The Journal of Experimental Psychology defines something I think we’ve all had a feeling about – that the more you encounter a bad deed (or hear it described in, say, a televised courtroom conflict) the less “bad” it seems. The University of North Carolina researchers studying this unfortunate human tendency have called it the moral repetition effect:
Reports of moral transgressions can “go viral” through gossip, continuous news coverage, and social media. When they do, the same person is likely to hear about the same transgression multiple times. The present research demonstrates that people will judge the same transgression less severely after repeatedly encountering an identical description of it. I present seven experiments (six of which were preregistered; 73,265 observations from 3,301 online participants and urban residents holding 55 nationalities). Participants rated fake-news sharing, real and hypothetical business transgressions, violations of fundamental “moral foundations,” and various everyday wrongdoings as less unethical and less deserving of punishment if they had been shown descriptions of these behaviors previously. Results suggest that affect plays an important role in this moral repetition effect. Repeated exposure to a description of a transgression reduced the negative affect that the transgression elicited, and less-negative affect meant less-harsh moral judgments. Moreover, instructing participants to base their moral judgments on reason, rather than emotion, eliminated the moral repetition effect. An alternative explanation based on perceptions of social norms received only mixed support. The results extend understanding of when and how repetition influences judgment, and they reveal a new way in which moral judgments are biased by reliance on affect. The more people who hear about a transgression, the wider moral outrage will spread; but the more times an individual hears about it, the less outraged that person may be.
Emphasis added.