The Science of Handedness

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.'"

I've followed these studies forever...

[smoothnorman]

Just a few years ago, a Canadian study using baseball stats (because they tracked handiness closely) concluded that lefties were far more likely to die, ( http://www.nejm.org/doi/full/10.1056/NEJM199110033251412 [nejm.org]) this was later shown to have suffered a seemingly paradoxical sampling error (not controlling adequately for those that didn't die). Then there was another study that concluded that left-handedness was likely the result of anoxia in the womb ( http://www.sciencedirect.com/science/article/pii/002839327390050X [sciencedirect.com]). It was discounted for similar sampling error problems. Neurological "wiring error"; perhaps a mutation with few consequences; advantages in the mathematical world (presumably via having a screwy mindset); Language disadvantages; Language *advantages*; high proportion of left-handed (possibly suppressed) American presidents http://www.anythingleft-handed.co.uk/presidents.html [anythingle...nded.co.uk] (Clinton, Bush, Obama ... ). So... run a elaborate predator/prey model applied to sports and see an advantage for the 10% that are different; sounds like rediscovery of Perato distribution to me, http://en.wikipedia.org/wiki/Pareto_distribution [wikipedia.org] I'm just not convinced that there's been a proper scientific approach to this issue to date, and until then i'm still stuck with a twisted spine in most college classrooms.

Re:Good question!

[silentcoder]

I'm the child of two right-handed people - and I'm neither, I'm one of the 1% ambidextrous people - but I prefer to write with my left hand.

Re:So why the right hand?

[dcollins]

Writing, scissors, buttons, car shifter (first few I thought of in 10 seconds).

In particular, writing: It's designed that right-handers are dragging the writing implement behind their hand in a smooth gliding motion. For left-handers we're smashing the point into the page in front of our hand, making it highly variable and irregular (a non-equilibrium), and then also smearing the hand over what we just wrote. Truly a pain. That's specifically the reason why my uncle (for example) was forced to switch by my grandparents tying his left hand behind his back.

And personally, I think that writing is the most important of all human tools.

Re:Good question!

[Pandur77]

All I can say is that I'm left-handed. Both my parents are right-handed and so are both my brothers.

Re:So why the right hand?

[Phroon]

Luckily, the physicist has since discovered another clever experiment which the aliens can use to differentiate between what we call matter and antimatter. There's a certain type of particle that can transform into it's antiparticle and back again. But the catch is that one of the transformations will happen more often than the other. That means that even if the alien swaps matter for antimatter they will still be able to tell which is which by looking at which transformation dominates. (More details here [wikipedia.org])

"Now," the physicist admits "this all assumes that the aliens haven't swapped the direction of time on us as well! Buggers might just have effects preceding causes." (See CPT symmetry [wikipedia.org])