The Moral Dilution Effect: Irrelevant Information Influences Judgments of Moral Character

It is reasonable to expect that when making a judgment, we only consider the relevant (or diagnostic) information, and that non-relevant (non-diagnostic) information should not, and thus does not, influence our judgments. Previous research has shown that this is not always the case and that the inclusion of non-diagnostic information can lead to less extreme judgments. This phenomenon is known as the dilution effect, and it has been observed for a range of judgments, including product evaluations, probability judgments, and predictions relating to people’s behavior. The dilution effect has been explained as a consequence of the representativeness heuristic, such that the inclusion of non-diagnostic information reduces the match between the target and a typical member of the category. Consistent with this notion and recent approaches to moral decision making, we predict that the dilution effect should be observed for judgments about morality. . Across four studies (total N = 2,585), we tested for the dilution effect on judgments of morally bad actors and morally good actors. Overall, our results showed a dilution effect for judgments of both good and bad actors. People's moral evaluations of both good and bad actors were less extreme when the descriptions included non-diagnostic information. We showed that this effect is not the result of humanization, and we found the robustness of the effect appears to be moderated by valence, with a more robust effect for bad actors. Our results highlight avenues for future research.