THIS STORY HAS BEEN FORMATTED FOR EASY PRINTING

Politics aside, these presidents are lefties

By David Brown
Washington Post / March 24, 2009
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Five of the last seven presidents have been left-handed: Gerald Ford, Ronald Reagan, George Bush the elder, Bill Clinton, and now Barack Obama.

So what does this mean in a world where 1 in 10 people, roughly speaking, is a lefty?

The answer is . . . nobody knows. It may be a fluke. But even if it isn't, exactly what left-handedness has to do with political skill, intelligence, popularity, family connections, wealth, and luck - all at play in our selection of national leaders - is almost certainly a matter of subtle advantage, not one of dramatic benefit.

What is clear is that "handedness" runs all through the animal world.

Once thought to be uniquely human, some version of this attribute has been seen in chimpanzees, marmosets, cats, chickens, toads, mice, rats, and almost certainly thousands of other species. It is present in animals that don't have hands, such as fish, and in some that don't have backbones, such as honeybees.

In biology, this phenomenon is known as "lateralization." It is the preference for doing or perceiving things more with one side of the body than the other. It appears to be an important - although perhaps not necessary - consequence of having a brain.

Like many structures in the body, the brain is bilaterally symmetrical. It is made up of two halves, called hemispheres, divided by a plane that makes one the mirror image of the other.

Lateralization saves space and, therefore, working capacity, by not requiring that both hemispheres do the same thing. It diminishes the chance of interference and confusion, which might arise if each side of the brain independently analyzed the same input from the environment and came up with its own decisions about what to do about it. It also allows the brain to sometimes do two things at once.

"Any brain seems to lateralize if it can," said Lesley Rogers, a longtime researcher in the field who is an emerita professor at the University of New England in Australia.

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