Why Am I Left-Handed?
Tim Dowling finds out what makes people left-handed. Also what advantages and disadvantages left-handedness can bring. With Professor Chris McManus and Ed Wright.
Tim Dowling 0:18
Hello, and welcome to Insult My Intelligence. In today's episode, we investigate left handedness, why it exists? And whether being left handed is really that different. We'll speak to a professor of psychology who's been studying handedness for decades, and an author of a book that explores some of the great left-handed people throughout history. But first, let me declare an interest. I'm left handed and so are two of my three sons. In this household, there is a distinct left handed majority. But this is admittedly a small sample size, I wanted to know the global size of the left handed population.
Chris McManus 0:55
Those are very large study came out of what about a year ago, and probably 9 to 10% is a pretty accurate figure. It's a bit lower in some places where handedness is still suppressed. And probably China's one of those
Tim Dowling 1:11
This is Chris McManus, a professor at UCL and the author of right hand left hand, the origins of asymmetry in brains, bodies, atoms and cultures.
Chris McManus 1:21
But 10% is not far. But there's the interesting thing, it's more common in men than women. And my usual description is that there's five left handed men for every four left handed women. And we don't know why that is, but that seems to be pretty universal as well.
Tim Dowling 1:41
And why? Why are more people right handed? I mean, why isn't it? Why doesn't it come out roughly even?
Chris McManus 1:49
Okay, I always say, there's there will be three possibilities. One, if if, if it was chance, then there wouldn't be really much to explain. So it's just a coin being tossed at some point. And that's roughly the way it is in a lot of animals, as far as we can tell. They prefer to use one paw one hand, but half of them use the right, half of the use the left, so that would be the easiest thing to explain. The second easiest thing to explain is, if it was like our heart now, almost all of us have our heart on the left side of our body, as about one in 10,000 who have their hearts on the right. But if everybody were right handed, then that would be relatively easy to explain. But really hard is why we're mostly right handed, but one in 10 of you guys are left handed.
Tim Dowling 2:37
And it's not the people who have their hearts on the wrong side of their body. Is there any correlation between that?
Chris McManus 2:44
No, we did a study on that a while ago, there's a condition called primary ciliary dyskinesia, which makes your heart sometimes be on the wrong side of the body, it's actually a chance thing. So half of them have their heart on the right side, half on the left side. But we followed them up, and they have same rates of left handedness as the rest of the population. So that's separate as far as we can tell. It's probably deeply related, in some sense, I suspect, because I think probably the reason we're right handed ultimately is because our heart is on the left. First of all, our body went asymmetric. And we got genes to do that. And then later, our brain picked up some of those genes, modified them, adapted them, and then started to make our brain asymmetric. So they deep down, they're probably related biologically. But at the moment, we haven't got a good account of that.
Tim Dowling 3:37
It's one thing to ask why left handed people exist in the first place, and another to ask why we still exist and still persist as a relatively stable proportion of the global population. One idea is that being left handed confers some real evolutionary advantages, both physical and mental, but it's a competitive edge that's only retained as long as you're in the minority. Here is the author of a left handed history of the world. Ed, Wright. Ed, you've written a book on some of the great people throughout history, who are left handed all the way from Ramses ll to Jimi Hendrix. So I'm guessing you don't think it's just some sort of coincidence.
Ed Wright 4:21
I think, you know, left handers sort of unorthodox people. I mean, they estimate that around 10% of the population and that's a fairly consistent percentage, are left handed at any given time in the history of humanity. And that confers certain disadvantages, but is also conferred certain advantages, and part of that, I think, is the way left handers natively and cognitively interpret the world in a different way, but also, the way they're forced to adapt to a world which is essential set up for right handers.
Tim Dowling 5:02
Sports is a place where left handers kind of predominate in a lot of ways even though they they're obviously a minority. You know, tennis players, baseball players, cricket players, they have they have a kind of advantage in sports. Something like pitching a we we can find a statistic that in the last decade 28% of baseball innings were thrown by lefties. You know, what is it that gives sports people an advantage as left handers? Is it just surprise?
