Hard-wired to blog

At long last, the scientific basis for the political blogosphere.

Using M.R.I. scanners, neuroscientists have now tracked what happens in the politically partisan brain when it tries to digest damning facts about favored candidates or criticisms of them. The process is almost entirely emotional and unconscious, the researchers report, and there are flares of activity in the brain's pleasure centers when unwelcome information is being rejected.

"Everything we know about cognition suggests that, when faced with a contradiction, we use the rational regions of our brain to think about it, but that was not the case here," said Dr. Drew Westen, a psychologist at Emory and lead author of the study, to be presented Saturday at meetings of the Society for Personality and Social Psychology in Palm Springs, Calif.

The results are the latest from brain imaging studies that provide a neural explanation for internal states, like infatuation or ambivalence, and a graphic trace of the brain's activity.

In 2004, the researchers recruited 30 adult men who described themselves as committed Republicans or Democrats. The men, half of them supporters of President Bush and the other half backers of Senator John Kerry, earned $50 to sit in an M.R.I. machine and consider several statements in quick succession.

The first was a quote attributed to one of the two candidates: either a remark by Mr. Bush in support of Kenneth L. Lay, the former Enron chief, before he was indicted, or a statement by Mr. Kerry that Social Security should be overhauled. Moments later, the participants read a remark that showed the candidate reversing his position. The quotes were doctored for maximum effect but presented as factual.

The Republicans in the study judged Mr. Kerry as harshly as the Democrats judged Mr. Bush. But each group let its own candidate off the hook.

After the participants read the contradictory comment, the researchers measured increased activity in several areas of the brain. They included a region involved in regulating negative emotions and another called the cingulate, which activates when the brain makes judgments about forgiveness, among other things. Also, a spike appeared in several areas known to be active when people feel relieved or rewarded. The "cold reasoning" regions of the cortex were relatively quiet.

It's all about keeping activity flaring in the pleasure center, baby!

As a follow-up study, researchers will look at the areas of the brain affected most strongly by snark.