There may be a scientific answer for why conservatives and liberals disagree so vehemently over the existence of issues like climate change and specific types of crime.

A new study from Duke University finds that people will evaluate scientific evidence based on whether they view its policy implications as politically desirable. If they don't, then they tend to deny the problem even exists.

"Logically, the proposed solution to a problem, such as an increase in government regulation or an extension of the free market, should not influence one's belief in the problem. However, we find it does," said co-author Troy Campbell, a Ph.D. candidate at Duke's Fuqua School of Business. "The cure can be more immediately threatening than the problem."

The study, "Solution Aversion: On the Relation Between Ideology and Motivated Disbelief," appears in the November issue of the Journal of Personality and Social Psychology.

The researchers conducted three experiments (with samples ranging from 120 to 188 participants) on three different issues -- climate change, air pollution that harms lungs, and crime.

"The goal was to test, in a scientifically controlled manner, the question: Does the desirability of a solution affect beliefs in the existence of the associated problem? In other words, does what we call 'solution aversion' exist?" Campbell said.

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"We found the answer is yes. And we found it occurs in response to some of the most common solutions for popularly discussed problems."

For climate change, the researchers conducted an experiment to examine why more Republicans than Democrats seem to deny its existence, despite strong scientific evidence that supports it.

One explanation, they found, may have more to do with conservatives' general opposition to the most popular solution -- increasing government regulation -- than with any difference in fear of the climate change problem itself, as some have proposed.

Participants in the experiment, including both self-identified Republicans and Democrats, read a statement asserting that global temperatures will rise 3.2 degrees in the 21st century. They were then asked to evaluate a proposed policy solution to address the warming.

When the policy solution emphasized a tax on carbon emissions or some other form of government regulation, which is generally opposed by Republican ideology, only 22 percent of Republicans said they believed the temperatures would rise at least as much as indicated by the scientific statement they read.

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But when the proposed policy solution emphasized the free market, such as with innovative green technology, 55 percent of Republicans agreed with the scientific statement.

For Democrats, the same experiment recorded no difference in their belief, regardless of the proposed solution to climate change.

"Recognizing this effect is helpful because it allows researchers to predict not just what problems people will deny, but who will likely deny each problem," said co-author Aaron Kay, an associate professor at Fuqua. "The more threatening a solution is to a person, the more likely that person is to deny the problem."

The researchers found liberal-leaning individuals exhibited a similar aversion to solutions they viewed as politically undesirable in an experiment involving violent home break-ins. When the proposed solution called for looser versus tighter gun-control laws, those with more liberal gun-control ideologies were more likely to downplay the frequency of violent home break-ins.

"We should not just view some people or group as anti-science, anti-fact or hyper-scared of any problems," Kay said. "Instead, we should understand that certain problems have particular solutions that threaten some people and groups more than others. When we realize this, we understand those who deny the problem more and we improve our ability to better communicate with them."

Campbell added that solution aversion can help explain why political divides become so divisive and intractable.

"We argue that the political divide over many issues is just that, it's political," Campbell said. "These divides are not explained by just one party being more anti-science, but the fact that in general people deny facts that threaten their ideologies, left, right or center."

The researchers noted there are additional factors that can influence how people see the policy implications of science. Additional research using larger samples and more specific methods would provide an even clearer picture, they said.