By JOSHUA FREEDMAN
http://www.nytimes.com/2005/01/18/opinion/18freedman.html?oref=login&th

Los Angeles — PRESIDENT BUSH begins his second term this week as the leader of a nation that appears to be sharply divided. Since the election, there's been endless discussion about the growing gap between "red" and "blue" America. When former President Bill Clinton said a few months ago that he was probably the only person in America who liked both Mr. Bush and Senator John Kerry, it seemed it might be true.

Yet, surprisingly, recent neuroscience research suggests that Democrats and Republicans are not nearly as far apart as they seem. In fact, there is empirical evidence that even the fiercest partisans may instinctively like both Mr. Bush and Mr. Kerry, although they struggle against this collaborative impulse.

During the eight months before the election, I was part of a group of political professionals and scientists from the University of California, Los Angeles, who used functional magnetic resonance imaging, or f.M.R.I., to scan the brains of 10 Republicans and 10 Democrats, producing images like those seen above. We measured brain activity while subjects looked at political advertisements and at images of the presidential candidates.

The news media have focused on our finding that the amygdala, a part of the brain that responds to danger, was more heightened in Democrats when viewing scenes of 9/11 than in Republicans. This might seem to indicate fundamental differences, but other aspects of our results suggest striking commonalities.

These patterns of brain activity, made visible on the f.M.R.I.'s, suggest that both Bush and Kerry voters were mentally battling their attraction to the other side. Bush voters wanted to follow Mr. Kerry; Kerry voters found appeal in Mr. Bush. Both groups fought this instinct by arguing to themselves that their impulses were wrong. By recalling flaws associated with the opposition, the voters displaced attraction with dislike. Because the process happened nearly instantaneously, only the final sense of dismay reached full awareness.

Simplifying the neurophysiology somewhat, one can regard the process of reaching an opinion or making a choice as a collaboration between two regions of the brain - the limbic area, which feels emotions, and the prefrontal cortex, which controls the processing of ideas and information. The two areas work in tandem: thoughts provoke feelings, and in turn, the intensity of these feelings determines how the thoughts are valued. In reacting to pictures of the opposing candidate, the voters we tested countered the feelings of connection with even stronger hostile emotions, which they induced by calling up negative images and ideas.