Is man-made global warming happening? Can nuclear waste be stored safely? Do concealed handguns reduce violence? Think about those questions for a minute. Then think about your thinking: Why do you hold those particular views on these controversial issues? And do scientific experts agree with you?

The Yale Cultural Cognition Project has been probing the question of cultural polarization over scientific risk issues for a number of years. The project's latest working paper, "Cultural Cognition of Scientific Consensus," analyzes the question: "Why do members of the public disagree—sharply and persistently—about facts on which expert scientists largely agree?" As examples of strong expert scientific consensus, researchers led by Yale University law professor Daniel Kahan selected three recent National Academy of Sciences (NAS) reports dealing with climate change, nuclear waste, and gun possession.

To get at what Americans think about each of these three issues, the Yale researchers conducted a poll of 1,500 Americans in July 2009. But first the pollsters asked questions designed to elicit each respondent's cultural worldview. The project uses a modified version of a typology devised in the 1980s by brilliant University of California-Berkeley sociologist Aaron Wildavsky which divides Americans into four cultural groups: Individualists, Communitarians, Hierarchicalists, and Egalitarians.

Hierarchicalists prefer a social order where people have clearly defined roles based on stable characteristics such as class, race, or gender. Egalitarians want to reduce racial, gender, and income inequalities. Individualists expect people to succeed or fail on their own, while Communitarians believe that society is obligated to take care of everyone. Generally speaking, Individualists tend to dismiss claims of environmental risks because they fear such claims will be used to fetter markets and other arenas of individual achievement. Hierarchicalists tend to see claims of environmental risk as a subversive tactic aiming to undermine a stable social order. In contrast, Egalitarians and Communitarians dislike markets and industry for creating disparities in wealth and power. In fact, they readily believe that such disparities generate environmental risks that must be regulated.

Once poll participants were sorted into cultural value groups, they were asked a series of questions about what experts think about global warming, nuclear waste disposal, and the risks of concealed carry gun laws. Of course, regular citizens do not have the time or inclination to investigate the technical details of such issues, so they turn to experts to sort out the issues. "One might thus expect (or at least hope) that regardless of the tendency of predispositions and biased information processing to push people of opposing cultural outlooks apart, the need of all of them for expert guidance would cause them to gravitate toward the consensus positions among scientists," write the Yale researchers. The fond hope is that more information will tend to cause public opinions on scientific risk issues to converge. But, as the researchers show, that doesn't happen. It turns out that people don't agree on what scientific consensus is.

The Yale study conducted two kinds of surveys on their culturally-typed population. In the first one, they asked poll respondents what the majority of experts thought about global warming, nuclear waste disposal, and the risks of concealed carry gun laws. In the second survey, respondents were asked to imagine that a friend was seeking their advice about which book by an expert to read on each of the issues. The respondents were supplied with alleged summaries of each book. On each issue, one summary argued that the activity was very risky while another asserted that it was relatively harmless. The statements were assigned randomly to the pictures of older be-suited white guys with elite academic credentials as the putative authors of the books. The respondents read the summaries and were then asked if they thought each depicted author was a "trustworthy and knowledgeable expert." Remember that each author was randomly assigned to either the high- or low-risk arguments.

Depressingly, the Yale project study finds that people "more readily count someone as an expert when that person endorses a conclusion that fits their cultural predispositions." On global warming, the NAS clearly asserts that "most scientists" agree that the earth is warming and that humans are the chief cause of recent warming. According to the Yale survey, 77 percent of Egalitarian Communitarians (henceforth Egalitarians) believe that most scientists agree that the global warming is occurring, while only 24 percent of Hierarchical Individualists (henceforth Individualists) thought so. On the other hand, 55 percent of Individualists thought that scientists were divided on whether or not the earth is warming while only 20 percent of Egalitarians did. In addition, 67 percent of Egalitarians thought most scientists agreed that humans are causing the warming, while 55 percent of Individualists believe that most scientists disagree that humans are the source of warming.

On burying nuclear waste, the NAS studies maintain that there is a "strong worldwide consensus" on its safety. According to the survey, similar percentages of Egalitarians (43 percent) and Individualists (44 percent) believe that experts are divided on the issue. Nevertheless, 37 percent of Individualists believe that experts think it's safe to bury nuclear wastes, while only 21 percent of Egalitarians do. On the other hand, 18 percent of Individualists believe that most experts think it's dangerous to bury nuclear wastes, while 36 percent of Egalitarians do.

