Confirmation bias is a human problem. It afflicts throughout the range of political perspectives.
Brain imaging research indicates some aspects of individual political orientation correlate significantly with the mass and activity of particular brain structures including the right amygdala and the insula. This correlation may derive in part from genetics, but is also influenced by environment and behavior.
“there’s a critical nuance here. Schreiber thinks the current research suggests not only that having a particular brain influences your political views, but also that having a particular political view influences and changes your brain. The causal arrow seems likely to run in both directions—which would make sense in light of what we know about the plasticity of the brain. Simply by living our lives, we change our brains. Our political affiliations, and the lifestyles that go along with them, probably condition many such changes.”
Thanks to member, Edward, for recommending this article: http://www.motherjones.com/politics/2013/02/brain-difference-democrats-republicans
In a similar vein, Bob Altemeyer conducted and reported on some seminal social science research and theory on political dispositions. See http://home.cc.umanitoba.ca/~altemey/. Note the free book link on the left.