People hold beliefs for a complex variety of reasons. Some of these beliefs may be based on facts, but others may be based on ideas that can never be proved or disproven. For example, people who are against the death penalty might base their belief partly on evidence that the death penalty does not reduce violent crime (which could later be shown to be false), and partly on the notion that the death penalty violates a fundamental human right to life. The latter is an unfalsifiable belief, because it can’t be changed purely by facts.

According to a new study in the Journal of Personality and Social Psychology, unfalsifiability is an important component of both religious and political beliefs. It allows people to hold their beliefs with more conviction, but it also alows them to become more polarized in those beliefs.

Currently, very little is known about why certain worldviews gain more mindshare in some populations, while others remain on the fringes. We also currently know only a little about how and why people continue to hold a belief in the face of contradictory evidence. Sometimes people argue on the basis of fact, questioning the quality of the evidence against their position, for example.

But it seems that people can also resort to emphasizing unfalsifiable reasons for holding a belief. This “defensive” function of unfalsifiability plays a role in both religion and politics; people can also use the unfalsifiability of their beliefs to defend them when they are threatened. The researchers also look at what they call the “offensive” function of unfalsifiability, which increases the strength of people’s religious and political beliefs.

To test the offensive function, the researchers manipulated how 103 participants perceived the falsifiability of religion. They used a survey to gauge participants’ existing level of religiosity, and then divided them randomly into two groups. Both groups read a fake news article reporting on an academic conference, with one version of the article reporting that science could one day solve the question of whether the supernatural exists, and the other version reporting that science can never know whether the supernatural exists—that is, that belief in the supernatural is unfalsifiable.

After reading, people completed a survey about their beliefs. Participants with higher religiosity saw their beliefs increase in strength if they had read the story with the unfalsifiable slant. People with lower religiosity did not show the same effect, indicating that “individual differences in the strength of … ideology predict the extent to which people turn to unfalsifiability,” write the authors.

However, they note, there could be another individual difference at work, driving both the high religiosity and the susceptibility to unfalsifiability, so they conducted another study on political beliefs. They asked 179 participants about their level of support for President Barack Obama, and then asked them to rate Obama’s performance on five issues: the health of American people, the happiness of American people, foreign policy, job creation, and the housing market. One group was told that the issues of job creation and housing could be objectively determined by evidence, while the other group was never told that Obama's performance could be assessed with data.

The results showed that unfalsifiability led to polarization of beliefs. Opponents rated Obama’s performance more negatively than supporters, but the difference was larger in those who were never told about the data. This held true across all five issues, even though only two had been earmarked as falsifiable.

This indicates that just a mention of the possibility of falsifiability had created a “general mindset” where thinking about evidence was valued, according to the researchers. While this possibly needs more investigation, the overall results seem to indicate that unfalsifiability leads to more polarized beliefs.

To test the defensive function of falsifiability, the researchers recruited 117 participants with some degree of religious belief, ranging from weak to strong. One group read a “threat” passage stating that the discovery of the Higgs boson undermines religious belief, while the other group read a “no threat” passage, which argued that the discovery is consistent with religion. Participants then rated the importance of 10 possible reasons for religious belief.

As with the “offensive” experiment on religiosity, participants with stronger religious beliefs rated unfalsifiable reasons for religious belief much more highly when they had read the threat article. People with lower religiosity showed the same effect, but to a much lesser extent.

Again, the researchers note that there are other possible explanations for this result. Unfalsifiable beliefs are possibly more central to religion, and in the face of threat, perhaps these core beliefs are emphasized. It’s difficult to separate the influence of unfalsifiability from aspects of belief that are central to a worldview.

With this in mind, they conducted a final experiment, again turning to politics. This time, they explored 174 people’s stance on same-sex marriage. All participants read a passage comparing the success of children raised by same-sex and opposite-sex parents. One version of the passage stated that both groups turned out equally well, while the other version stated that children of opposite-sex parents have better outcomes. Participants then rated whether the legality of same-sex marriage and the outcomes for children of same-sex parents are entirely matters of opinion, or entirely matters of fact.

As the researchers predicted, people who supported same-sex marriage, and read the “worse outcomes” passage contradicting their position, answered that these questions were matters purely of opinion. People who were against same-sex marriage and read the “same outcomes” passage also emphasized opinion. Meanwhile, people who had read a passage confirming their viewpoint emphasized fact. This means that people with both viewpoints retreated to unfalsifiable ideas when their position was threatened by facts.

More research is needed to corroborate these results, and to pinpoint more closely when unfalsifiability might be used as the main defensive strategy, rather than questioning the quality of evidence. However, the findings have implications for politics and science communication, the researchers suggest: reducing reliance on unfalsifiable beliefs in political discourse could lead to a reduction in polarization. Additionally, identifying why people resort to unfalsifiability, and avoiding making people defensive about their beliefs (for example, explaining that evolution does not necessarily threaten religious belief) could encourage people to let go of unfalsifiable beliefs.

Journal of Personality and Social Psychology, 2014. DOI: 10.1037/pspp0000018