Anne Chivas

When I was about five years old I showed a preference for the left hand and my teacher was determined that I was going to learn to write with my right hand to the extent that she used to sneak up on me with a big stick and belt the pencil out of my hand and then she would rip the page out of the book and throw the book across the room.

Narration

Despite the pressure to conform around 10% of us describe ourselves as left-handed, based mainly on the hand we write with. In reality left-handers often rely on their right hand for many tasks. Right handers rarely use anything else. It’s the same in every culture. The vast majority of people are right-handed. Why should that be? Is there anything wrong with being left? If there is, evolution should have killed off the lefties long ago?

Prof MICHAEL CORBALLIS, University of Auckland

You would think we might be better off to be ambidextrous, having the ability to do things equally with the two hands. But not so. So something in evolution has created this assymetry. And it’s done in a mysterious way.

Prof CHRIS McMANUS, University College London

There must be some advantage in being left handed but at the moment we don't know what that is but there's also a strong advantage in evolutionary terms in being right handed. That's what the vast majority of us are.

Narration

The right must rule for a reason. One of the earliest explanations came from armed combat. Nineteenth century man of letters Thomas Carlyle suggested that left-handed swordsmen were more likely to die in battle. It wasn’t because of their swordplay but because of the position of the shield. It effectively exposes the heart. More right-handers lived to fight again. Nice story, but many more plausible theories have come along since.

For one cultural pressure. According to neuropsychologist, Ken Provins, we’re all free to choose which hand we use, but we’ve constructed a world which coerces us to use the right.

Prof KEN PROVINS, University of Queensland

Now most people wouldn’t think a camera was biased but in fact they’re all made for operation with the right index finger and you put it up to your eye...Well, here we’ve a water jug. If you pick it up with your right hand you can see how much water you’ve got - no difficulty. Pick it up with your left hand and you can see nothing!.... Every other jug is the same.

Narration

Everywhere you look, the designs push left-handers to the right. The bias is at the core of our deepest beliefs.

Prof KEN PROVINS, University of Queensland

What does seem to be evident is a universal belief...associating things that are on the right side with righteousness, light, life all things that are are good and desirable..... whereas the left seems to be universally associated with things that are wicked or darkness, damnation, the devil.

MATHEW 25

Then shall the king say unto them on his right hand, come ye blessed of my father, inherit the kingdom prepared for you...
Then shall He say also unto them on the left hand, depart from me ye cursed into everlasting fire. Prepare for the devil and his angels

Narration

There’s no justification for damning the left. Ken says It is just as capable as the right. Take typing for example. Both hands have to learn highly complex movements. In tests they’re equally fast and accurate. The push to right-handedness begins in the cradle. At this age, both hands are struggling for control and they’ll grasp whatever comes within reach.

Prof KEN PROVINS, University of Queensland

And it doesn't take much imagination to realise that if there is this slight bias in the world particularly from parents or teachers or whoever in the nursery that it finds things more often presented to one hand than the other it will tend to develop that sort of habit and that sort of a preference for that hand.

Narration

The 90% of us who are right-handed can inadvertently persuade our children to follow suit . Innocent explorations with a paintbrush can decide which hand will grasp the pen. Writing is such a complex skill that it takes years to teach just one hand. All that practice creates a well-worn mental pathway. So it feels natural to use the writing hand for other manual tasks. According to Ken Provins what we do with our hands wires our brain. But there’s a problem in attributing handedness solely to environmental influences. It doesn’t explain why the preference for the right in the first place....

As early as 1861 a French surgeon, Paul Broca, had an explanation. He announced that it’s the result of the brain having a dominant left hemisphere. In other words the brain wires the hand in a crossed-over kind of way. Broca assumed that the wiring is flipped over in left-handers.

Dr Mike Nicholls, a research psychologist at the University of Melbourne has been trying to find out how these differences in brain dominance come about. It’s led him to test a controversial theory - that handedness can result from events within the womb. All foetuses are exposed to the hormone testosterone. Males get more. It’s what makes them masculine. But Mike thinks that if embryos, either male or female, are exposed to high levels of testosterone it alters the growth of the brain.

