Editor's note: This is an excerpt from Chris Mooney’s book The Republican Brain: The Science of Why They Deny Science and Reality.

In June of 2011, Jon Stewart went on air with Fox News’ Chris Wallace and started a major media controversy over the channel’s misinforming of its viewers. “Who are the most consistently misinformed media viewers?” Stewart asked Wallace. “The most consistently misinformed? Fox, Fox viewers, consistently, every poll.”

Stewart’s statement was factually accurate, as we’ll see. The next day, however, the fact-checking site PolitiFact weighed in and rated it “false.”In claiming to check Stewart’s “facts,” PolitiFact ironically committed a serious error—and later, doubly ironically, failed to correct it. How’s that for the power of fact checking?

There probably is a small group of media consumers out there somewhere in the world who are more misinformed, overall, than Fox News viewers. But if you only consider mainstream U.S. television news outlets with major audiences (e.g., numbering in the millions), it really is true that Fox viewers are the most misled based on all the available evidence—especially in areas of political controversy. This will come as little surprise to liberals, perhaps, but the evidence for it—evidence in Stewart’s favor—is pretty overwhelming.

My goal here is to explore the underlying causes for this “Fox News effect”—explaining how this station has brought about a hurricane-like intensification of factual error, misinformation and unsupportable but ideologically charged beliefs on the conservative side of the aisle. First, though, let’s begin by surveying the evidence about how misinformed Fox viewers actually are.

Based upon my research, I have located seven separate studies that support Stewart’s claim about Fox, and none that undermine it. Six of these studies were available at the time that PolitFact took on Stewart; one of them is newer.

The studies all take a similar form: These are public opinion surveys that ask citizens about their beliefs on factual but contested issues, and also about their media habits. Inevitably, some significant percentage of citizens are found to be misinformed about the facts, and in a politicized way—but not only that. The surveys also find that those who watch Fox are more likely to be misinformed, their views of reality skewed in a right-wing direction. In some cases, the studies even show that watching more Fox makes the misinformation problem worse.

So with that, here are the studies.

Iraq War

In 2003, a surveyby the Program on International Policy Attitudes (PIPA) at the University of Maryland found widespread public misperceptions about the Iraq war. For instance, many Americans believed the U.S. had evidence that Saddam Hussein’s Iraq had been collaborating in some way with Al Qaeda, or was involved in the 9-11 attacks; many also believed that the much touted “weapons of mass destruction” had been found in the country after the U.S. invasion, when they hadn’t. But not everyone was equally misinformed: “The extent of Americans’ misperceptions vary significantly depending on their source of news,” PIPA reported. “Those who receive most of their news from Fox News are more likely than average to have misperceptions.” For instance, 80 percent of Fox viewers held at least one of three Iraq-related misperceptions, more than a variety of other types of news consumers, and especially NPR and PBS users. Most strikingly, Fox watchers who paid more attention to the channel were more likely to be misled.

Global Warming

At least two studies have documented that Fox News viewers are more misinformed about this subject.

In a late 2010 survey, Stanford University political scientist Jon Krosnick and visiting scholar Bo MacInnis found that “more exposure to Fox News was associated with more rejection of many mainstream scientists’ claims about global warming, with less trust in scientists, and with more belief that ameliorating global warming would hurt the U.S. economy.” Frequent Fox viewers were less likely to say the Earth’s temperature has been rising and less likely to attribute this temperature increase to human activities. In fact, there was a 25 percentage point gap between the most frequent Fox News watchers (60%) and those who watch no Fox News (85%) in whether they think global warming is “caused mostly by things people do or about equally by things people do and natural causes.”

In a much more comprehensive study released in late 2011 (too late for Stewart or for PolitiFact), American University communications scholar Lauren Feldman and her colleagues reported on their analysis of a 2008 national survey, which found that “Fox News viewing manifests a significant, negative association with global warming acceptance.” Viewers of the station were less likely to agree that “most scientists think global warming is happening” and less likely to think global warming is mostly caused by human activities, among other measures.

Health Care

In 2009, an NBC survey found “rampant misinformation” about the healthcare reform bill before Congress — derided on the right as “Obamacare.”It also found that Fox News viewers were much more likely to believe this misinformation than average members of the general public. “72% of self-identified Fox News viewers believe the healthcare plan will give coverage to illegal immigrants, 79% of them say it will lead to a government takeover, 69% think that it will use taxpayer dollars to pay for abortions, and 75% believe that it will allow the government to make decisions about when to stop providing care for the elderly,” the survey found.

