Two people with opposite opinions listen to the same report, and both hear confirmation of their preexisting beliefs. The reaction seems almost automatic, and in a sense it may be. Psychologists at Emory University tested thirty men in the months before the 2004 presidential election. Half were strong Democrats, and half were strong Republicans. The men were hooked to MRI machines and then asked to listen to and assess clearly contradictory statements from George W. Bush and John Kerry. The brain scans showed that as the subjects processed what the candidates said, they essentially turned off the sections of th brain associated with reasoning. Meanwhile, the scans revealed lots of activity in the parts of the brain associated with emotions, pleasure, and judgments about morality. "We did not see any increased activation of the parts of the brain normally engaged during reasoning," psychologist Drew Westen said. "What we saw instead was a network of emotion circuits lighting up...Essentially, it appears as if partisans twirl the cognitive kaleidoscope until they get the conclusions they want, and then they get massively reinforced for ir, with the elimination of negative emotional states and and [the] activation of positive ones"
Via Nonlinear Droppings.