From The Nieman Lab, a striking bit of analysis about people who watch Fox News or MSNBC all day:
When people were prompted to think about Republicans and Democrats, they perceived more media bias against their views, as indicated by the steep dashed line. When they were instructed to think about America vs. the world, they perceived slightly less bias then the neutral condition, as indicated by the shallow dotted line. Our perception of bias changes depending on the self-identity we currently have in mind.
This self-categorization explanation also predicts that people who are more partisan perceive greater bias, even when the news is in their favor. In Reid’s second experiment, people read an article about polling numbers for the 2008 presidential primaries, containing language like “among Republicans, former New York mayor Rudy Giuliani maintained a 14-point lead over Arizona Sen. John McCain for the Republican presidential nomination,” and similar statements about the Democratic candidates. This time, the source of the information was manipulated: One group saw the poll attributed to the “Economic Policy Institute, a Democrat think tank and polling agency,” while the other was told it came from the “American Enterprise Institute, a Republican think tank and polling agency.”
In this purely factual scenario — dry-as-toast poll numbers, no opinions, no editorializing — respondents still had completely different reactions depending on the source. As you might expect, people who believed that the poll numbers came from the American Enterprise Institute thought that the story was biased towards Giuliani (and vice versa), confirming the hostile media effect. But the perception of favoritism increased not according to whether the reader personally identified as Republican or Democratic, but on how strong this identification was. The implication is that if you feel strongly about your group, you’re likely to see all news as more biased — even when the bias favors you.
Reid’s final experiment tested perceptions of overt attacks. He used a scathing review of Michael Moore’s Fahrenheit 911, originally published on Slate, which begins:
One of the many problems with the American left, and indeed of the American left, has been its image and self-image as something rather too solemn, mirthless, herbivorous, dull, monochrome, righteous, and boring.
The copy given to subjects (falsely) claimed the author was a member of either a Democrat or a Republican think tank. (In reality, the author was the late Christopher Hitchens.) As you might expect, people who identified as Republicans saw the review as more neutral, regardless of who they thought wrote it. The strange thing is that strong Democrats actually saw the review as slightly in favor of Democrats when they believed it was written by a Democrat! We interpret criticism completely differently depending on how we see the relationship between ourselves and the author.