People who believe most strongly in God tend to make an especially strong psychological connection between feeling clean and seeing their own behavior as good and moral, according to a study to be published in Social Psychology and Personality Science.

A significant body of psychological research shows that the metaphorical connection between morality and cleanliness (for example when people speak or having a “clean conscience,” or saying that behavior of which they disapprove “makes them sick”), is deeply rooted in human psychology. Neuroimaging studies support the idea that the same brain systems are involved in processing the emotions related to physical disgust and moral disgust. However, there is also evidence that these metaphorical connections are not necessarily hardwired, but are learned through exposure to them in one’s cultural surroundings. Religious groups may be one of the main places that people learn to associate being clean with morality in this way, because of the emphasis many religions place on ritual and spiritual cleanliness.

A study conducted by Adam Fetterman, of the University of Essex, sought to quantify how religion affects the way people associate cleanliness with morality in their daily lives. A sample of 135 college students was monitored for a period of two weeks. At the beginning of the study, the students indicated the extent to which they believed in God. Each evening for two weeks, they then reported how they had behaved on two morality-related measures (whether they had given into impulses, and whether they had helped others), how much they had felt guilty or anxious, and how clean they had felt.

In keeping with previous findings, students said that they felt cleaner on days when they had behaved morally, by avoiding negative impulses and by helping others. What this study found that was new was that this relationship was much stronger among students who believed most strongly in God. The most devout felt much cleaner on days when they saw their actions as more moral, in comparison with the days they acted impulsively and were unhelpful. Those who did not believe in God felt only slightly cleaner under the same circumstances.

These religious differences were even more pronounced when it came to the relationship between feeling clean and feeling good about oneself. Highly religious people were much less prone to feeling guilty or anxious about themselves on days when they felt clean. Among those who were less religious, feeling clean had no bearing on those negative emotions.

The study’s author concludes that the psychological association between morality and cleanliness is probably reinforced by religious teachings, explaining the differences he observed between those who believed strongly in God and those who did not. He also suggests that highly religious people may be more likely to rely on emotional styles of cognitive processing over rational ones. While it may not confirm the adage that cleanliness is next to Godliness, this study certainly seems to support the idea that the two may be closely intertwined.