The effect of effects on effectiveness: A boon-bane asymmetry

Beliefs about how effective a cause will be at achieving possible outcomes are critical inputs into a range of decisions, from how to treat an illness to which products to purchase. We identify scope—the number of distinct outcomes a cause is known to achieve—as an important input into judgments of efficacy. We compare causes that lead to worse outcomes (i.e., banes) to those leading to improvements (i.e., boons). People believe that banes with broader scope (i.e., those that lead to more possible outcomes) are more effective and lead to stronger outcomes. In contrast, people believe that boons with narrower scope (i.e., those that lead to fewer possible outcomes) are more effective and lead to stronger outcomes. We document this pattern across four experiments, finding support for differences in mental models for boons and banes.