By contrast, among CNN and MSNBC viewers, only 41 percent believed the illegal immigrant falsehood, 39 percent believed in the threat of a “government takeover” of healthcare (40 percentage points less), 40 percent believed the falsehood about abortion, and 30 percent believed the falsehood about “death panels” (a 45 percent difference!).

In early 2011, the Kaiser Family Foundation released another survey on public misperceptions about healthcare reform. The poll asked 10 questions about the newly passed healthcare law and compared the “high scorers”—those that answered 7 or more correct—based on their media habits. The result was that “higher shares of those who report CNN (35 percent) or MSNBC (39 percent) as their primary news source [got] 7 or more right, compared to those that report mainly watching Fox News (25 percent).”

"Ground Zero Mosque”

In late 2010, two scholars at the Ohio State University studied public misperceptions about the so-called “Ground Zero Mosque”—and in particular, the prevalence of a series of rumors depicting those seeking to build this Islamic community center and mosque as terrorist sympathizers, anti-American, and so on. All of these rumors had, of course, been dutifully debunked by fact-checking organizations. The result? “People who use Fox News believe more of the rumors we asked about and they believe them more strongly than those who do not.”

The 2010 Election

In late 2010, the Program on International Policy Attitudes (PIPA) once again singled out Fox in a survey about misinformation during the 2010 election. Out of 11 false claims studied in the survey, PIPA found that “almost daily” Fox News viewers were “significantly more likely than those who never watched it” to believe 9 of them, including the misperceptions that “most scientists do not agree that climate change is occurring” (they do), that “it is not clear that President Obama was born in the United States” (he was), that “most economists estimate the stimulus caused job losses” (it either saved or created several million), that “most economists have estimated the healthcare law will worsen the deficit” (they have not), and so on.

It is important to note that in this study—by far the most critiqued of the bunch—the examples of misinformation studied were all closely related to prominent issues in the 2010 midterm election, and indeed, were selected precisely because they involved issues that voters said were of greatest importance to them, like healthcare and the economy. That was the main criterion for inclusion, explains PIPA senior research scholar Clay Ramsay. “People said, here’s how I would rank that as an influence on my vote,” says Ramsay, “so everything tested is at least a 5 on a zero-to-10 scale.”

Politifact Swings and Misses

In attempting to fact-check Jon Stewart on the subject of Fox News and misinformation, PolitiFact simply appeared out of its depth. The author of the article in question, Louis Jacobson, only cited two of the studies above–“Iraq War” and “2010 Election”—though six out of seven were available at the time he was writing. And then he suggested that the “2010 Election” study should “carry less weight” due to various methodological objections.

Meanwhile, Jacobson dug up three separate studies that we can dismiss as irrelevant. That’s because these studies did not concern misinformation, but rather, how informed news viewers are about basic political facts like the following: “who the vice president is, who the president of Russia is, whether the Chief Justice is conservative, which party controls the U.S. House of Representatives and whether the U.S. has a trade deficit.”

A long list of public opinion studies have shown that too few Americans know the answers to such basic questions. That’s lamentable, but also off point at the moment. These are not politically contested issues, nor are they skewed by an active misinformation campaign. As a result, on such issues many Americans may be ill-informed but liberals and conservatives are nevertheless able to agree.

Jon Stewart was clearly talking about political misinformation. He used the word “misinformed.” And for good reason: Misinformation is by far the bigger torpedo to our national conversation, and to any hope of a functional politics. “It’s one thing to be not informed,” explains David Barker, a political scientist at the University of Pittsburgh who has studied conservative talk-radio listeners and Fox viewers. “It’s another thing to be misinformed, where you’re confident in your incorrectness. That’s the thing that’s really more problematic, democratically speaking—because if you’re confidently wrong, you’re influencing people.”

Thus PolitiFact’s approach was itself deeply uninformed, and underscores just how poorly our mainstream political discourse deals with the problem of systematic right wing misinformation.

Fox and the Republican Brain

The evidence is clear, then—the Politifact-Stewart flap notwithstanding, Fox viewers are the most misinformed. But then comes the truly interesting and important question: Why is that the case?

To answer it, we’ll first need to travel back to the 1950s, and the pioneering work of the Stanford psychologist and cult infiltrator, Leon Festinger.

In his 1957 book A Theory of Cognitive Dissonance, Festinger built on his famous study of a doomsday cult called the Seekers, and other research, to lay out many ramifications of his core idea about why human beings contort the evidence to fit their beliefs, rather than conforming those beliefs to the evidence. That included a prediction about how those who are highly committed to a belief or view should go about seeking information that touches on that powerful conviction.

