Does Cleanliness Influence Moral Judgments?

Abstract

Schnall, Benton, and Harvey (2008) hypothesized that physical cleanliness reduces the severity of moral judgments. In support of this idea, they found that individuals make less severe judgments when they are primed with the concept of cleanliness (Exp. 1) and when they wash their hands after experiencing disgust (Exp. 2). We conducted direct replications of both studies using materials supplied by the original authors. We did not find evidence that physical cleanliness reduced the severity of moral judgments using samples sizes that provided over .99 power to detect the original effect sizes. Our estimates of the overall effect size were much smaller than estimates from Experiment 1 (original d = −0.60, 95% CI [−1.23, 0.04], N = 40; replication d = −0.01, 95% CI [−0.28, 0.26], N = 208) and Experiment 2 (original d = −0.85, 95% CI [−1.47, −0.22], N = 43; replication d = 0.01, 95% CI [−.34, 0.36], N = 126). These findings suggest that the population effect sizes are probably substantially smaller than the original estimates. Researchers investigating the connections between cleanliness and morality should therefore use large sample sizes to have the necessary power to detect subtle effects.