Is there really an omission effect?

The omission effect, first described by Spranca and colleagues (Spranca, Minsk, & Baron, 1991), has since been extensively studied and repeatedly confirmed (Cushman, Murray, Gordon-McKeon, Wharton, & Greene, 2012). All else being equal, most people judge it to be morally worse to actively bring about a negative event than to passively allow that event to happen. In this paper, we provide new experimental data that challenges previous studies of the omission effect both methodologically and philosophically. We argue that previous studies have failed to control for the equivalence of rules that are violated by actions and omissions. Once equivalent norms are introduced, our results show that the omission effect is eliminated, even if the negative outcome of the behavior is foreseen and intended by the agent. We show that the omission effect does not constitute a basic, moral disposition but occurs exclusively in complex moral situations. Building on these empirical results, we cast doubt onto two influential explanations of the omission effect, the Causal Relevance Hypothesis and the Overgeneralization Hypothesis, and provide a novel explanation of the phenomenon. Furthermore, we discuss various ramifications of the interplay between our understanding of omissions and legal systems.