Baseball Players and Handedness
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This week’s Skeptoid episode is about left-handedness. Not about the popular anecdotes you can read on any web site, but about the deeper science behind how and why left-handedness exists at all, and what the implications are for those who roll to the left.
Skeptoid is a short program and I can’t ever include all the neat stuff I uncover, so occasionally I’ll throw a supplemental bit here. This week I found one tidbit that was particularly interesting that I wasn’t able to squeeze into the show. A crazy tidbit that I did discuss in detail was that left-handers gradually die out of the population faster than right-handers: the older the age group you sample, the smaller percentage of lefties you’ll find. By age 90, living left-handers are practically nonexistent. This isn’t because they change over and become right-handers, it’s because they literally die out of the population, due to a combination of risk factors associated with sinistrality.
A factor that complicates this field of study is that handedness of people who die is very hard to determine; death certificates don’t include whether the person was left-handed or right-handed, nor do almost any other medical records. Researchers have to telephone the next of kin and ask to get each and every data point.
But two of the field’s most notable researchers, Stanley Coren and Diane Halpern, came up with a novel way of getting this data, albeit for a limited population: The Baseball Encyclopedia. Baseball players are one group whose handedness, along with date of birth and date of death, are meticulously tracked by enthusiasts. Coren and Halpert limited their survey to those players who were either strongly left-handed or strongly right-handed (as indicated by both throwing and batting hands) and who did not change handedness during their careers.
Despite weaknesses in this type of sampling (for which they were roundly criticized by other researchers, and to which they did respond in print), the results they found very much agree with the best numbers still being observed today. 2.5% of right-handers survived to at least 90 years of age, while only a fifth as many, 0.5%, of left-handers did. Beyond the age of 33, they found a consistent difference of 2% between the percentages of surviving sinistrals and surviving dextrals.
These results remained consistent even when Coren and Halpern trimmed the most extreme 5% of outliers in the data to eliminate skewing of the results due to players whose lifespans were on the long tails of the bell curve.
It turns out that being left-handed has a shockingly significant correlation with early mortality. On average, worldwide, dextrals live nine years (!!) longer than sinistrals, so this research is perhaps much more important than most of us would have guessed.
There are complete references for this on the Skeptoid transcript page, in addition to much deeper discussion of the causes and effects of left-handedness.
Ouch… maybe there’s something to be said for teaching young kids to be right-handed. (My parents did that to my siblings, who used to be left-handed, but now prefer their right hands for most tasks.)
Or could it be contra-productive? There’s always the law of unintended consequences and it could be that people whose preferred hand is different from their innate preferred hand are clumsier, although when it comes to clumsy in our family, not my siblings but yours right-handed truly takes the biscuit.
I wonder if there are statistics on where left-to-right-handed people lie, in comparison with either left- or right-handed people. I also wonder what typically causes the excess deaths; what happens to people who die because they’re left-handed? The world doesn’t seem to be particularly hostile to them, but maybe it’s some subtle effect, like maybe they don’t make as much money and hence eat worse and cannot afford as good health care. In that case, I wonder if focussing on a sub-population that’s relatively atypical of the whole could be skewing the statistics.
Retraining may help to reduce one identified cause of reduced longevity, which is accidents; but not the others.
One problem with looking at the general population is that some of the older people were forced to be right handed. My grandfather was one of those (died at 72) who was then equally bad with both hands and his writing was terrible. Changing someone’s handedness is a bad idea. I did see somewhere that a lot of left handed people die because of accidents. Well it is a right handed world. Everything is designed to be run with your right hand in control (except for driving a manual car, left hand on the wheel, right on the shift) so if you can’t adapt it puts you in awkward situations leading to more accidents, less control of power tools,…
I wonder if the traffic accident rate is different in countries like UK where the shift is in the left hand and the right on the steering wheel?
>Changing someone’s handedness is a bad idea.
You have your anecdote, but on the other hand my cuneiform doesn’t even begin to compare with the beautiful handwriting of my siblings. And it isn’t just writing either; anything from housework to hobbies… if it’s a manual task, they excel at it, both in speed and accuracy.
