Well, I've read about various studies from the past few years where new neuroscience tools are being used to watch people's brains as they make decisions. What these studies show is that people who self-identify as being conservative are not very good at dealing with new information.
See:
What Makes People Vote Republican?
What makes people vote Republican? Why in particular do working class and rural Americans usually vote for pro-business Republicans when their economic interests would seem better served by Democratic policies? We psychologists have been examining the origins of ideology ever since Hitler sent us Germany's best psychologists, and we long ago reported that strict parenting and a variety of personal insecurities work together to turn people against liberalism, diversity, and progress. But now that we can map the brains, genes, and unconscious attitudes of conservatives, we have refined our diagnosis: conservatism is a partially heritable personality trait that predisposes some people to be cognitively inflexible, fond of hierarchy, and inordinately afraid of uncertainty, change, and death. People vote Republican because Republicans offer "moral clarity"—a simple vision of good and evil that activates deep seated fears in much of the electorate. Democrats, in contrast, appeal to reason with their long-winded explorations of policy options for a complex world.
Democrats and Republicans Both Adept at Ignoring Facts, Study Finds
The study points to a total lack of reason in political decision-making.
Study finds left-wing brain, right-wing brain
...scientists have found that liberals tolerate ambiguity and conflict better than conservatives because of how their brains work.
Why we vote the way we do
For both the 2000 and 2004 elections, the analysis showed that negative perceptions of Democratic candidates Al Gore and John Kerry were more pivotal in putting a Republican in the White House than were positive perceptions of George Bush.
Update 9/19/2008 - more stories about the Conservatives' mental defect:
Left, Right; Obama, McCain: It may not be what you think
Conservatives Scare More Easily Than Liberals, Say Scientists
Update 9/26/2008
What's the difference between a liberal and conservative?
Political conservatives operate out of a fear of chaos and absence of order while political liberals operate out of a fear of emptiness, a new Northwestern University study soon to be published in the Journal of Research in Personality finds
Update 9/30/2008
Two Genes Predict Voter Turnout
In this article, we hypothesize that people with more transcriptionally efficient alleles of the MAOA and 5HTT genes are more likely to vote. An association between a gene and political behavior may also be moderated by environmental factors. This phenomenon is known as a gene-environment (GxE) interaction (Shanahan and Hofer 2005). We therefore also hypothesize that an association between each of these genes and voting may be moderated by social activity. Using data from the National Longitudinal Study of Adolescent Health, we conduct gene and gene-environment association tests on the relationship between turnout and MAOA and 5HTT. The results show that both genes are significantly associated with the decision to vote. Moreover, the association between 5HTT and turnout is moderated by exposure to religious social activity. These findings have important implications for how we both model and measure political interactions.
