I'm Going to Change Your Mind About Politics Through Facebook

3. "Confirmation Bias":

THE MISCONCEPTION: Your opinions are the result of years of rational, objective analysis.

THE TRUTH: Your opinions are the result of years of paying attention to information that confirmed what you believed, while ignoring information that challenged your preconceived notions.

You might remember this concept from my post about You Are Not So Smart, a book about all the ways we delude ourselves and "think" with our irrational emotions instead of the rational logic we believe.  More evidence, in a political context:

How Facts Backfire
Researchers Discover a Surprising Threat to Democracy: Our Brains

These findings open a long-running argument about the political ignorance of American citizens to broader questions about the interplay between the nature of human intelligence and our democratic ideals. Most of us like to believe that our opinions have been formed over time by careful, rational consideration of facts and ideas, and that the decisions based on those opinions, therefore, have the ring of soundness and intelligence. In reality, we often base our opinions on our beliefs, which can have an uneasy relationship with facts. And rather than facts driving beliefs, our beliefs can dictate the facts we chose to accept. They can cause us to twist facts so they fit better with our preconceived notions. Worst of all, they can lead us to uncritically accept bad information just because it reinforces our beliefs. This reinforcement makes us more confident we’re right, and even less likely to listen to any new information. And then we vote. . . .

it appears that misinformed people often have some of the strongest political opinions. . . .

A 2006 study by Charles Taber and Milton Lodge at Stony Brook University showed that politically sophisticated thinkers were even less open to new information than less sophisticated types. These people may be factually right about 90 percent of things, but their confidence makes it nearly impossible to correct the 10 percent on which they’re totally wrong. Taber and Lodge found this alarming, because engaged, sophisticated thinkers are “the very folks on whom democratic theory relies most heavily.” . . .