Why can both liberals think the media is biased toward conservatives and conservatives think the media is biased against them? (Not to mention, why do libertarians like me think the media is biased toward government action?)

Here’s a rough draft of a theory. John Zaller’s The Nature and Origins of Mass Opinion makes a case for what he calls the “receive-accept-sample” (RAS) model of opinionation. In simple terms, people receive information (which may or may not be biased; it can be purely factual, or it can be partisan or distorted in some way) from a variety of sources, such as the mass media, friends, family, colleagues, etc. This information is then either accepted or rejected through a process of perceptual screening. Finally, when people are called upon to give their opinion on a particular issue, they sample from the information they have available pertaining to that issue (in Zaller’s terms, the relevant considerations).

Now, if we focus on the accept part of the RAS model, we find something interesting. People who are more politically sophisticated generally only accept the information that is consistent with their preexisting beliefs, while less sophisticated people have less developed screening mechanisms (since they care less about consistency or balance). People who complain about bias are, largely, the politically sophisticated (those who look down on Rush Limbaugh or Bill O’Reilly listeners may find this hard to accept, but compared to the average American I suspect those listeners are more politically sophisticated; they may have political beliefs that seem reactionary, but they generally know a lot more about politics and how it works than the average citizen). This probably isn’t a coincidence.

My theory is that citizens are more conscious of rejection than they are of acceptance. People who encounter information consistent with their beliefs will simply accept it and move on, while people who encounter information that is inconsistent will be more aware of that inconsistency. Thus, people who encounter more inconsistency when they encounter information from a particular source will find it to be more biased than those who encounter less inconsistency. And, they will perceive that bias as being in the direction opposite to their preexisting belief system—because, relative to them, the bias is in that direction.

Does that mean (if this theory is correct—I suspect it is, but then again, that’s because it’s my theory) that bias doesn’t exist? No. But it does mean that liberals like Eric Alterman and conservatives like Ann Coulter will only perceive bias in opposition to their own belief system.

Conceivably, one could pick a “belief system axis” and measure the bias of various information sources relative to the origin of that axis. To test this, you’d need to have a number of raters from various positions within that belief system axis (which you could locate using standard measures of ideological belief) and then have them give some measure of the bias of the information sources. Then you could produce an “objective” map of the bias of the sources using multidimensional scaling (which, hopefully, would be fairly easy to interpret).