The left brain knows what the right hand is doing

Browse through a list of history's most famous left-handers and you are likely to see Albert Einstein's name. You may even see people tying Einstein's genius to his left-handedness. The problem is, Einstein's left-handedness is a myth. Myriad photos show him writing on a chalkboard with his right hand, for example.

But handedness has its roots in the brain—right-handed people have left-hemisphere-dominant brains and vice versa—and the lefties who claim Einstein weren't all that far off. While he was certainly right-handed, autopsies suggest his brain didn't reflect the typical left-side dominance in language and speech areas. His brain's hemispheres were more symmetrical—a trait typical of left-handers and the ambidextrous.

By comparison, 95 percent of righties have brains that strictly divvy up tasks: The left hemisphere almost exclusively handles language and speech, the right handles emotion and image processing—but only about 20 percent of lefties have brains that divide up these duties so rigidly.

Brain hemisphere specialist Michael Corballis, PhD, a psychologist at the University of Auckland in New Zealand, points out that having the hemispheres manage different tasks might increase the brain's efficiency.

"There's an advantage to cerebral dominance because it localizes function to one hemisphere," he says. "Otherwise, information has to cross back and forth across the corpus callosum, and that can sometimes cause problems."

A strongly symmetrical brain, like Einstein's, leaves people open to mental dysfunction, but it also paves the way for creative thinking. Researchers are exploring these unusually balanced brains and finding out why that's the case.

Righties rule

About 90 percent of people are right-handed, says Corballis. The remaining 10 percent are either left-handed or some degree of ambidextrous, though people with "true" ambidexterity—i.e., no dominant hand at all—only make up about 1 percent of the population.

That means the vast majority of people on this planet have strongly lateralized brains. That's probably no accident, Corballis says. Early in human history, and possibly even in our pre-human ancestors, evolution delegated different cognitive responsibilities to the brain's two hemispheres, he posits. It would be inefficient for both sides to, for example, process a person's speech when one hemisphere can do that just fine on its own. That frees up the other hemisphere to do something else, such as sort out the speech's emotional content.

Researchers used to think that minor brain damage early in development caused left-handedness, he notes.

"But if that's true, that's probably the minority of cases," Corballis says. There are just too many lefties for brain damage to be the major culprit, "so we look to genetics."

In 2007, geneticists identified a gene on chromosome 2, LRRTM1, that seems to be present in most lefties (Molecular Psychiatry, Vol. 12, No. 12). The gene has also been linked to schizophrenia, which fits with earlier research showing that people with schizophrenia are significantly more likely to be left-handed or ambidextrous.

Less-lateralized brains may also be linked to lower IQ scores, suggests a study by Corballis, published in Neuropsychologia (Vol. 46, No. 1). The study found that left-handers and right-handers had similar IQ scores, but people who identify as ambidextrous had slightly lower scores, especially in arithmetic, memory and reasoning.

These results dovetail with Corballis's previous findings that ambidextrous people also rate higher on a "magical ideation" scale, which measures people's propensity to, for example, think that people on television are talking directly to them or that they can sense when people are talking about them (Laterality, Vol. 7, No. 11).

The link among these three findings—the slight propensity for schizophrenia, lower IQ scores and magical ideation—may suggest that the brain is more likely to encounter faulty neuronal connections when the information it's processing has to shuttle back and forth between hemispheres, says Corballis.

Ambidexterous payback

"That poses an evolutionary question," Corballis says. "If this [right-handed] gene is so advantageous, why are there still left-handers?"

Research suggests that there might be a big advantage to a less constrained brain: It might lead to less constrained thinking.

For years, anecdotal evidence has suggested that lefties might think more creatively than right-handers, and recent research supports this link. A 2007 paper in Journal of Mental and Nervous Disease (Vol. 195, No. 10) found that musicians, painters and writers were significantly more likely to be left-handed than control participants.

Corballis has a theory as to why: Just as information is prone to errors as it traverses between brain hemispheres, it's also more likely to encounter novel solutions. Righties might dismiss an idea as too radical, but nonrighties might be willing to entertain the thought nonetheless, and develop a solution that a right-hander's brain would skip right over.

"It's good to have a few people in any society who think outside the square," Corballis says.

Left-handers are taking that creativity straight to the bank, too, says Christopher Ruebeck, PhD, an economist at Lafayette College in Easton, Pa. In a study published in Laterality, he found that lefties earn slightly more money than their right-handed peers who work at the same jobs. These results were most pronounced in left-handed college-educated men, Ruebeck says, who, on average, earn 15 percent more than righties. In fields where creative thinking is valuable, lefties might get the edge and earn more accordingly.

"Left-handed men seem to get a higher return on their education," he says.

The study found this effect in men but not in women, Ruebeck adds, though he's unsure why that might be. And because his study is one of only a few that have looked into this area so far, he cautions against overgeneralizing these results; at the moment, it remains an interesting correlation.

Also, equating left-handedness with creativity glosses over the fact that 20 percent of left-handed people do have strongly lateralized brains and are probably no more creative than right-handers. The idea of lefties as creative types "probably refers to the subgroup of [left-handers] who lack clear dominance in the hemispheres," Corballis says.

So what's the final verdict? Well, in a way, the human condition itself might be summed up as the balance between the brain's asymmetries and symmetries—rationality versus creativity, novel ideas versus traditional solutions.

"The asymmetrical brain might even represent science and the symmetrical brain, religion," Corballis speculates. "An exaggeration, no doubt, but it's fun to think along these lines."