A more quantitative look at this same thing. Basically saying that people pick what interests them. This is pretty technical, but by some pretty smart people:

http://home.uchicago.edu/~jmshapir/bias.pdf

And, my own experiment with media influence. This counteracts both the master link and the link above. My short experiment has correlation to show that the media has more influence on public perception. Though, this was just a proof-of-concept and not a vetted research project:

http://publicthoughts.com/media-affects-opinion/