Ed Wright 5:37
I think it begins with surprise. And it begins with not quite fully understanding the angles that the ball will come from. And that certainly in a baseball pitching and the other thing is bowling in cricket. You know, the two obvious examples of that. If you go back, one of the reasons they argue in terms of kind of evolution for the survival of left handedness is it did give people an advantage in battle to some extent, by virtue of that idea of surprise, in that you expect somebody to hit you with the right hand and they come at you with the left. And you know that way, there was an argument that, for instance, that the practice of shaking hands began you know, as a way of neutralising the battle arm. And then, but it's nice if you're shaking hands politely with the right and your left hander and you don't like that person and you can clock them nicely with your left. Not kind of exactly good etiquette necessarily, but advantageous nonetheless.
Tim Dowling 6:50
But Chris McManus thinks a lot of these stories of battlefield advantages for left handers are just that stories. Someone was telling us that left handed people were very handy for fighting on circular staircases, because their sword hand was able to reach round on their way up. I don't know if that's true is that because because the
Chris McManus 7:09
it's one of the lovely bits of folk mythology that stayed around. The variant of the story is that those people in Scotland had the surname Kerr or Carr, because that meant sort of cack handed in effect. And they were meant to live in left handed castles so that they could fight their way down the stairs. A student of mine once did a wonderful thing in the, in the days when there were London telephone directories. He simply phoned up about 100 people who were called Kerr or Carr. And then 100 people who were called something else and asked them if they were right or left handed, and if their family or and so on. And there was no evidence that they were right up more likely to be left handed. But the story carries on.
Tim Dowling 7:51
I mean, people have been not so much now. But people have been really persecuted over the years or denied preferment or whatever. I mean, it's there's a long history of this isn't there.
Chris McManus 8:02
So for instance, you know, I had an email the other day from actually a left hand who had been forced to be right handed. And he was in relatively late life. And he was saying that, and I think this has changed the whole of my life. Everything has gone wrong before because of it. Now, it wasn't clear. And it's certainly not clear from the research that that is the case. But it's very easy to use it as an explanation for events not going well. Very rarely left handers. Sometimes nowadays, left handers say, Well, of course, I'm a successful architect, because I'm left handed I was thinking differently. That's becoming quite a common trope as well.
Tim Dowling 8:39
Chris McManus 8:39
And I suppose in the Middle Ages or something, if you were looking for witches, then, you know, it was one of the witch marks, it was something they looked for. And therefore you could see how it gets used. So that's one thing is just visible difference. I think another thing is there is a sense in which we're back to standardisation. When you come through to the 19th century, then what you're finding is firstly, factories are being set up. And these have got, you know, Spinning Jenny's and all these other things in them, and they're all built one way round. And of course, they're built for right handers, they're not going to make 10% of them left handed. So suddenly you're finding a group of people who are visibly less capable of using the machines. Similarly, when you start going to schools and you have compulsory education, people are starting to sit there with their slate, or worse still with a pencil with a pen, and they're writing on paper, and they're using a steel pen which is dipped into ink, and you try pushing it across the paper as a left hander. It's impossible you just make a mess everywhere. So they looked upon as less capable in fact they are because the task is intrinsically much harder, but they come visibly different once more. And there's an insinuation of lack of competence if you like. So you can see where you get people, let's say stereotypes start to form.
Tim Dowling 10:08
One thing is certain, a historical insistence that everybody be taught to write with their right hand, regardless of inclination, made school a miserable place for some otherwise very talented people for a very long time.
A lot of the people I like, in terms of artists and writers, and and inventors, in your book, had one another thing in common, which is they, they were terrible at school, or they left school very early. But and this could possibly be a consequence of maybe not doing well, because they're left handed.
