I wonder if the trait is sex chromosone related or if it is learned behavior due to immitation at the moment the child first recognizes a parent using one hand dominantly to complete a task.

I also welcome anecdotal information.

I doubt it’s learned behavior My parents were right handed but I’m a southpaw. Wouldn’t I have learned to be right handed if that theory were true?

In the mid-60’s the school tried to “cure” me of my left handedness. Writing and cutting with a scissors did not work well using my right hand. Because of the fuss my old man made they finally stoped trying to make me and others righties, and the jerks were forced to provide left handed scissors in art class. Unbelievable that as recenty as 1965 authorities thought left handedness was something to be “cured”.:mad:

Sorry, I have no cite, but when I was a child, public schools had recently banned the practice of discourging left-handedness. There was “evidence” that it could cause stuttering.
I did find this, but I have no idea as to its veracity

I am a lefty as was my son. (I’m female)

Maternal Grandmother-Left handed (forced to switch to right hand)
Mother-Right handed
Sister #1-Left handed
Sister #2-Right handed
Brother-Right handed
Me (female)-Left handed
My son #1-Left handed
My son #2-Right handed

I would say nature- I watched my 2 boys very carefully and they both displayed their preferred “handedness” before one year of age. Even if you offered a toy to the non-dominant hand, each would reach across with the dominant hand to grab the toy.

I did startle my mother after I had done some surgery rotations. I was doing some sewing and she walked by and stopped and commented “You are sewing right handed!”. “Yeah, it really helps in the operating room to be able to switch from left to right at times, and most instruments are designed for right handed use.”

Mostly nature, but it can be changed fairly easily, especially if you start young enough. One noted example is Phil Mickelson, famously referred to as “Lefty”. He’s actually right handed, but learned to play golf left handed by watching his father (I think it was his father) and imitating him. Standing face-to-face, he’d swing as a lefty.

And it’s not just humans. Handedness is seen in chimps, and I believe some other non-human animals as well.

As far as I can remember, everyone in my family is right handed except my maternal grandfather and my second-youngest brother. When my brother was in grade school the nuns tried to make him write with his right hand, until my mother insisted that he be allowed to use his left hand.

My youngest brother, however, shoots pool left-handed because Grandpa was the one who taught him to play. And when I played table tennis in college I used to occasionally switch hands in mid game, just to mess with my opponents.

I think it’s nature. My brother and one daughter are lefties, other daughter and I are right-handed, as is the girls’ dad.

I’m left-handed as is my brother. Our parents are right-handed. My husband and son are righties, but my daughter is a leftie.

My mom once told my young daughter that “left-handed people were not of God”. If my brother and I are the spawn of Satan, what’s that make her?

My uncle could write with either hand backwards or frontwards. Amazing, but I am sure that he practiced a lot when he was young.

I find it nature, because oddly enough I write right handed, but everything else, baseball to golf, bowling is left hand. I can’t get used to doing things with my right hand except for writing, which feels natural for writing but nothing else. And I never was forced to write with my right hand.

I would say your statement is a case for nurture. I too swing like a rightie which is why I’ve always had a lousy slapshot. I expect that might be because I never learned hockey or batting from my dad.

Totally anecdotal but,

I was ambidexterous until I was 6, at which point my first grade teacher suggested that I pick which hand I wanted to “really” learn to write with (my kindergarden teacher let me switch from hand to hand I guess). I am now so strongly right handed that my left hand isn’t good for anything except typing and playing guitar.

My experience makes me think that even if the is a genetic componant to it at a young age, nurture is still a big factor.

Both parents are righties.

All three of us are lefties. However, we suspect that the youngest switched himself to lefty to be like his big sibs based on old home movies. So make of that what you will. :smiley:

That said, though, I can very easily switch the hand that I lead with when signing if my other hand’s occupied doing something. (In ASL and other sign languages, you’ll have a ‘dominant’ hand and a ‘subordinate’ hand) That’s about the only ‘switching’ I can do – most everything else is left handed for me except mousing.

My grandfather, father, I and my son are left-handed. Our siblings are all right-handed. It has to be “nature” because certainly none of us were forced to use our left hands.

The school forced my father to write with his right hand and he did, indeed, develop a stutter. When my school asked if I should be taught to write with my right-hand, it was my right-handed mother who pitched a bitch and told them to leave me alone.

Mousing ! Does any lefty mouse left handed ? I’ve tried and its a disaster . Never had any problem learning “right” the first time when the mouse was always placed on the right.

Your natural tendency to pick one hand or the other for a dominant hand is determined genetically (this is the answer to almost every nature v nurture question). Here’s an example recent article:

http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=12596796

We’ll eventually get rid of questions that wonder if a particular trait has a mostly genetic underpinning; some will just take longer than others to identify the genes involved.

Anyway, the genetic influence here tends to make you right or left-brained (in simple terms), and of course since most of us have dominant left hemispheres for motor control, about 90% of us are right-handed.

Now that doesn’t mean, as has been pointed out, that you can’t train the other side to perform well–even equally well–for a given motor function. And of course if you lose part of your motor cortex early enough in life, the brain can do amazing things taking over for the lost part. So there is a substantial opportunity for nurture to make what would otherwise be the clumsier side more facile.

There are other ways besides handedness to decide which is your dominant hemisphere (this is in itself a simplistic concept). You can point to something and see which eye was dominant, for instance, by closing each eye one at a time. Or make a circle with your index finger and thumb, hold out a hand and enclose a distant object, and see which eye is being used. Once you realize what you are doing, though, these tricks become conscious awareness and don’t work as well.

And as pointed out re Phil Mickelson, or with computer mousing, it can be simply how you were nurtured if it’s a particular motor behaviour. I shoot a gun righty, a bow and arrow left, write right-handed and have a left dominant eye. The Pedant is a barely functioning kludge, alas. Damn genes.

I’m opposite. Shoot left with a right dominant eye. That really sucks when you’re trying to line up a sight on the barrel of a rifle.

I’m inclined to say “nurture” in the sense that it may be due to how the fetal brain develops, stemming from whatever random conditions exist in the uterus at the time.
Longtime lefty, mousing right because all the work/school computers are set up that way and it’s easier to adapt than resist.

I don’t buy that.

Lets not forget many pairs of identical twins have one twin right handed and one left handed.
Also, the incidence of left handedness increases when left handedness of parents increases. That is, if neither parent is left handed, the percentage is roughly 10%, if one, 15%, if both parents are left handed then the percentage jumps to 20%. There is definitely a genetic link but the twin statistics indicated that some chemical signals affect development in the womb.
There are many interesting theories regarding left handedness. I’m surprised that none of them have been offered so far.