Is There a "Liberal Media Bias"?

Glenn Greenwald, in a predictably grating bit of rhetorical overkill, says no:

The very notion of the "Liberal Media" is one of the most inane myths in American politics -- something spat out and repeated in the lowest right-wing sewers for so long that it has become conventional wisdom. ... It's literally hard to imagine a claim that ought to be more discredited in general than the notion of the "liberal media" and its "anti-Republican bias."

The issue of media bias has been debated and studied for decades, and both sides can cite academic research that supports their argument. But the process of defining and measuring "media bias" is so inherently subjective that I don't think it's possible to conduct an objective empirical study.

I tend to think there is a "liberal media bias," based on two facts. First, surveys have consistently shown that journalists are far more likely to be Democrats than Republicans. For example, a 1999 survey by the American Society of Newspaper Editors found:

At the bigger papers, 61 percent of newsroom respondents described themselves as Democrats (or leaning toward Democrat) and only 10 percent as Republicans (or leaning toward Republican). At small papers, the number of Democrats (and leaners) drops to 48 percent and Republicans (and leaners) rises to 21 percent.

Second, neurological studies have shown that people's feelings toward a political party dramatically affect the way their brains interpret political news. In his book The Political Brain, Drew Weston described a great study he and two colleagues conducted during the 2004 election. Westen and his colleagues studied the brains of 15 self-identified Democrats and 15 self-identified Republicans as they were presented with a series of slides that showed undeniably inconsistent statements by John Kerry. The partisans were asked to consider whether Kerry's two statements were inconsistent, and were then asked to rate the extent to which Kerry's statements were contradictory, from 1 (strongly disagree) to 4 (strongly agree). They then repeated the process with undeniably inconsistent statements by George W. Bush, and again with inconsistent statements by politically neutral males. Here's how Westen described the results:

They had no trouble seeing the contradictions for the opposition candidate, rating his inconsistencies close to 4 on the four-point rating scale. For their own candidate, however, ratings averaged closer to 2, indicating minimal contradiction. Democrats responded to Kerry as Republicans responded to Bush. And as predicted, Democrats and Republicans showed no differences in their response to contradictions for the politically neutral figures.
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The results showed that when partisans face threatening information, not only are they likely to "reason" to emotionally biased conclusions, but we can trace their neutral footprints as they do it.

When confronted with potentially troubling political information, a network of neurons becomes active that produces distress. ... The brain registers the conflict between the data and desire and begins to search for ways to turn off the spigot of unpleasant emotion. We know that the brain largely succeeded in this effort, as partisans mostly denied that they had perceived any conflict between their candidate's words and deeds.

Not only did the brain manage to shut down distress through faulty reasoning, but it did so quickly -- as best we could tell, usually before subjects even made it to the third slide [which asked them to consider whether the statements were inconsistent]. The neural circuits charged with regulation of emotional states seemed to recruit beliefs that eliminated the distress and conflict partisans had experienced when they confronted unpleasant realities. And this all seemed to happen with little involvement of the circuits normally involved in reasoning.

But the political brain also did something we didn't predict. Once partisans had found a way to reason to false conclusions, not only did neural circuits involved in negative emotions turn off, but circuits involved in positive emotions turned on. The partisan brain didn't seem satisfied in just feeling better. It worked overtime to feel good, activating reward circuits that give partisans a jolt of positive reinforcement for their biased reasoning.

This is basically the root of the well-known "confirmation bias."

So given that (1) journalists are overwhelmingly Democrats, and (2) party affiliation dramatically affects the way our brains interpret political news, is it really possible that there isn't a liberal media bias?

No empirical study of newspaper stories or talking heads on TV is ever going to be able to objectively determine whether there's a liberal media bias, because what people think constitutes "liberal bias" depends on their party affiliation also. I don't perceive a liberal media bias, but then again, I'm a Democrat, so my brain would presumably interpret political news the same way a biased liberal media would.

But if we know that the inputs are heavily biased, it's very likely that the output is biased as well.