Ed Wright 10:45
Yeah, and this might be going back to the time where you were, you had to write with your right hand. So, you know, school was something that kind of contained your best instincts in a way. And, you know, was something that sort of forced you into something that was unnatural with yourself, and then, you know, to an extent you're surviving, outside of that, you know, your talents were kind of growing in a different way, outside of that environment. You know, and there's a lot of, I think, you know, one of the things that has been noticed about left handed because of the right hemisphere dominance, dominance, sorry, in the brain, is that there's tends to be a lot of that mathematical and music and scientific thinking going on in, you know, that that tends to be not exclusively, but centred in the right hemisphere of the brain. So a lot of the great left handed geniuses tend to excel in those sorts of activities.
Tim Dowling 11:46
Left handedness is also a reflection on the way your brain works in the first place. But the differences are subtle and complicated. And by no means the same for every left handed person, Chris McMahon is is a professor of psychology, so I wanted to ask him in all important question about left handers? Are we smarter than right handed people? Or does it just, you know, feel that way?
Chris McManus 12:08
This short answer to are they smarter is probably know, the slightly longer answer is probably slightly less smart. But the longer answer still is that when you measure it the on standard IQ test, the difference is something like a quarter to a half of a point. So if you have 100,000 people in a study, you can find it. But apart from that, no, you can't. So for all practical purposes, there's no difference. No. So that's IQ, which is, you know, not the nest necessarily the best of measures. Um, they might well think differently. We know we know, our brain, the left handers brains are different in some way. Or let me rephrase that some left handers have brains which are different. So for instance, I know I'm right handed, and I know I'm talking to you, with the left half of my brain, the whole thing crosses over my right hand is controlled by the left half of my brain. And I know I'm talking to you with the left half of my brain because I've had it scanned, so I know what's going on in it. Now, left handers, they're not the mirror image of that, remarkably, about most left handers are actually like me, they have language in the left half of their brain is on the same side as their hand, not on the opposite side as their hand. And about that about 30% actually have it the other way around. So left handers are much more variable in their neural organisation that seems to apply when you look at other things, you know, where, which bit of the brain use for face recognition or for understanding prosody, you know, language and that sort of thing. There's a whole load of these tasks. And Lang, left handers are much more variable. Now, we suspect and there's not much 100% proof of that, that being more variable is a good thing when you're not very much more variable. But it's a bad thing when you're a lot more variable. So, you know, if you're all shook up, then it's probably not going to work very well. But if a few things just happened to be nudged into different places, you can get some happy accidents where suddenly you find you've got a relationship between bits of the brain that other people don't have. And that could be advantageous.
Tim Dowling 14:36
How do we I mean, do we know this might be a dumb question. Obviously left, there's an extent to which left and right brains are wired differently. But in terms of your handedness, do we have a notion of how much room on that side, you're having a dominant hand takes. ,
Chris McManus 14:54
We have a little bit um, and one of the nice Ssudies, it must be 20/25 years ago now when fMRI scanners were really coming in and we could look at brain functioning. And they were looking at professional violinists. And if you look at the cortex, where in the hand region, it's possible to identify a bit of cortex corresponding to each of the fingers okay, so this five little patches there. And that tells you where those fingers are being driven from. But if you look at professional violinists, particularly on their left hand, it would be their left hand, they had larger, more separated areas, because of course, they're doing all sorts of fast, rapid things with their left hand, wasn't there on the right hand, because they just going Boom, boom, boom, with the bow backwards and forwards. And whilst that's very skilled, it's not doesn't need the five fingers to be acting differently. So occasionally, with something like that, you can see bits of the brain responding in order to, to get slightly larger to do things slightly better. But I think probably in most of us, it's not very obvious now.
Tim Dowling 16:11
Not very obvious, it's not scary, being left handed isn't squeezing something out that we could otherwise be doing with?