DR MIKE NICHOLLS

It most probably affects the development of the left and right side the brain and if you're exposed to more testosterone maybe than normal then the right hemisphere of the brain will develop more compared to the left.

Narration

The way Mike tells it, the right hemisphere takes on more of the workload, including handedness. And since it’s testosterone we’re dealing with, it may explain why more males are left handers. By the same token Mike reasoned that left-handed females might appear more masculine too. A student survey confirmed they were more likely to label themselves as “tomboys”.

DR MIKE NICHOLLS

Also left handers tend to have a different body shape compared to right handers in that they tend to have less wide hips and wider shoulders compared to others.

It’s only a very small difference. So in a sample of forty people you know there's only most probably a difference of half a centimetre or so.

GEOFF BURCHFIELD

In a line up for example you couldnít pick out the left handers?

DR MIKE NICHOLLS

No, no, I don't think so.

Narration

Mike acknowledges there are other causes of left-handedness including stress at birth.

DR MIKE NICHOLLS

At least in some cases I would suggest that...some sort of brain injury around birth period or pre natally ah gave rise, caused damage to the left side of the brain and caused the person to become right hemisphere dominant and therefore left handed.

Narration

In the last thirty years, many studies have lumped left-handedness in with a rag tag assortment of ills and psychoses.[autism, bed-wetting, brain damage, depression, drug abuse, dyslexia, gullibility, immune disorders, migraines, schizo-phrenia, school failure, low life expectancy] How many of these are genuine..... ? Ask a left-hander.

DR MIKE NICHOLLS

Well I think quite a few of them are real. I should point out that you know left handers aren't a seething mass of you know criminals or anything like that but if you look at the sort of large statistics they do suggest this. So for example yes you are more likely to find left handers amongst populations of stutterers and dyslexics. You are more likely to even find more left handers amongst inmates of prisons.

Narration

But left-handers aren’t all crims. Statistics also show that many of the world’s great thinkers, artists, musicians and inventors have been left-handed including Alexander the Great, Julius Caesar, Leonardo da Vinci, Michelangelo, Beethoven, Napoleon, Albert Einstein, Charlie Chaplin, Marilyn Monroe, Bill Clinton, and Bart Simpson.

Dr JAMES STEELE, University of Southampton

The pattern of life here in medieval times was dominated by agriculture. The occupants of the majority of the households here would have been peasants. Juvenile mortality was high perhaps a half of the skeletons recovered from the cemetery of individuals who died before reaching adulthood.... So there must have been a lot of personal tragedies in these households.

Narration

Although the last inhabitants of Wharram Percy died 300 years ago James Steele suspects they took their handpreferences with them to the grave.

Dr JAMES STEELE, University of Southampton

This kind of hard physical work leaves its mark on the skeleton. The type of labour may also enable us to detect whether one or other hand was being used preferentially in what you might call power or hard tasks, because the bone responds to mechanical strain in various adaptive ways that we can pick up when we examine the skeletons.

Narration

The remains of 122 men and women took a ride to this lab in Southampton. Steele discovered striking differences between left and right.

Dr JAMES STEELE, University of Southampton

(EXAMINING A SKELETON LAID OUT ON A TABLE) In this individual if you look at the collar bones we see on this right side... the ligament’s been doing much more work and we can see this from the way in which the surface of the bone has become modified in response to those strains. This was a right-handed individual.

(MOVES TO SECOND SKELETON) And on this individual we can see handedness from the overall size of the right and left humerus. In this case the right humerus is far longer than the left, indicative of increased mechanical strain on that side while the bone was growing.

Narration

Steele concluded that about 15 percent of the villagers were left-handers, more than might be expected from modern figures. Perhaps here in the simpler time of Wharram Percy, it’s possible to see a natural underlying level of left-handedness that today is masked by culture. It isn’t just from looking back to an earlier time that we find this natural level of handedness. Chris McManus at University College, London, believes that we should also look at the earliest stages of our life.

Prof CHRIS McMANUS, University College London

Foetuses of course sit in the foetal position, their hands up like this, and they do what all babies do; they suck their thumbs. And you can see them sucking their thumbs on the ultra ah the dynamic ultra sound records. And 90 percent of babies suck their right thumb. Ten percent of babies suck their left thumb. Now that's clearly not learned its not environmental or anything like that. So I think there's a lot of evidence here weíre dealing with something that's inbuilt built and its biological rather than something which is um merely learned or social or due to environmental problems or whatever.

