researchers have studied both Democrat and Republican partisans using brain scans and other techniques

When we contemplate contradictions in the rhetoric of the opposition party’s candidate, the rational centers of our brains are active, but contradictions from our own party’s candidate set off a different reaction: the emotional centers light up and levels of feel-good dopamine surge.

With our rational faculties muted, sometimes the unwelcome evidence doesn’t even register, and sometimes we use marvelous logic to get around the facts.

In one study, Republicans who blamed Saddam Hussein for the attacks of Sept. 11, 2001, were presented with strong counterevidence, including a statement from President George W. Bush absolving Hussein. But most of the people in the study went on blaming Hussein anyway, as the researchers report in the current issue of Sociological Inquiry.

Some of the people ignored or rejected the counterevidence; some “counterargued” that Hussein was evil enough to do it; some flatly said they were entitled to counterfactual opinions. And some came up with an especially creative form of motivated reasoning that the psychologists labeled “inferred justification”: because the United States went to war against Hussein, the reasoning went, it must therefore have been provoked by his attack on Sept. 11.

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