For example, Berinsky (2012) found that among Republicans, corrections of the death-panel myth were effective primarily when they were issued by a Republican politician. However, judgments of a source’s credibility are themselves a function of beliefs: If you believe a statement, you judge its source to be more credible (Fragale & Heath, 2004). This interaction between belief and credibility judgments can lead to an epistemic circularity, whereby no opposing information is ever judged sufficiently credible to overturn dearly held prior knowledge. For example, Munro (2010) has shown that exposure to belief-threatening scientific evidence can lead people to discount the scientific method itself: People would rather believe that an issue cannot be resolved scientifically, thus discounting the evidence, than accept scientific evidence in opposition to their beliefs.

Amusingly, after I had read this bit, I realized that I had been trusting this article and its authors more because the claims it made sounded credible. That's a pretty vicious cycle: if somebody says things that support your beliefs, you judge them to be more credible, and then your beliefs get stronger because credible sources support them... maybe I should try to correct for that by trusting this article less. :)