Chris McManus 16:17
Neh, I don't think so. I wouldn't worry
Tim Dowling 16:20
Thats me putting it as scientifically as I can. What about those achievements or skills that don't have anything to do with your hands? Do left handers have any kind of advantage when it comes to something like say, leadership?
When we talk about musicians and sports figures, we're talking about left handness just being which hand they are is of huge consequence and direct consequence, I suppose.
Ed Wright 16:46
Tim Dowling 16:47
When we talk about generals, or or world leaders, we're talking about something more subtle. I mean, it's not because they write with their left hand or because they, you know, they have certain visual way of looking at the world that makes them gives them an advantage.
Ed Wright 17:02
That's a bit of a harder one, I think. And I think, in a way, why, I suppose, left handers in an evolutionary sense, a kind of risk takers. But as a consequence of that, you know, they're more likely to go pear shaped as well. And so, you know, for instance, you know, there's a higher proportion of people who are left handed with schizophrenia, for instance, right, and certain kinds of mental illnesses and disabilities, I think there might even be a higher percentage of left handed people. And I'm, you know, I couldn't be exact about these statistics who might be alcoholics or something like that. But then there does seem to be a kind of a very high proportion. And in my book, the statistic that I found most interesting about this was I only got as far as Obama but and I think Donald Trump was a right hander. He's hopefully is a right hander.
Tim Dowling 18:05
I would almost guarantee it!
Ed Wright 18:09
but that of the the Presidents before that Obama was a left hander, and Bill Clinton was a left hander. And Ronald Reagan was a left hander. And George W. Bush was a left hander. And I think even Gerald Ford might have been a left hander as well. So you had this enormous stretch of kind of left handed people presiding over at what was that time, you know, that I suppose the, the greatest power in the world? And you say, You wonder what makes somebody get to there, you know, and, and often, it takes a sense of exceptionalism, I suppose, to have the drive to, you know, reach that kind of point of power, and, and, and within your own society. And I think, you know, America is interesting, in a way, in that it's always had that belief of people coming from nowhere to become the president. And you can kind of see that, you know, in the story of Obama, for instance, or even Bill Clinton, you know, who came from troubled family and stuff like that. So, I think it's something about that made me think about, you know, whether that sense of being different in the world is something that psychologically and I, you know, how do you measure an effect like this, allows you to put yourself apart from the world as a way of getting to the top of it.
Tim Dowling 19:55
A lot of times left handedness is associated with a lack of hand eye coordination. But then you've got people like Da Vinci and Michelangelo, who are sort of extraordinary in their ability to kind of just make marks on paper.
Ed Wright 20:11
here, and there is something about that visual, you know, which again, feeds into that sort of right hemisphere of the brain linking to, you know, the ability to think, you know, conceptually in terms of spatially, like, for instance, is very important in music and mathematics as well. And some of those great visual artists, you know, the ability to sort of paint or you know, draw into space in certain ways, you know, that we, you know, Michelangelo and Leonardo da Vinci. And you know, Leonardo da Vinci was somebody who was never ashamed of the fact that he was left handed, and, you know, sort of view one of the most originally organised people perhaps who ever lived.
Tim Dowling 20:50
And finally, I wanted our guests view of what the future holds for the left handed population. So I guess my final question is if if those kind of social if the social stigma is really has faded as we sort of as it seems to be steadily fading and and we're, we learn more about it, and people are allowed to write the way they want to write and we, you can buy a left handed guitar for 50 quid, yeah. is are we going to lose that advantage? Or is are the left hand persons distinct? If rarified advantages in society, are they going to fade?
Ed Wright 21:29
That's a really interesting question. I suppose the sense of having to struggle, knowing you were different, in some ways, will fade. At the same time, the world is still set up, in a way for right handers. So as you learn things, and, you know, we learn so much by imitation. And so, that process from the beginning of learning how somebody does something, and then switching it around in your head, may preserve that sort of slight, you know, cognitive difference in a way. And I think perhaps, the other thing that may persist is because left handers have do have greater variability in their kind of, I suppose, the, the, the makeup or structure of their brains than right handers. Then, in a way, they they might be, they might evolve slightly differently as well. So it's a great question, but you know, I really don't know what the answer will be. But one can only guess and hypothesise.
