While the public has a great respect for scientists, they don't trust scientists, at least when it comes to issues that also overlap with politics, like the environment.

When it comes to policy-related topics, scientists have a limited effect on the public, perhaps not because people are stupid but because some in science have moved away from being trusted guides and into being advocates, which damages the credibility of science overall.   And once those beliefs are locked in, they are difficult to change.

So while oil drilling is safe, scientists who say so now will go unheard because some in science have gone out of their way to say it isn't due to a cultural agenda.  

Increasingly, prior beliefs play an increasingly critical role in many policy disputes, muting the influence of scientific studies.   "This is not a conclusion that is likely to bring joy to the hearts of the scientific community," says Eric Smith from the University of California, co-author of a study in Public Understanding of Science.
But how do people decide which scientific claims and which experts to believe?

Some social scientists say believe claims by experts from organizations that line up with their own personal political views - the source credibility hypothesis - while the content hypothesis says that people are most likely to accept a scientific claim if it supports their existing views, regardless of the source. 

Psychologists have been looking at these hypotheses since the 1950s, but in recent decades the content hypothesis has been all but forgotten in policy research, but the investigators behind this paper believe its time for a content hypothesis revival.

The researchers used an experiment embedded in a 2002 public opinion survey of 1,475 Californians to assess the confidence people have in reports about safety studies on offshore oil drilling along the California coast. Californian voters claim to be well-versed in the debate about oil rig safety: resistance to offshore oil drilling began in response to the very first offshore operation in California in 1896(!) and has been a political hot potato ever since.

Interviewees were each asked a question, including six variables that were randomly shuffled. The question allowed researchers to evaluate both the source and the content effects at the same time. Interviewees were also asked about their core values—self-identified ideology (liberal Vs. conservative), party identification, individualism, and egalitarianism.

Egalitarianism and individualism are both core American values.   Some argue that the rise of egalitarianism (equality in the community) and the decline of individualism (self reliance, independence) due to a more progressive society explain the rise of environmental opinions in recent decades.

The first important finding was that consistency between the content of messages and a person's prior beliefs has a substantial impact. But the message source had no effect on peoples' confidence people in the scientific reports: liberals have overwhelming confidence in the claim that offshore oil drilling is riskier than previously thought, irrespective of the source, and conservatives place more faith in the message that oil drilling is safer.

Given that progressives are generally anti-business (saying pro-environment) and conservatives are generally pro-business, this is exactly what the content hypothesis would predict: the ideology and the content of the message interact.

"One finding immediately jumps out. Californians generally have more confidence in expert claims that offshore oil drilling is riskier than previously thought than they have in claims that it is safer. Fifty-eight percent of the respondents express a great deal or moderate amount of confidence in expert claims that offshore oil drilling is riskier than previously thought," says Smith.

Together, these findings raise the question of whether scientific studies are likely to have much impact on the public's views of the safety of energy sources.

The weighting towards claims that drilling is higher risk work in favor of environmental groups, giving them a substantial advantage in credibility, at least among the Californians in this study. Environmentalists most commonly warn about risks. "So if other claims by environmentalists are regarded with similar confidence, environmental groups have a strong hand in political disputes over public policy," Smith says. 

The message content hypothesis is important because it directly addresses problems in current politics: Scientists and government experts report research findings, which policy makers dispute and sometimes vote as 'false' or 'junk science'. Charges of junk science have come from many groups, both left and right, and have been directed at scientific findings in many areas—climate change, nuclear power, nuclear waste storage, genetic engineering, high-power electric transmission lines, pesticides, and oil drilling.

The findings are consistent with previous research showing that core values and prior beliefs influence whether people accept persuasive messages. But this is the first time the researchers are aware of to show that core values and prior beliefs have independent effects.

If researchers can replicate these findings in other policy areas, the influence of science on public policy debates will be in doubt.