Consider how you would respond to the following scenario:

A patient is suffering from a life-threatening ailment. A team of pastors and parishioners assemble around the bed for an hour a day, trying a new method of prayer in the hope of curing the patient. After a week, the patient has survived the disease and is well on the way to recovery. How many more successful cases like this would you like to see before you are convinced that it was the prayer therapy that cured the patient?

Your response to this question likely depends on how deep your religious beliefs are. In past studies, religious people required significantly fewer successful replications for them to become convinced of the effectiveness of the prayer therapy, in contrast to those who were non-religious.

At first glance, this finding suggests that religious people have less exacting standards of evidence than those without religious faith. However, when we tweak the above scenario so that it’s a team of doctors and nurses instead of pastors and parishioners, and the new method is medical therapy rather than prayer therapy, we get a different set of results. In this case, both religious and non-religious people demand the same level of evidence.

Despite claims to the contrary, religious people don’t necessarily display a against science or scientific reasoning, which they seem to understand as well as non-religious people. Religious persons do, however, tend to show a bias in favor of explanations for events. But this makes sense, after all, since the supernatural is an integral part of their worldview.

However, science doesn’t proceed simply by gathering evidence to support hypotheses. Rather, it also seeks out evidence that can potentially prove a hypothesis false. For example, when we evaluate the effectiveness of a new therapy, we don’t only want to know how many patients recovered. We also want to know how many didn’t.

Until now, research has not looked at whether religious and non-religious people have different standards for weighing failed replications as evidence against a hypothesis. This was the research question that University of California, Merced psychologist Emilio Lobato and his colleagues explored in a recent article published in the journal Social Psychological and Science.

In their study, the responses of religious and non-religious persons were compared under four conditions, each based on a scenario similar to the one given above. The first two conditions asked how many successful replications (patients recovered) they wanted to see before they were convinced that the prayer or medical therapy worked, as in previous studies. The second two conditions asked how many failed replications (patients died) they needed to see before they were convinced that the prayer or medical therapy didn’t work.

In line with past research, the results showed that religious and non-religious people held similar standards for natural claims (medical therapy). This was true for both the number of successful replications needed as evidence for the claim and the number of failed replications needed as evidence against the claim. In other words, religious persons showed no bias against scientific reasoning.

Also consistent with past studies, religious people set a lower bar for accepting supernatural claims versus natural claims. Surprisingly, however, so did the non-religious participants! In other words, both groups needed to see fewer replications of the prayer therapy (compared with the medical therapy) to be convinced it was effective.

The authors speculated that since the participants live in the United States, a highly religious country, they’re still swayed by social norms to accept supernatural claims to a greater extent than their proclaimed lack of faith should allow. Furthermore, the authors mentioned, most non-religious people in this country were in fact raised in religious homes, so early experiences could still make them sympathetic to supernatural claims.

However, this sympathetic attitude towards supernatural claims by both groups didn’t extend to the evaluation of failed replications. Specifically, the religious persons held both the medical therapy and the prayer therapy to the same standard, requiring a similar number of failed replications before rejecting either. In contrast, non-religious persons required fewer failed replications of the prayer therapy (versus the medical therapy) to judge it as ineffective.

This bias against supernatural claims by non-religious people even has a name. It’s known as the Sagan standard, named after the noted cosmologist Carl Sagan, who frequently admonished: “Extraordinary claims require extraordinary evidence.” From a scientific worldview, supernatural claims are extraordinary, and so they’re evaluated at a higher standard than natural claims are.

In sum, both religious and non-religious persons seem to evaluate scientific claims—at least the sort described here—in a similar manner. However, they evaluate supernatural claims differently. Whereas religious persons require a fewer number of successful replications to accept a supernatural claim such as prayer therapy, non-religious persons reject such claims after fewer failed replications. Thus, while natural claims are evaluated from a neutral perspective, we tend to evaluate supernatural claims according to our respective worldviews.