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| Do left-handed people really die young? | Do left-handed people really die young? |
| (about 11 hours later) | |
| There's an often-quoted statistic that right-handed people live on average nine years longer than left-handed people. As the daughter of two left-handed parents, and the sister of a left-handed brother, this, to me, is a rather worrying idea. But is there any truth in it? | There's an often-quoted statistic that right-handed people live on average nine years longer than left-handed people. As the daughter of two left-handed parents, and the sister of a left-handed brother, this, to me, is a rather worrying idea. But is there any truth in it? |
| The finding was advanced in two articles in the late 1980s and early 1990s by American psychologists Diane Halpern and Stanley Coren - both published in prestigious scientific journals, Nature and the New England Journal of Medicine. | The finding was advanced in two articles in the late 1980s and early 1990s by American psychologists Diane Halpern and Stanley Coren - both published in prestigious scientific journals, Nature and the New England Journal of Medicine. |
| But what could the explanation for the premature death of left-handers possibly be? | But what could the explanation for the premature death of left-handers possibly be? |
| Something to do with the fact that tools are not designed for them? | Something to do with the fact that tools are not designed for them? |
| "Knives are very awkward," says Claire Allen from Hampshire in southern England. | "Knives are very awkward," says Claire Allen from Hampshire in southern England. |
| "They are designed for right-handers - if you use it as a left-hander it cuts on the slant all the time, whereas for a right-hander it cuts straight." | "They are designed for right-handers - if you use it as a left-hander it cuts on the slant all the time, whereas for a right-hander it cuts straight." |
| I know that my mother would be bereft without her special left-handed sewing scissors. | I know that my mother would be bereft without her special left-handed sewing scissors. |
| But surely nothing like this could be responsible for cutting life short by almost a decade? | But surely nothing like this could be responsible for cutting life short by almost a decade? |
| "It's not at all plausible," says Chris McManus, professor of psychology and medical education at University College London and the author of Right Hand, Left Hand. | "It's not at all plausible," says Chris McManus, professor of psychology and medical education at University College London and the author of Right Hand, Left Hand. |
| "If this were true it would be the largest single predictor we had of life expectancy - it would be like smoking 120 cigarettes a day plus doing another of other dangerous things simultaneously. It really is highly implausible that an epidemiologist wouldn't have spotted it previously." | "If this were true it would be the largest single predictor we had of life expectancy - it would be like smoking 120 cigarettes a day plus doing another of other dangerous things simultaneously. It really is highly implausible that an epidemiologist wouldn't have spotted it previously." |
| If it's so implausible why was it published in respected academic journals and why has the myth endured? | If it's so implausible why was it published in respected academic journals and why has the myth endured? |
| Because, according Chris McManus, the researchers made a "very subtle error". | Because, according Chris McManus, the researchers made a "very subtle error". |
| The studies were conducted in Southern California, where lists are published of everyone who has died. | The studies were conducted in Southern California, where lists are published of everyone who has died. |
| Halpern and Coren took a list of the people who had recently died and contacted their families, asking whether or not their relative had been right- or left-handed. | Halpern and Coren took a list of the people who had recently died and contacted their families, asking whether or not their relative had been right- or left-handed. |
| Looking at 2,000 cases, they saw that the average age at death of the left-handers was about nine years younger than of the right-handers. On that basis, they concluded that left-handers died earlier. | |
| At first glance, that seems persuasive. What did the researchers do wrong? | At first glance, that seems persuasive. What did the researchers do wrong? |
| "Their mistake was that they only looked at the dead," Chris McManus explains. | "Their mistake was that they only looked at the dead," Chris McManus explains. |
| The point is that left-handers are more common now than they used to be, so - at least at the time the research was published - left-handers were on average younger than right-handers. | The point is that left-handers are more common now than they used to be, so - at least at the time the research was published - left-handers were on average younger than right-handers. |
| "The natural rate of left-handedness is around 10% or 11%, but the rate was pushed down artificially during the Victorian period," says Chris McManus. | "The natural rate of left-handedness is around 10% or 11%, but the rate was pushed down artificially during the Victorian period," says Chris McManus. |
| "You can see it going down from about 1800 onwards through to about 1900." | "You can see it going down from about 1800 onwards through to about 1900." |
| Not only would left-handed people have been encouraged not to be during this period, life was also pretty difficult for them and they quickly became very conspicuous. | Not only would left-handed people have been encouraged not to be during this period, life was also pretty difficult for them and they quickly became very conspicuous. |
| "They went to work in factories using machines designed for right-handers - and the left-handers looked awkward," says McManus. | "They went to work in factories using machines designed for right-handers - and the left-handers looked awkward," says McManus. |
| "And then compulsory schooling came along and they were obliged to sit in classrooms and try and write with their right hand using an ink pen and they made a mess. The result of all of this was that left-handers became stigmatised - regarded as cack-handed, stupid." | "And then compulsory schooling came along and they were obliged to sit in classrooms and try and write with their right hand using an ink pen and they made a mess. The result of all of this was that left-handers became stigmatised - regarded as cack-handed, stupid." |
| So, some of the people who had died on those Californian lists may well have been born left-handed, but spent most of their lives acting and identifying as right-handers. Their families would have described them as such, when the researchers came knocking. | So, some of the people who had died on those Californian lists may well have been born left-handed, but spent most of their lives acting and identifying as right-handers. Their families would have described them as such, when the researchers came knocking. |
| This would have skewed their results. | This would have skewed their results. |
| To see why, imagine an exaggerated scenario where there were no left handers at all born before 1973 - 40 years ago. | To see why, imagine an exaggerated scenario where there were no left handers at all born before 1973 - 40 years ago. |
| If we now look at death records for 2013 and ask who, among the dead, was left-handed we would see that all of them died at or before the age of 40. That would be much younger than the average of age at death of right-handers. | If we now look at death records for 2013 and ask who, among the dead, was left-handed we would see that all of them died at or before the age of 40. That would be much younger than the average of age at death of right-handers. |
| Nothing like this exaggerated scenario ever occurred in reality - but the number of people identifying as left-handed did grow dramatically during the 20th Century. | Nothing like this exaggerated scenario ever occurred in reality - but the number of people identifying as left-handed did grow dramatically during the 20th Century. |
| So the idea that left-handers die nine years earlier than right-handers is a myth. | So the idea that left-handers die nine years earlier than right-handers is a myth. |
| What about non-fatal injuries? Should we be worried about people like Claire Allen struggling in the kitchen with knives designed for the right-handed? Or my own mother for that matter, if she were forced to use right-handed scissors? | What about non-fatal injuries? Should we be worried about people like Claire Allen struggling in the kitchen with knives designed for the right-handed? Or my own mother for that matter, if she were forced to use right-handed scissors? |
| "There is some evidence that left-handers are more likely to have minor accidents," says Chris McManus. | "There is some evidence that left-handers are more likely to have minor accidents," says Chris McManus. |
| "But it's pretty insubstantial and I doubt if it's affecting the mortality rate very much at all." | "But it's pretty insubstantial and I doubt if it's affecting the mortality rate very much at all." |
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