A few weeks before the 2008 election, Democratic strategists were running out of ideas for how to help Al Franken. His race against incumbent Minnesota senator Norm Coleman was a stubborn one: Even after some of the country’s highest ever per capita spending, the contest remained close, with a small number of undecided, seemingly unbudgeable voters.

The job of pollsters in these situations is to figure out who the undecided actually are and what could make them move. Often, they focus on demographics (playing to older suburban women) or issues (talk of school reform). But one pollster working for the Democratic Senatorial Campaign Committee, Mark Mellman, felt it might pay to look for more primal distinctions.

Mellman added to his Minnesota polls a battery of questions inspired by research in psychology and neuroscience, borrowed from personality tests and designed to separate those with more rational processing systems from those who relied on emotion in their decision-making. Here polls did discern a latent split: Franken led Coleman by one point among those they identified as “feelers” but lagged by seven points among “thinkers.” The committee changed its ad strategy in response. Highly stylized television spots, like a movie spoof that showed Coleman as a fugitive fleeing George W. Bush, were replaced by messages that were “a little more flat, a little more factual, a little more sourced,” Mellman said. One defended Franken against Coleman’s charges with a calm narrator reading off a checklist of straightforward rebuttals under the words “The Truth.” Franken won, after a long recount, and in 2010 Mellman used the same battery of questions to shape media strategy for Harry Reid and Barbara Boxer.

That kind of science may seem alien to the war room, but Mellman’s hunch, that the differences in how people process politics may be more innate than we’ve thought, is becoming the default assumption in research labs worldwide. There, over the last decade or so, scientists have been extending to politics the imperious insights of neuroscience and evolutionary psychology that have so shaken other social sciences.

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