The most recent demonstration came in the matter of election polls. Coming into the recent election, state-level polling clearly pointed to an Obama victory — yet more or less the whole Republican Party refused to acknowledge this reality. Instead, pundits and politicians alike fiercely denied the numbers and personally attacked anyone pointing out the obvious; the demonizing of The Times’s Nate Silver, in particular, was remarkable to behold.

What accounts for this pattern of denial? Earlier this year, the science writer Chris Mooney published “The Republican Brain,” which was not, as you might think, a partisan screed. It was, instead, a survey of the now-extensive research linking political views to personality types. As Mr. Mooney showed, modern American conservatism is highly correlated with authoritarian inclinations — and authoritarians are strongly inclined to reject any evidence contradicting their prior beliefs. Today’s Republicans cocoon themselves in an alternate reality defined by Fox News, Rush Limbaugh and The Wall Street Journal’s editorial page, and only on rare occasions — like on election night — encounter any hint that what they believe might not be true.

And, no, it’s not symmetric. Liberals, being human, often give in to wishful thinking — but not in the same systematic, all-encompassing way.