Narration

According to Chris the origins of handedness will be found in our genes...although it’s not as simple as one gene for right-handedness and another for left.

Prof CHRIS McMANUS, University College London

Well we think basically there's a gene for right handedness which accounts for the fact that most people are right handed. And so most of us have a double dose of this right handed gene, and that makes us right handed and that's straight forward.(sync from here*) But the other gene is not a left handedness gene in any simple sense. Instead it’s what we call a chance gene. And people who have a double dose of this chance gene do not end up as either right hand or left hand. They have a fifty/fifty chance of being right or left handed. It’s as if a coin is being tossed and the brain will only go this way or that way. And it could be either way. There's no control there at all.

Narration

The theory predicts that 75% of people will have the right-handed gene. And half of the rest will end up right-handed by chance. This means that just 12 and a half percent of the population will be left-handers, which is pretty close to what we actually find. Identical twins have been hard to explain. It’s not uncommon for one to be left handed, and the other right even though they have exactly the same genes. Chris’ answer is that they have the chance gene.

Prof CHRIS McMANUS, University College London

One twin tosses a coin and goes one way and the other twin can toss the coin in uterus and go the other way. And when we do the mathematical calculations we get almost exactly the proportions weíd expect.

Narration

Assuming such a gene exists it’ll probably affect many things other than handedness, including language.

Anecdotal story from Melbourne architect, DAVID ISLIP

Well my father's story is quite interesting. When he was at school, in primary school, they actually noticed he was writing with his left hand and they ended up forcing him to write with his right. And the impact that that had was I suppose quite interesting in so far as not only did the teacher go about and rap him across the knuckles with the ruler for doing that but it also started to effect his speech - he started to stutter. And also when it came to actually writing, for example, in Geography when it would have say a dot showing where Melbourne was heíd write Melbourne but it would be the mirror image.

Narration

Many people have noticed a connection between handedness and language. Michael Corballis sees it everywhere, even on the morning ferry. Many people have noticed a connection between handedness and language. Michael Corballis, a cognitive psychologist at the University of Auckland, sees it everywhere, even on the morning ferry.

Prof MICHAEL CORBALLIS, University of Auckland

Well I think first of all handedness is not in the hands. I mean there’s no way to look at somebody’s hands and decide whether they’re left or right handed. So handedness is in the brain...Something like 98 percent of right handers have language controlled on the left side and I think it would be very surprising if there were not a link there. My view is that language is very much dependent on the hands...

Narration

You only have to look at the gestures we use to embellish conversation. And if our hearing is impaired we use sign language to replace the spoken word. In fact research has verified that whether we use voice or hands to communicate, we use exactly the same part of the brain. And it may have been that way in humans for a very long time.

Prof MICHAEL CORBALLIS, University of Auckland

Presumably when the hominids diverged from the African apes about five million years ago they were much better equipped to develop communication systems based on the hands because there's already a good deal of voluntary control and sophistication in what they can do with their hands whereas vocally they were probably not capable of doing much more than grunting. So I think if language evolved in the course of hominid evolution it almost certainly started with the hands.

Narration

There may even be supporting evidence from the animal world. Although individual dogs, cats and mice have a favourite paw, overall half will be left and half right. The peanut butter game is a favourite.

GEOFF BURCHFIELD & BILL

Bill what reaction are you hoping to get by giving them these tubes?

Narration

The idea is to see which hand the chimps use to extract the peanut butter.

BILL & GEOFF Sync:

GEOFF: Bill, how many chimps are you finding are using a left hand as opposed to right hand?
BILL: It’s about a two to one ratio; of right-handers to left-handers. So roughly there’s 15 or 16 chimpanzees in here and ten right handers, five left-handers and maybe one ambidextrous....
GEOFF: So the right hand rules but it’s not exactly the same as with humans?
BILL: Exactly.(CHIMP SCREAMS)

Narration

But is there more to this hand preference than meets the eye? Bill checked his chimps into Atlanta’s Emory Hospital and took multiple brain scans....especially of that region on the left side that in humans islinked with language and some say righthandness.

