Macbeth effect is an unproved theory about the link between bodily cleanliness and moral purity. It was first introduced by two psychologists Chen-Bo Zhong and Katie Lilijenquist, who conducted a series of experiments to indicate this link. In a 2006 paper in Science magazine, they stated that a threat to one’s moral purity induces the need to cleanse oneself. However, further researches have been unable to replicate these experiments using larger samples.
