S. Schnall et al., “With a Clean Conscience: Cleanliness Reduces the Severity of Moral Judgments,” Psych Sci 19 (2008): 1219; K. Kaspar et al., “Hand Washing Induces a Clean Slate Effect in Moral Judgments: A Pupillometry and Eye-Tracking Study,” Sci Rep 5 (2015): 10471.