Biology Thursday, July 22, 2004 . This is a SciScoop post by apsmith
The study was done by Peter Hepper of the Fetal Behaviour Research Centre at Queen’s University, Belfast, using ultrasound scans of 1000 fetuses. 9 out of 10 fetuses at 15 weeks preferred sucking their right thumbs. Followups for 75 of them 10 to 12 years later found all 60 of the right-hand thumb suckers were indeed right-handed, and 10 of the 15 left thumb suckers were left-handed.
Even before they start sucking thumbs, the fetuses wave their arms about. This is long before there is any neural connection between arm and brain, and yet even then, at 10 weeks or so, there was a similar strong preference for right-arm waving.
It had been previously supposed that the handedness preference derives from left-brain right-brain differentiation – this study suggests that in fact the reverse happens: almost from the start one side of the body is preferred over the other, and the greater muscular activity likely leads, through the early sensory connections, to differences between the associated sides of the brain as that develops.
So why do lefties get such a bad rap? And why do they seem to be disproportionately successful in politics and creative activities? At least we now know the rumors about premature death are not true!
Previously: « Star of diary
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12 Responses to Born Sinister
mtigges
July 23rd, 2004 at 8:31 am
With the hot weather these days, I’ve taken to leaving my socks in my cycling shoes and wearing sandels through the day. When I put the shoes back on, I always seem to take the sock out of the left shoe first, and put it on my right foot. I’m always left standing there with my right sock clad foot hanging in the air, with no empty shoe to put it in. I’ve noticed this so often, that I have to bend down and grab the left sock out of the right shoe with my right foot in the air, that it’s really struck me. It’s quite strange. I have a predilection to putting on the right sock first. (I’m right-handed.) But for some reason I never take the sock out of the right shoe first.
gypsysoul
July 23rd, 2004 at 10:04 am
since I’m not only left-handed, I was born on Julius Caesar’s birthday :)…
The next-to-last paragraph is unnerving in that it might provide fuel for the ongoing argument on ss and elsewhere that our behavior dictates our brain chemistry, rather than, at least in part, the other way around.
I am leaving for the beach for a week– hope I can find a computer somewhere to keep POSTED!
BigZaphod
July 23rd, 2004 at 11:57 am
I’ve always been right handed, but I can write reasonably well with my left. But its slow and takes time. :-)
The curious thing is that I play hockey using a left-handed stick. Partly, I think, because it happened to be available when I first started playing. But I’m not sure. I’ve tried right-handed and I suck much more than normal that way. And yet, for pretty much everything else, I seem to work much better on the right. My dad is left handed, though, so maybe there’s some kind of residual left-ness in me. :-)
mtigges
July 23rd, 2004 at 1:45 pm
Same for me, I play both hockey and baseball (at bats) left-handed, though I am otherwise right handed, I play golf right, and find a left-handed golf swing to be the height of strange feelings. But, being German I can eat both ways (for those who don’t know Europeans generally eat with their forks opposite to us). Maybe I should be less general, the Germans I know all do.
Anonymous
July 23rd, 2004 at 10:11 pm
Not to freak you out or anything, but strong hand preference in a child under 2 is sometimes a sign of something wrong developmentally. Maybe (probably) nothing, but something you might consider getting checked out.
My daughter is “developmentally delayed”, and the question of hand preference came up a number of times early in her treatment. While it wasn’t the case with her, my brother-in-law’s nephew is in therapy for a condition which was diagnosed because of his strong preference for his right hand at 16 months or so (I don’t know more details).
Anonymous
July 23rd, 2004 at 10:13 pm
It’s late, okay?
apsmith
July 24th, 2004 at 12:20 pm
I think in this case it’s ok. I can certainly see if a child was not using one side at all, or displaying pain or clear reluctance or something, that might be a medical condition. But in this case it’s just us parents observing the strength with which he throws things, the frequency with which he picks things up, in one hand vs. the other. He’s quite happy using his left hand for things – he’ll happily hold a cookie or ball in each – but he just uses the right more. He certainly looks very healthy to me :-)
Drog
July 25th, 2004 at 10:18 pm
Neat. I am exactly the same–right-handed, play golf right-handed, play hockey and baseball left-handed. And I eat with both European and North American styles.
jxliv7
July 26th, 2004 at 12:19 am
.
…I’ve always been a little clumsy with the left hand. At least — as I’ve read somewhere — if I should loose the use of my right hand I will adapt and my left-handed coordination will improve considerably. I think the body is like that with eyes, hearing, sight, etc.
There are somethings that I do ambidextrous: bat at baseball, eat, reach out for and handle objects. But not write.
I’m not sure when children are supposed to start favoring a left or right hand, but my son started early (less than 2) using his right hand. The tragedy with children is when a parent forces the child to use one hand or another, although I think it happens less these days.
jon
mtigges
July 26th, 2004 at 9:18 am
… we’re both Canadian, coincidence?
kryptothesuperdog
July 26th, 2004 at 9:52 am
I’m right-handed in terms of writing, but I eat the left-handed way and I’ve always worn my watch on my right hand too. I’m just odd, really :-)
Not strictly related, but I’m interested. Do right-handed US drivers have trouble adapting to driving in the UK? Over here we’re used to having to use our left hands on the gear stick, so moving to the opposite in the US isn’t a problem. But coming in the other direction sounds like it’d be pretty tricky…
teece
July 27th, 2004 at 12:27 am
I’m the mirror of you folks. I was born left-handed. Any skill I learned early, I learned to do with my left hand. Thus I write, eat, brush my teeth, etc. with my left hand.
Things I learned later in life I do with either hand: throwing a ball, darts, right. I use a mouse with my right hand (though that’s mainly because most mice are right-handed).
Actually, in adulthood, any new task I have a choice of learning which hand to learn to use. I can actually throw darts equally well with my left hand, but it just feels weird.
But I learned to belay (rock-climbing) left-handed, and wouldn’t dream of switching. But I bat right-handed. When I once picked up a friend’s guitar, he said I was holding it backwards (eg, left-handed). I’d be curious to drive a car in the UK and see if shifting with my left hand felt weird.
So I guess I ambidextrous. But I think of myself as left-handed. The Left Hander Syndrome is actually an interesting book all about this topic (by a damn righty!). Most lefties have no choice but to be somewhat ambidextrous, as it is a right handed world. Try and use the circular saw with your left hand, and you’re liable to loose some limbs.