Sensitivity to shifts in probability of harm and benefit in moral dilemmas.

Psychologists and philosophers who pose moral dilemmas to understand moral judgment typically specify outcomes as certain to occur in them. This contrasts with real-life moral decision-making, which is almost always infused with probabilities (e.g., the probability of a given outcome if an action is or is not taken). Seven studies examine sensitivity to the size and location of shifts in probabilities of outcomes that would result from action in moral dilemmas. We find that moral judgments differ between actions that result in an equal increase in probability of harm (equal size), but have different end-states (e.g., an increase in harm probability from 25% to 50% or from 50% to 75%). This deviation from expected value is robust under separate evaluation, and increases when the comparison between shifts is made explicit under simultaneous evaluation. Consistent with the centrality of perceived harm in some models of moral judgment, perceived harm partially mediates sensitivity to location of harm probability shift. Unlike for shifts in harm probabilities, participants are insensitive to the location of shifts in probability of beneficial outcomes. They are also insensitive to the location of shifts in probability of analogous monetary losses and gains, suggesting an asymmetry between harm and benefit in moral reasoning, as well as an asymmetry between moral and monetary decision-making more broadly. Implications for normative philosophical theory and moral psychological theory, as well as practical applications, are discussed.