The industry devoted to increasing the turnout of voters -- all those green eye shade types in Washington think tanks, those young voter consortiums with Xes and Zs to denote "coolness" -- they may want to pick up the latest issue of Scientific American and read about the experiments of James Fowler, a political scientist at the University of California at San Diego.

It turns out that self-interest may motivate people to vote as much as many experts (and virtually every practicing political consultant) believes.

Monozygotic and dizygotic twin studies are a staple of experimental psychology and developmental biology. Dr. Fowler wondered whether there was a way to test whether the willingness to vote -- or, rather, voting behavior -- can be correlated with genetic variation. (Remember, identical twins -- monozygotic -- are genetically identical; dizygotic twins share roughly 50 percent of their genes.)

By studing the voting behavior of these twins, Fowler found that "genetics was responsible for 60 perceent of differences in voting turnout between twin types, with the rest coming from environmental factors or other factors." A larger sample found a similar correlation.

Another scientist found a smaller correlation, one similar to the correlation usually found for "genetically influenced personality traits in general."

I'm a little skeptical. I'd love to see a study of voting behavior among genetically identical twins who were separated at birth; that way, the environmental factors are better segretated. Also: there's not really a neat separation between environmental and biological influences; if you're a biologically cranky child, your parents will probably treat you as they would treat a cranky child, and your aggregate level of crankiness interacts with environment.

My guess is that a propensity to vote is probably linked to a personality trait like cooperation or sociability. In another study, Fowler found that one's penchant for altruistic behaviors and the degree to which people are motivated to help others in their group also drive people to increase their political participation. (Here's a bet: someone in Barack Obama's inner circle has read this study.)

What does this mean for political consultants: instead of trying to turn all young voters into new voters, it'd be more efficient to target those young voters whose parents were voters. But then you're dealing with another environmental effect: the degree to which the content of a parent's political worldview influences their offspring's.

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