Tim Dowling 22:56
I asked Professor McManus, if left handed people could ever go extinct.
Chris McManus 23:01
I think the opposite. I think there was a time we did some historic we're trying to it's quite difficult to get out decent historical data on it. But it looks as if about 10% of people at the beginning of the 19th century were left handed. And that rate went down and down until about 1890, perhaps 1900. Till in Britain, it was down to about 2-3%. And we speculated that that was due to the the Industrial Revolution and universal education. So left handers found they had problems. But since then, once the 20th century came, it rose up quite rapidly. And interestingly, by the end of the Second World War, it was back up to 10%. And it stayed at that level of since. And people are suggested it was actually getting into the army it it let people be what they wanted. They weren't stuck in a village where they were told off for being left handed or something. So it was a great equaliser and a provider of freedom if you like. But I think you know, it's been that layer for half a century. I don't see it changing dramatically.
Tim Dowling 24:10
I suppose you as you mentioned, there are other countries where it's still frowned upon or taught against. And in the future we may see the overall percentage of people that leads to openly admit to being left handed rise more.
Chris McManus 24:24
Yeah, I think so. The Chinese are interesting because there's data on Chinese Americans at the turn of the 20th century, and only about 2% of them were left handed. And you can see the rate of left handedness in Chinese Americans going up and up until it becomes 10% the same as everybody else in America. In China, it stayed low. And that's because there was social pressure. But the one that the thing that's changing in China is quite intriguing is ping pong. Because of course, this is a sport which is immensely prestigious, and they rapidly realised that the left hand has had a strategic advantage. And so you see loads of people playing ping pong, left handed and International Olympic level. And the result is that other people are saying, Oh, well, maybe left handed isn't so bad after all. And, but when you then follow them through, I do a lecture some Chinese students every year, and I have a photograph of one of the women whose left handed table tennis player, and then she's there signing her awkward autographs with her right hand. And it sort of summarises the issues, there's pressures in both ways. I think we'll find the whole world but become 10% left handed, that's my prediction. There we go.
Tim Dowling 25:47
I was never made to write with my right hand as a child. And when it came to sport, I was permitted to choose the first time I picked up a tennis racket, I didn't know what to do. It felt equally unwieldy in either hand, and to be honest, it still feels that way. I bet right and throw left, I play the guitar and the banjo like a right hander. And I wouldn't be able to work a pair of left handed scissors, I've adapted to your right handed world without much difficulty. And maybe when I think about it without that much success, either. I can't say I've ever been discriminated against for being left handed. And before now, I've never considered the possibility that my brain might work differently. I mean, I don't know how anybody else's brain works anyway. But there doesn't seem to be any escape from the fact that we are as humans, fundamentally asymmetric beings. The concepts of left and right are embedded in us, their internal.
Chris McManus 26:43
Mach, the philosopher physicist, he said that only an asymmetric organism can actually distinguish right and left. And that seems to be the case there's a lot of animals that can't truly distinguish left and right. And that's because they're probably not a symmetric enough to have the ref an internal reference to tell them which is which we do you have that internal reference, or are these external? You know, it's like Freud used to say if he wants to know which is the right he tries to write, yeah, it doesn't work in German. Of course, it's a joke, but there we go. But he still tried to do it. He'd make some quick scribbling motions, and that would tell him where right and left was, but you have to be a symmetric in some way.
Tim Dowling 27:26
Thanks for listening to this episode of insult my intelligence and thanks to my guests Chris McManus and Ed Wright. Please leave us a rating and review. You can follow us on Twitter @insultmyintel and if you have an idea or a topic for an episode, do email us at email@example.com Next week we're talking about revitalising dying languages.