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Math Science

The Science of Handedness 258

Hugh Pickens writes "Representing only 10 percent of the general human population, scientists have long wondered why left-handed people are a rarity. Now a new study suggests lefties are rare because of the balance between cooperation and competition in human evolution and a mathematical model was developed that predicts the percentage of left-handers by sport based on each sport's degree of cooperation versus competition. 'The more social the animal—where cooperation is highly valued—the more the general population will trend toward one side,' says study author Daniel M. Abrams. 'The most important factor for an efficient society is a high degree of cooperation. In humans, this has resulted in a right-handed majority.' If societies were entirely cooperative everyone would be same-handed, but if competition were more important, one could expect the population to be 50-50 because cooperation favors same-handedness—for sharing the same tools, for example while physical competition favors the unusual. In a fight, for example, a left-hander would have the advantage in a right-handed world. The mathematical model accurately predicted the number of elite left-handed athletes in baseball, boxing, hockey, fencing, and table tennis (PDF)—more than 50 percent among top baseball players and well above 10 percent (the general population rate) for the other sports. For other sports like football or hockey where team cooperation is paramount, it is ideal for all individuals to possess the same handedness. For example, in football, blocking schemes are often designed to protect a quarterback's blind side. As a result, it is beneficial for all quarterbacks on the roster to possess the same handedness to minimize variations of the offensive sets. 'The accuracy of our model's predictions when applied to sports data supports the idea that we are seeing the same effect in human society.'"
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The Science of Handedness

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  • by cpu6502 ( 1960974 ) on Sunday April 29, 2012 @04:50PM (#39839385)

    Why isn't everyone left-handed? That too would be beneficial in a cooperative society (shared tools). Maybe millions of years ago, the left-handed tribes died out. (Maybe they called themselves Neandertals.)

  • by CSMoran ( 1577071 ) on Sunday April 29, 2012 @05:07PM (#39839463) Journal

    Why isn't everyone left-handed? That too would be beneficial in a cooperative society (shared tools).

    This probably reflects the assymetries in the human body (heart on one side, one lung smaller, etc). Anyway, if all was in reverse and the majority were left-handed, you'd be here asking "Why isn't everyone right-handed?" :).

  • Re:What tools? (Score:4, Interesting)

    by The_mad_linguist ( 1019680 ) on Sunday April 29, 2012 @05:07PM (#39839465)

    Single bevel axes are 'handed'.

    I imagine optimizing the grip would also cause some handedness as well.

  • by icebike ( 68054 ) * on Sunday April 29, 2012 @05:30PM (#39839623)

    are like the wolves amongst you right-handed sheep, right!!!!???

    I'm not ENTIRELY convinced, what about situations where it is advantageous for people to have opposite handedness for optimal cooperation? There seems to be a built-in assumption here that different-handed assortments of people will always have more problems working together. I'm not sure there's a practical way to test this as a general thing though.

    I agree, the theory is weak.

    Using sports as a model for why handed-ness exists is putting the cart before the horse. That Baseball was able to capitalize on left handed pitchers throwing to much more common right handed hitters is a rather late innovation in the annals of human endeavor.

    Further, very few tools existed in historical times where handedness mattered at all. A wrench or a hammer or a spear have no handedness. Only much later were tools invented to meet the needs of the majority or users, which is why there was a tendency to put controls on power tools on the right.

    The whole thesis mistakes cause for effect, suggesting tools and games we invented had something to do with what made us what we are. Whether our ancestors threw the spear, or picked the berry right or left handed couldn't have mattered at all.

  • Re:Well, no... (Score:4, Interesting)

    by Frequency Domain ( 601421 ) on Sunday April 29, 2012 @06:04PM (#39839813)

    You joke, but that was literally true for me w/ regards to handwriting. Then one day my second grade teacher saw me switching hands and freaked out. She made me sit on my left hand for the rest of the year and had the colossal gall to tell me that someday I'd thank her for it. When my doctor learned about it at my next annual physical, he was pissed off beyond belief. He didn't cuss, but he kept muttering about "superstitious morons" and "subjecting kids to the prejudices of idiots", or words to that effect.

    Fortunately the only thing impacted was my handwriting. Fifty years later my left-handed writing still looks like a first-grader while my right-handed writing got arrested at a second grade level. But I'm one heck of a typist, when I played soccer I did equally well on either left or right wing, I'm popular at dinner parties because I can accommodate whoever I am seated next to without bumping elbows, and my wife thinks I'm a very versatile fellow.

  • Re:Good question! (Score:5, Interesting)

    by AJWM ( 19027 ) on Sunday April 29, 2012 @06:14PM (#39839875) Homepage

    I have (fraternal) twin sons. One is right handed, one left handed.


  • by FrootLoops ( 1817694 ) on Sunday April 29, 2012 @06:26PM (#39839919)

    if you ever meet a perfect version of yourself constructed by aliens from radio transmissions, don't shake their hand.

    For those who don't know, this refers to a story in the Feynman Lectures on Physics. Here's my version; I've taken some liberties.

    Imagine you're on the phone with an alien who speaks English, except they don't know what "left" and "right" mean. You want to explain it to them so they know which tentacle they should use to shake the right-handed President's hand if they should ever meet. The alien can be anywhere in the universe, so you can't refer to stellar positions or similar, leading you to devise an experiment for them to perform.

    Your initial attempts use gravity, electricity, and magnets, but you notice each experiment comes out essentially the same if you swap "right" and "left"--for instance, you could give the alien instructions for making a clock in hopes of defining "right" using clockwise rotation, except if the alien made the clock exactly backwards by reversing the notion of "left" and "right", they wouldn't be able to tell. A particle physicist happens by and tells you about a magical experiment involving the weak nuclear force that *does* distinguish left and right inasmuch as the experiment fails if the alien screws up "right" and "left" and succeeds otherwise. (For the curious, some more details here [] and here [].) Great, problem solved.

    "But wait!" the physicist says. "The alien needs to use regular matter instead of antimatter in the experiment. The results will be reversed otherwise! Come to think of it, I have no idea how to tell them the difference between matter and antimatter. If you ever meet them and they start trying to shake your left hand, RUN, since the alien will be made of antimatter!"

Don't tell me how hard you work. Tell me how much you get done. -- James J. Ling