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States With a Higher Percentage of Right-Handed Residents Tend to Lean Republican

In describing political preference, "right" and "left" may be more than a metaphor.
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A woman holds her voting sticker in her hand after casting her ballot in Leetonia, Ohio.

Given the intensity of the political debate at the moment, it seems like a good time for a lighter, quirkier perspective on our ideological divide. So here goes: New research suggests our shorthand terms of "left" and "right" to indicate liberal and conservative viewpoints just may have biological roots.

"States with higher levels of left-handedness among their residents tend strongly to have greater preference for the Democratic party," writes psychologist Stewart McCann of Canada's Cape Breton University. Conversely, those with fewer lefties are more likely to vote Republican.

As he writes in the journal Laterality, the correlation is quite large, and not easily explained.

McCann used data from a 2009 study to estimate the percentage of left-handed residents in each of the 48 contiguous states and the District of Columbia. Each state's dominant political ideology was determined using two factors: a series of CBS/New York Times polls in which participants were asked whether they saw themselves as liberal, moderate, or conservative; and the percentage of residents who voted for the Republican presidential candidate in each election from 1996 through 2012.

He found a very clear pattern. "State levels of left-handedness correlated to an extremely high degree with conservative/Republican presence," he writes.

After taking into account such factors as each state's racial mix and socioeconomic level, the link between the two was smaller but still substantial.

"Two predictors—handedness and socioeconomic status—could account for 71 percent of the variance in state (ideological) preference," he reports. "Handedness alone could account for 63 percent of the variance."

A follow-up study found that, when handedness was factored into the equation, the well-established link between various personality traits and the tendency to be a liberal or conservative disappeared.

As McCann emphasizes, there is no evidence that, on an individual level, a right-handed person is more likely to be a Republican, or vice-versa. So what explains these findings? He points to poorly understood genetic factors.

Perhaps, he writes, ideology and personality are shaped by the same genetic factors that lead to left- or right-handedness, but the link to the latter is stronger in some people than others.

There is also speculation that left- and right-handed people enjoy different levels of communication between the hemispheres of their brains; such differences could conceivably influence political orientation. (A stronger connection between the two has been linked to greater creativity.)

Solving this mystery, and better understanding the link between personality, ideology, and genetics "has profound implications for the dynamics of democracy," McCann concludes.

Indeed, at a time when we're clinging tightly to our tribes, it's good to be reminded that the biological basis of our beliefs and affiliations remain poorly understood. If you think that's a good reason to be a bit more tolerant of the other side, raise your hand.