I wrote another post at the Princeton University Press blog. This summarizes the theories of rational ignorance and rational irrationality, while also explaining some findings in political psychology.

http://press.princeton.edu/blog/2012/09/17/jason-brennan-on-why-were-dumb-at-politics/

Excerpt:

Few of us form our original political beliefs after first weighing the evidence. Instead, when we first start thinking about politics, we come to the table with groundless political beliefs. We begin with bents to believe some things and disbelieve others. For no good reason, we start off left or right, libertarian or authoritarian, market-friendly or anti-market, and so on.

Our political beliefs are at least moderately hereditable. Our genes dispose us to vote one way rather than another. Early childhood experiences also push you one way rather than another. By sheer accident, you might come to associate the Democrats with compassion or the Republicans with responsibility. For you, for the rest of your life, the word “Democrat” will automatically conjure up positive emotions. For the rest of your life, you’ll have a bent—based on no evidence at all—to vote one way rather than another.

When people first start thinking about politics, they come to the table with (often strongly held) pre-existing beliefs. That’s already a worry. Yet if we were really good at assessing evidence and changing our beliefs in light of evidence, then our non-rational bents would not be so bad. Sure, we’d start with groundless, baseless beliefs, but we’d end up with well-grounded beliefs. Young people would start as hacks, but end up as sages.

Alas, we are bad at assessing evidence. Most of stay hacks.