Festinger suggested that once we’ve settled on a core belief, this ought to shape how we gather information. More specifically, we are likely to try to avoid encountering claims and information that challenge that belief, because these will create cognitive dissonance. Instead, we should go looking for information that affirms the belief. The technical (and less than ideal) term for this phenomenon is “selective exposure”: what it means is that we selectively choose to be exposed to information that is congenial to our beliefs, and to avoid “inconvenient truths” that are uncongenial to them.

If Festinger’s ideas about “selective exposure” are correct, then the problem with Fox News may not solely be that it is actively causing its viewers to be misinformed. It’s very possible that Fox could be imparting misinformation even as politically conservative viewers are also seeking the station out—highly open to it and already convinced about many falsehoods that dovetail with their beliefs. Thus, they would come into the encounter with Fox not only misinformed and predisposed to become more so, but inclined to be very confident about their incorrect beliefs and to impart them to others. In this account, political misinformation on the right would be driven by a kind of feedback loop, with both Fox and its viewers making the problem worse.

Psychologists and political scientists have extensively studied selective exposure, and within the research literature, the findings are often described as mixed. But that’s not quite right. In truth, some early studies seeking to confirm Festinger’s speculation had problems with their designs and often failed—and as a result, explains University of Alabama psychologist William Hart, the field of selective exposure research “stagnated” for several decades. But it has since undergone a dramatic revival—driven, not surprisingly, by the modern explosion of media choices and growing political polarization in the U.S. And thanks to a new wave of better-designed and more rigorous studies, the concept has become well established.

“Selective exposure is the clearest way to look at how people create their own realities, based upon their views of the world,” says Hart. “Everybody knows this happens.”

Indeed, by 2009, Hart and a team of researchers were able to perform a meta-analysis—a statistically rigorous overview of published studies on selective exposure—that pooled together 67 relevant studies, encompassing almost 8,000 individuals. As a result, he found that people overall were nearly twice as likely to consume ideologically congenial information as to consume ideologically inconvenient information—and in certain circumstances, they were even more likely than that.

When are people most likely to seek out self-affirming information? Hart found that they’re most vulnerable to selective exposure if they have defensive goals—for instance, being highly committed to a preexisting view, and especially a view that is tied to a person’s core values. Another defensive motivation identified in Hart’s study was closed-mindedness, which makes a great deal of sense. It is probably part of the definition of being closed-minded, or dogmatic, that you prefer to consume information that agrees with what you already believe.

So who’s closed-minded? Multiple studies have shown that political conservatives—e.g., Fox viewers–tend to have a higher need for closure. Indeed, this includes a group called right-wing authoritarians, who are increasingly prevalent in the Republican Party. This suggests they should also be more likely to select themselves into belief-affirming information streams, like Fox News or right-wing talk radio or the Drudge Report. Indeed, a number of research results support this idea.

In a study of selective exposure during the 2000 election, for instance, Stanford University’s Shanto Iyengar and his colleagues mailed a multimedia informational CD about the two candidates—Bush and Gore—to 600 registered voters and then tracked its use by a sample of 220 of them. As a result, they found that Bush partisans chose to consume more information about Bush than about Gore—but Democrats and liberals didn’t show the same bias toward their own candidate.

Selective exposure has also been directly tested several times in authoritarians. In one case, researchers at Stony Brook University primed more and less authoritarian subjects with thoughts of their own mortality. Afterwards, the authoritarians showed a much stronger preference than non-authoritarians for reading an article that supported their existing view on the death penalty, rather than an article presenting the opposing view or a “balanced” take on the issue. As the authors concluded: “highly authoritarian individuals, when threatened, attempt to reduce anxiety by selectively exposing themselves to attitude-validating information, which leads to ‘stronger’ opinions that are more resistant to attitude change.”

The psychologist Robert Altemeyer of the University of Manitoba has also documented an above average amount of selective exposure in right wing authoritarians. In one case, he gave students a fake self-esteem test, in which they randomly received either above average or below average scores. Then, everyone—the receivers of both low and high scores—was given the opportunity to say whether he or she would like to read a summary of why the test was valid. The result was striking: Students who scored low on authoritarianism wanted to learn about the validity of the test regardless of how they did on it. There was virtually no difference between high and low scorers. But among the authoritarian students, there was a big gap: 73 percent of those who got high self-esteem scores wanted to read about the test’s validity, while only 47 percent of those who got low self-esteem scores did.

Authoritarians, Altemeyer concludes, “maintain their beliefs against challenges by limiting their experiences, and surrounding themselves with sources of information that will tell them they are right.”

