Democrats and Republicans alike are adept at making decisions without letting the facts get in the way, a new study shows.

And they get quite a rush from ignoring information that's contrary to their point of view.

Researchers asked staunch party members from both sides to evaluate information that threatened their preferred candidate prior to the 2004 Presidential election. The subjects' brains were monitored while they pondered. . . .

"We did not see any increased activation of the parts of the brain normally engaged during reasoning," said Drew Westen, director of clinical psychology at Emory University. "What we saw instead was a network of emotion circuits lighting up, including circuits hypothesized to be involved in regulating emotion, and circuits known to be involved in resolving conflicts." [Emphasis mine]

The test subjects on both sides of the political aisle reached totally biased conclusions by ignoring information that could not rationally be discounted, Westen and his colleagues say.

Then, with their minds made up, brain activity ceased in the areas that deal with negative emotions such as disgust. But activity spiked in the circuits involved in reward, a response similar to what addicts experience when they get a fix, Westen explained.

The study points to a total lack of reason in political decision-making.

"None of the circuits involved in conscious reasoning were particularly engaged," Westen said. "Essentially, it appears as if partisans twirl the cognitive kaleidoscope until they get the conclusions they want, and then they get massively reinforced for it, with the elimination of negative emotional states and activation of positive ones."

Notably absent were any increases in activation of the dorsolateral prefrontal cortex, the part of the brain most associated with reasoning. . . .

This research is a warning to all decision-makers, not the least of which are investors. It's important to know whether you're interpreting facts, or whether your network of emotion circuits are lit. The latter can cost you a lot of money.