I’m not looking for anecdotes, but data, and I cannot seem to find any.
How strange! Is handedness a genetic trait? It would seem to be, since there is a fairly consistent drive to teach people to write with the right hand as the default. If it were indeed learned you would expect to see almost 100% conformity, which we do not.
The next obvious question is what the mechanism might be for earlier lefty mortality. I am at a loss to come up with anything, but there are the stats. Fascinating stuff.
The Skeptoid episode linked at the beginning of the post goes into this in detail.
Would strokes paralyzing the left hand have anything to do with it?
Also, uhoh…….better start writing righty.
That is so interesting I wonder if there is a way to prevent this.
I read of this and wondered what really killed them. I mean the act that made the death. Is it really accidents? Would the strong eye matter if the world were made for the other eye?
To the best of my knowledge thee are no records kept in the UK as to the handedness of drivers involved in road accidents. (I was a police officer in the UK for 30 years)
Both my parents, as well as my brother and myself, were/are left-handed. My father died at the age of 62 and my mother at the age of 81, but they were both smokers. My brother is 73 (and a smoker) and I am the baby of the family at 66 ;o) (I am the only non-smoker, but I do have a cardiac malfunction, which is electrical). My only real issues are approaching old age, gravity, and an awareness of the length of the journey. (34% of live births in the UK do not reach the age of 65)
I can remember that my mother had a specific concern that I might be made to write with my right hand (or at least hold the implement in it)but, neither my brother nor I had this problem.
I am right side dominant when catching something or kicking a ball, but left side dominant when writing, using a spoon, shooting (target pistol) and fencing – that’s with a sword. So I class myself as ambiguous (sic).
Just to note in finishing that no-one in our family, irrespective of gender or age has ever reached 90 years of age which, let’s face it, is a great age; but I wouldn’t mind being the first providing I still have all my marbles. Should I ever lose those I might not want to keep playing.
Thanks Ian, but this data could easily be obtained by interviewing accident victims or their relatives in the case of fatalities. It may be that there is no effect and shifting is simply a cultural thing with no impact on accidents, but I’ve always thought that I could not possibly shift with my left hand–which I never use for single-handed activities and awkwardly for even two-handed activities. I often joke that I must be right-brain dead because my left hand is so weak.
Your hand doesn’t do much other than grip gently when shifting gear so manual dexterity isn’t an issue. The shifting is done from the elbow by the muscles in the upper arm.
I remember that some time ago a postal history collector (someone who collects the stamps that are still on the envelope – showing the address and the cancel) told me that he could sometimes tell if the postmaster was left handed or right handed by the subtleties in the postmark. In other words, the postmark of a right handed postmaster would be slightly darker on the right hand side of the postmark due to the way he held the canceler. You would need a lot of envelopes from before 1900 to check this out — after that time, many envelopes were cancelled by machine. The early postmasters of all US post offices are recorded as to their time in service. I wonder if there is a list of birth/death dates as well.
My father was born left handed but was taught in school to be right handed. He felt quite pleased to find himself ambidextrous leaving him able to use which ever hand was most suited to the task at the time. He lived to a ripe old age, so maybe that’s the answer.
A quick look at the “related citations” link on PubMed’s page for Coren and Halpern’s study (http://www.ncbi.nlm.nih.gov/pubmed/2006231) reveals that the existence of a handedness-longevity correlation is far from a settled matter. It’s for precisely this reason that a single study doesn’t make something scientific fact. Quite a few researchers have found no correlation between handedness and longevity at all, one group even when using the same data as Coren and Halpern. There is nothing approaching consensus on this topic.
Interesting to note the stated life expectancy of male lefties ( 62 years )
When I was young I was cajoled/bullied/bribed and belittled in an attempt to make me use the “correct ” hand, to no avail.
I consider myself to be clumsier than average & have used my handedness as a good excuse many times.
It has always seemed to me that the way we hold our cutlery is natch for lefties; anyone else feel this way ?
Hopefultom ( 65 year old leftie )
As British comedian Lee Evans once said; “I’m ambidextrous, I can do sod all with both hands!”