Dick Meyer in a CBS News column summarizes research that has been done on the processing of contradictory information within the brain. His summary says:
"When 30 self-described partisans were presented with contradictory quotes about the candidates (President Bush supporting, then denouncing Ken Lay; Sen. John Kerry supporting, then denouncing a Social Security overhaul), it was the portions of the brain that process emotion, not rational thinking, that became active. "The thinking caps went off and the feeling caps went on," is how Westen [the researcher] put it to me.
Normally, Westen says, a brain faced with contradictory information will fire up the zones where reason or rational thought happens. The 30 partisans in this study were presented with contradictory quotes from Bush and Kerry, but also from Hank Aaron, Tom Hanks and the writer William Styron. They processed the information about the non-politicians with the reasoning centers of the brain. It was politics that short-circuited them. ("This is your brain; this is your brain on politics.")
It would be reasonable to ask whether all brains — not just partisan ones — respond to political information emotionally. Westen says the answer is clearly no, that research does demonstrate that centrists or independents are more able to process rational and non-emotional political information."
Even worse, the other researcher that Meyer discusses says that the number of partisans is increasing!