Evidence for beliefs: What matters, and what doesn't

The Flying Spaghetti Monster (source: verganza.org) is a satirical retort to advocates of "intelligent design," created as a joke to mock the belief that some "intelligent designer" created life. While the Flying Spaghetti Monster is funny, no one takes it seriously. Meanwhile, belief in a Christian God is stronger than ever, and advocates of the theory of evolution are unshaking in their support.

So what's the difference? Why do people hold some beliefs strongly, but readily discard others? Jesse Preston and Nicholas Epley have designed a technique to examine the types of evidence people are more likely to accept in support of their beliefs. They asked Boston commuters to fill out a survey in a train station. One group read a statement summarizing research on personal relationships:

Psychologists have argued that, whether choosing friends or falling in love, we are most attracted to people whose traits are similar to our own. There seems to be wisdom in the old saying "Birds of a feather flock together."

The second group read a similar statement about the relationship between self-esteem and aggression:

Although intuition suggests that people who are depressed or low in self-esteem are more likely to be violent or aggressive towards others, some research demonstrates exactly the opposite. In fact, people who are high in self-esteem are more likely to be aggressive toward other people.

These two findings were chosen because, though they are familiar to psychologists, they would probably be surprising to average individuals -- so any manipulation of these beliefs was likely to be unrelated to previously held beliefs. Next the commuters were asked to write down one of two types of evidence that might support the statement they had just read. They either wrote down "implications or observations that this research finding would explain," or reasons "why this finding would come about." Then each group was asked how important, meaningful, and relevant the findings were for them. Here are the results:

When people wrote about the implications of the research -- how it could be applied to the real world, they believed it was significantly more valuable than when they tried to explain why the research might be true. So without offering any evidence on the research at all, Preston and Epley were able to affect how people felt about the research: applications matter much more to people than explanations.

But what about religious beliefs? Aren't these beliefs so strongly held that no amount of manipulation by researchers can change them? Preston and Epley conducted a modified version of this same experiment with Harvard students who professed a belief in God (atheists in the survey group were administered a similar questionnaire, but their results were discarded). As before, participants were asked to write down either explanations ("observations that can explain God's behavior") or applications ("observations that God can explain"). Half the participants wrote down three items, and half were told to write down ten (though many were unable to come up with this number of examples). As before, they were also asked to rate the value of their belief in God on a 0-10 scale. Here are the results:

Students who wrote down applications of belief in God perceived the value of that belief to be significantly higher than those who wrote explanations, and students who wrote more applications rated the value of their belief as significantly higher than those who wrote fewer applications.

It should be noted that the manipulations in these experiments did not impact the perceived truth of beliefs, only the value of those beliefs. In the first experiment, studying belief in psychology research, about 50 to 60 percent of respondents believed the research to be true, whether they were in the explanations or applications group. None of the respondents to the religious survey changed their belief in God. Nonetheless, the fact that the perceived value of even religious beliefs can be so readily manipulated in such a brief experiment is quite astonishing.

Evolution scientists may want to take note of these findings as they attempt to inform the public of the value of their research: people appear to value applications over explanations -- so instead of explaining the mechanism of evolution, a better tact appears to be to emphasize the applications. The fact that many useful vaccines have been developed based on the theory of evolution will impress more people than research showing how DNA can mutate and cause organisms to change.

And followers of the Flying Spaghetti Monster, if they want more adherents to value their ideas, would be well advised to show how his noodly appendages can touch all of us, in our daily lives.

Preston, J., & Epley, N. (2005). Explanations versus applications: The explanatory power of valuable beliefs. Psychological Science, 16(10), 826-832.