With regard to the risks of violence posed by concealed carry gun laws, the cited NAS study finds no consensus among experts. Interestingly, a plurality of both Individualists and Egalitarians believe that most experts are divided on the issue, 40 percent and 41 percent respectively. Still, 47 percent of Individualists think that most experts agree that concealed carry laws prevent violence, while 48 percent of Egalitarians believe that the expert consensus is that concealed carry laws promote violence.

Parenthetically, the Yale project doesn't look at how cultural cognition shapes the values of the researchers who construct various scientific consensuses. For example, last July, a Pew Research Center for People & the Press survey found that 52 percent of scientists described themselves as liberal while only 20 percent of the public did. Conversely, 37 percent of the public called themselves conservative while only 9 percent of scientists did. So it's not too surprising that scientists have a more positive view of the efficacy of government action than does the public. Among scientists, 58 percent disagree with the statement that "when something is run by the government it is usually inefficient and wasteful" whereas only 39 percent of the public disagree with it. Both the public and scientists are suspicious of business, believing that business does not generally strike a fair balance between profits and the public interest, 58 percent and 77 percent, respectively.

So how did the poll respondents assess the trustworthiness of the putative experts in the survey? When the depicted expert declared global warming to be risky, 89 percent of Egalitarians found him trustworthy and knowledgeable while only 23 percent of Individualists did. On the other hand, when the putative expert suggested that the dangers posed by global warming were highly uncertain, 86 percent of Individualists found him credible, while 51 percent of Egalitarians did. Division over the trustworthiness of the nuclear waste experts was not nearly as stark. When the supposed expert asserted it was dangerous to bury nuclear waste, 63 percent of Individualists found him credible, while 85 percent of Egalitarians did. And when the expert claimed it was safe to bury wastes, 78 percent of Individualists trusted him, while only 60 percent of Egalitarians did. Concealed carry brought out deep differences between Individualists and Egalitarians. When the expert in the survey declared concealed carry was risky, only 25 percent of Individualists thought him trustworthy and knowledgeable, while 78 percent of Egalitarians did. When the expert asserted that legally concealed handguns prevented crime, 83 percent of Individualists trusted him, while only 51 percent of Egalitarians did.

So how can scientific information about risks be effectively communicated to the public and policymakers? To increase the chances of securing open-minded consideration of scientific findings, the Yale researchers argue that risk communicators "must strive to present it in a way that avoids making it needlessly threatening to the identities of one or another group of culturally diverse citizens." In other research the Yale team found that Hierarchical Individualists were more open to scientific evidence of man-made global warming when coupled with the suggestion that nuclear power might be a way to address the problem.

In another study on cultural reactions to vaccinating adolescent girls against human papillomavirus (HPV), the Yale researchers used putative experts that reflected Hierarchical Individualist values (grey-haired suited men) and Egalitarian Communitarian values (denim-shirted and bearded men). When the grey-hairs opposed the vaccine, Hierarchical Individualists increased their opposition, and when the denim-shirts favored the vaccine, Egalitarian Communitarians increased their support. Then the researchers inverted the expert-argument pairing, and they found that vaccine polarization disappeared. The messengers mattered. In other words, trotting out Al Gore to argue that global warming is a crisis will do nothing to convince doubters, nor will citing Sen. James Inhofe (R-Okla.) persuade believers that it's a hoax. In fact, opinions harden, argues Yale project researcher Kahan, when advocates clearly identified with particular cultural outlooks indulge in partisan rhetoric and ridicule opponents as corrupt or devoid of reason. "This approach encourages citizens to experience scientific debates as contests between warring cultural factions—and to pick sides accordingly," he notes.

Back in December 2008, President-elect Barack Obama declared that science is "about ensuring that facts and evidence are never twisted or obscured by politics or ideology." In their latest working paper, the Yale Cultural Cognition project researchers conclude, "We believe it is more plausible to infer that both hierarchical individualists and egalitarian communitarians are fitting their perceptions of scientific consensus to their predispositions than that either has some advantage over the other in discerning what 'most expert scientists' really believe." At least we can all agree it is the other guys' politics and ideologies that are twisting facts and obscuring evidence.

Ronald Bailey is Reason's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is available from Prometheus Books.