A friend sent me two wonderful articles on the neuroscience behind how humans make decisions. The first is "My Candidate, Myself" by Robert Burton about the fact that people make their decisions based on the feeling of being right, even when it conflicts with rational evidence. Also, those who score the lowest on tests, the most incompetent individuals, tend to most overestimate their own abilities, while those who performed best were closer to being correct. He applies it to politics in showing that a person who has made up his or her mind on a political candidate usually won't change regardless of being shown facts that are not to the advantage of that candidate. Moreover, he would like to test the candidates with questions that would show how they make decisions.
The second article is an excerpt from a book, On Being Certain, also by Robert Burton. He talks again about the neurobiology of "knowing" something. In this article he argues that we should frame even scientific statements in terms of "I believe" rather than "I know", thinking that this would increase the impact on those who "know" to the contrary. I'm not sure I agree, but it is certainly interesting.