This past Saturday, October 15th, marked a momentous occasion in the history of cleanliness: the fourth annual Global Handwashing Day. Yes, it exists. Established by the Global Public Private Partnership for Handwashing with Soap in 2008, it has since been celebrated by schools, families, and villages across the world, from China, to Peru, to Burkina Faso. And it’s not just a gimmick: proper handwashing has the potential to save more lives than any vaccine or medical intervention and is one of the simplest and most cost-effective ways of preventing disease. But what’s more, it’s also an incredibly powerful psychological tool.
We tend to consider moral transgressions in terms of physical cleanliness
Consider this recent review from Current Directions in Psychological Science, which explores the consequences that hand washing has on the mind. The series of studies that the authors explore take as their starting point the historically close association between physical disgust and moral disgust: when we perceive a moral transgression, we tend to react in a similar way as we would to something that is physically off-putting, such as spoiled food or physical contaminants in the environment. We recoil in the same fashion; our face scrunches up in the same repulsed expression; even our brain lights up in overlapping neural networks, evoking similar subjective feelings in both instances.
And when we think about morality, we tend to think about it in terms of physical cleanliness. In one demonstration of this effect, researchers asked people to think abut a past behavior that was either moral or immoral. Those who thought about immoral acts were later far more likely to fill in word fragments such as W _ _ H and S _ _ P with words related to cleanliness, such as wash and soap, whereas no such effect was observed in any other group. On the flip side, people who were exposed to either a messy room, a stinky smell (including a “fart spray” in one study), or a video that showed a dirty toilet were more likely to judge others’ moral transgressions as more severe and more deserving of punishment than people who made the same judgments while sitting in a clean room.