BILL

Okay. For example, here if I take that area and now blow it up a bit and we look clearly or more closely at this area.

Narration

Here was the same fingernail-sized structure as in humans, though not so well developed. Does this mean chimps should be able to chat? Well, in a way some already can. Several have been trained to converse using a vocabulary of 200 hand signals. And if language is linked to handedness then maybe chimpanzees are right handed for the same reason as humans.

Chris McManus thinks that by figuring out how handedness evolved we’ll get a fresh perspective on where we’re headed. We know when our ancestors opted for the right from the tools they made. Each time a flake is struck off, the core is rotated one way or the other. That gives away the toolmaker’s hand thousands of years after the event.

And ancient skulls and plaster casts of the brain cavity tell us when left and right sides started to look and act differently. From that a timetable emerges for the development of language and the ascendancy of the right-hand.

Prof CHRIS McMANUS, University College London

Most animals are fifty/fifty right handers/left handers. Two million years ago all humans became right handed - that's one hundred percent of them and that had its advantages. And then about a hundred thousand years or so ago another mutation occurred which meant that left handedness could come into being and it must have had some advantage to it and left handers have stayed around since then. So they’re there not because they're an evolutionary throw back to a primitive state, but because they're a recent mutation with additional advantages. Now what they are is anybody guess.

Narration

So, maybe left-handers are a new improved model human. If so, what are the improvements? Many claims have been made about the creative potential of the right brain. But only a few of them bear closer inspection.

Prof MICHAEL CORBALLIS, University of Auckland

The right side of the brain probably has more to do with spatial perception, spatial awareness, and things that are emotional. So there’s some evidence that the right side of the brain is more sensitive to emotional expression.

Narration

Although left-handers aren’t all creative geniuses there is one profession where a visual flair may be at work.... Daryl Jackson is one of Australia’s most highly regarded architects. Around one third of the architects in his team are left-handers.

DARYL Sync:

Some architects are highly technical, very strong project-directed, management-oriented architects. And there are others that are highly design-conscious, intuitive people. And in many instances this latter quality happens to be accompanied by a left-handed view.

Narration

The advantage of left over right is more tangible in competitive sport. Tennis, for example, has had more than it’s share of great southpaws. Mc Enroe, Connors, Navratilova, Seles, and our own Neale Fraser.

FRASER Sync:

I think left handed in tennis is a big advantage. ....A left hander probably plays ninety percent of their matches against right handers. So the right hander’s facing a left hander only ten percent of the time. And, and that's the awkwardness of the left hander. Two left handers don't like playing each other because they play each other less.

Narrration

When opponents are close together the left-handers’ game is lifted. Their unusual angle of attack isn’t a hindrance. It’s a real advantage. In fencing around one third of competitors at world championship level are left-handed. But this sporting edge isn’t a special gift. It’s simply the element of surprise. It would evaporate if left-handers were more common. Science is presently unable to say whether it was culture or genetics that produced left-handedness in the first place. But some evidence may be just around the corner.

Like us, mice have their heart on the left side, off centre. That asymmetry must be controlled by a gene. It’s thought that the gene that lets our brain be asymmetric and makes us handed may be very similar.

Prof CHRIS McMANUS, University College London

One of the most exciting things that's come up in the last six months is that very recently the gene which makes the heart of mice be on the left side has been found and it’s been sequenced. And my prediction therefore is that now once now we know that gene, if we start searching through the genome for similar genes then we’ll find something else in the human genome which we won’t find in the mouse genome. And that's going to be that gene that makes us right handed and left handed. So I think that could give us a fast track through to finding the gene for handedness.

Narration

Finding a gene would confirm that handedness is part of our biological make-up and through its links with language offer new insights into the human condition. One final thought. Parrots. They’re handed too. And there’s evidence that their verbal dexterity is also controlled by the left side of the brain.

Prof MICHAEL CORBALLIS, University of Auckland

Oh yeah. Parrots have always been a problem actually parrots have a tendency to pick things up with the left claw left foot um ah and the bias is about ninety percent so that's the nearest thing I've ever been able to discover in in another species that approaches the degree of bias that humans have. So we may be descended after all from parrots.

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