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The notion that liberals are smarter than conservatives is familiar to anyone who has spent time on a college campus. The College Democrats are said to be ugly, smug and intellectual; the College Republicans, pretty, belligerent and dumb. There's enough truth in both stereotypes that the vast majority of college students opt not to join either club.

But are liberals actually smarter? A libertarian (and, as such, nonpartisan) researcher, Satoshi Kanazawa of the London School of Economics and Political Science, has just written a paper that is set to be published in March by the journal Social Psychology Quarterly. The paper investigates not only whether conservatives are dumber than liberals but also why that might be so. (See the top 10 political gaffes of 2009.)

The short answer: Kanazawa's paper shows that more-intelligent people are more likely to say they are liberal. They are also less likely to say they go to religious services. These aren't entirely new findings; last year, for example, a British team found that kids with higher intelligence scores were more likely to grow into adults who vote for Liberal Democrats, even after the researchers controlled for socioeconomics. What's new in Kanazawa's paper is a provocative theory about why intelligence might correlate with liberalism. He argues that smarter people are more willing to espouse "evolutionarily novel" values  that is, values that did not exist in our ancestral environment, including weird ideas about, say, helping genetically unrelated strangers (liberalism, as Kanazawa defines it), which never would have occurred to us back when we had to hunt to feed our own clan and our only real technology was fire. (See the top 10 religion stories of 2009.)

Kanazawa offers this view of how such novel values sprang up in our ancestors: Imagine you are a caveman (if it helps, you are wearing a loincloth and have never shaved). Lightning strikes a tree near your cave, and fire threatens. What do you do? Natural selection would have favored the smart specimen who could quickly conceive answers to such a problem (or other rare catastrophes like sudden drought or flood), even if  or maybe especially if  those answers were unusual ones that few others in your tribe could generate. So, the theory goes, genes for intelligence got wrapped up with genes for unnatural thinking.

It's an elegant theory, but based on Kanazawa's own evidence, I'm not sure he's right. In his paper, Kanazawa begins by noting, accurately, that psychologists don't have a good understanding of why people embrace the values they do. Many kids share their parents' values, but at the same time many adolescents define themselves in opposition to what their parents believe. We know that most people firm up their values when they are in their 20s, but some people experience conversions to new religions, new political parties, new artistic tastes and even new cuisines after middle age. As Kanazawa notes, this multiplicity of views  a multiplicity you find within both cultures and individuals  is one reason economists have largely abandoned the study of values with a single Latin phrase, De gustibus non est disputandum: there's no accounting for taste. (See pictures of John 3:16 in pop culture.)

Kanazawa doesn't disagree, but he believes scientists can account for whether people like new tastes or old, radical tastes or Establishment ones. He points out that there's a strong correlation between liberalism and openness to new kinds of experiences. But openness to new experience isn't necessarily intelligent (cocaine is fun; accidental cocaine overdose is not).

So are liberals smarter? Kanazawa quotes from two surveys that support the hypothesis that liberals are more intelligent. One is the National Longitudinal Study of Adolescent Health, which is often called Add Health. The other is the General Social Survey (GSS). The Add Health study shows that the mean IQ of adolescents who identify themselves as "very liberal" is 106, compared with a mean IQ of 95 for those calling themselves "very conservative." The Add Health study is huge  more than 20,000 kids  and this difference is highly statistically significant. (See the top 10 scientific discoveries of 2009.)

But self-identification is often misleading; do kids really know what it means to be liberal? The GSS data are instructive here: Kanazawa found that more-intelligent GSS respondents (as measured by a quick but highly reliable synonym test) were less likely to agree that the government has a responsibility to reduce income and wealth differences. In other words, intelligent people might like to portray themselves as liberal. But in the end, they know that it's good to be the king.

The jury may be out on whether conservatives are less intelligent than liberals, but there's evidence that they may be physically stronger. Last year, the Proceedings of the National Academy of Sciences published a fascinating paper by Aaron Sell, John Tooby and Leda Cosmides of the Center for Evolutionary Psychology at the University of California at Santa Barbara. The authors measured the strength of 343 students using weight-lifting machines at a gym. The participating students completed questionnaires designed to measure, among other things, their proneness to anger, their history of fighting and their fondness for aggression as a way to solve both individual and geopolitical problems.

Sell, Tooby and Cosmides found that men (but not women) with the most physical strength were the most likely to feel entitled to good treatment, anger easily, view themselves as successful in winning conflicts and believe in physical force as a tool for resolving interpersonal and international conflicts. Women who thought of themselves as pretty showed the same pattern of greater aggression. All of which means that if you are a liberal who believes you're smarter than conservatives, you probably shouldn't bring that up around them. You might not like them when they're angry.

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