The evidence on selective exposure, as well as the clear links between closed-mindedness and authoritarianism, gives good grounds for believing that this phenomenon should be more common and more powerful on the political right. Lest we leap to the conclusion that Fox News is actively misinforming its viewers most of the time—rather than enabling them through its very existence—that’s something to bear in mind.

Disinformation Passing as “News”

None of which is to suggest that Fox isn’t also guilty of actively misinforming viewers. It certainly is.

The litany of misleading Fox segments and snippets is quite extensive—especially on global warming, where it seems that every winter snowstorm is an excuse for more doubt-mongering. No less than Fox’s Washington managing editor Bill Sammon was found to have written, in a 2009 internal staff email exposed by MediaMatters, that the network’s journalists should:

. . . refrain from asserting that the planet has warmed (or cooled) in any given period without IMMEDIATELY pointing out that such theories are based upon data that critics have called into question. It is not our place as journalists to assert such notions as facts, especially as this debate intensifies.

And global warming is hardly the only issue where Fox actively misinforms its viewers. The polling data here, from the Project on International Policy Attitudes (PIPA) are very telling.

PIPA’s study of misinformation in the 2010 election didn’t just show that Fox News viewers were more misinformed than viewers of other channels. It also showed that watching more Fox made believing in nine separate political misperceptions more likely. And that was a unique effect, unlike any observed with the other news channels that were studied. “With all of the other media outlets, the more exposed you were, the less likely you were to have misinformation,” explains PIPA’s director, political psychologist Steven Kull. “While with Fox, the more exposure you had, in most cases, the more misinformation you had. And that is really, in a way, the most powerful factor, because it strongly suggests they were actually getting the information from Fox.”

Indeed, this effect was even present in non-Republicans–another indicator that Fox is probably its cause. As Kull explains, “even if you’re a liberal Democrat, you are affected by the station.” If you watched Fox, you were more likely to believe the nine falsehoods, regardless of your political party affiliation.

In summary, then, the “science” of Fox News clearly shows that its viewers are more misinformed than the viewers of other stations, and are indeed this way for ideological reasons. But these are not necessarily the reasons that liberals may assume. Instead, the Fox “effect” probably occurs both because the station churns out falsehoods that conservatives readily accept—falsehoods that may even seem convincing to some liberals on occasion—but also because conservatives are overwhelmingly inclined to choose to watch Fox to begin with.

At the same time, it’s important to note that they’re also disinclined to watch anything else. Fox keeps constantly in their minds the idea that the rest of the media are “biased” against them, and conservatives duly respond by saying other media aren’t worth watching—it’s just a pack of lies. According to Public Policy Polling’s annual TV News Trust Poll (the 2011 run), 72 percent of conservatives say they trust Fox News, but they also say they strongly distrust NBC, ABC, CBS and CNN. Liberals and moderates, in contrast, trust all of these outlets more than they distrust them (though they distrust Fox). This, too, suggests conservative selective exposure.

And there is an even more telling study of “Fox-only” behavior among conservatives, from Stanford’s Shanto Iyengar and Kyu Hahn of Yonsei University, in Seoul, South Korea. They conducted a classic left-right selective exposure study, giving members of different ideological groups the chance to choose stories from a news stream that provided them with a headline and a news source logo—Fox, CNN, NPR, and the BBC—but nothing else. The experiment was manipulated so that the same headline and story was randomly attributed to different news sources. The result was that Democrats and liberals were definitely less inclined to choose Fox than other sources, but spread their interest across the other outlets when it came to news. But Republicans and conservatives overwhelmingly chose Fox for hard news and even for soft news, and ignored other sources. “The probability that a Republican would select a CNN or NPR report was around 10%,” wrote the authors.

In other words Fox News is both deceiver and enabler simultaneously. First, its existence creates the opportunity for conservatives to exercise their biases, by selecting into the Fox information stream, and also by imbibing Fox-style arguments and claims that can then fuel biased reasoning about politics, science, and whatever else comes up.

But at the same time, it’s also likely that conservatives, tending to be more closed-minded and more authoritarian, have a stronger emotional need for an outlet like Fox, where they can find affirmation and escape from the belief challenges constantly presented by the “liberal media.” Their psychological need for something affirmative is probably stronger than what’s encountered on the opposite side of the aisle—as is their revulsion towards allegedly liberal (but really centrist) media outlets.

And thus we find, at the root of our political dysfunction, a classic nurture-nature mÃ©lange. The penchant for selective exposure is rooted in our psychology and our brains. Closed-mindedness and authoritarianism—running stronger in some of us than in others—likely are as well.

But nevertheless, it took the emergence of a station like Fox News before these tendencies could be fully activated—polarizing America not only over politics, but over reality itself.