Their convictions grow. It's the basic mechanism of cognitive dissonance: your mind is presented with conflicting signals, one of which is comfortable, one of which is uncomfortable. We resolve this intellectually by clinging more strongly to the signal we appreciate and assigning higher value to the aspects of the idea that haven't been disproven.

Case in point: vaccination prejudice. This starts (in the modern era, anyway - Raggedy Ann was designed by a guy who lost his daughter to the mumps vaccine, if I recall) with Wakefield's autism link.

The autism link is questioned pretty quickly. So Bobby Kennedy publishes an article in Salon linking thimerosal to autism.

The article is resoundingly dismantled and pulled by Salon. So now we're going for "additives" in vaccines.

"Additives" in vaccines are empirically proven to not bloody matter. So now we're assailing all of germ theory.

And all along the way, some people were pruned out of the anti-vax camp by logic. Those that weren't, though, were driven further and further into teh crazeh.

SEE ALSO: climate change "skeptics."

Best book I've read on the subject is Drive by Dan Pink.