. People believed dire problems-ranging from poverty to drunk driving-were less problematic upon learning the number of people they affect (Studies 1-2). Prevalence information caused medical experts to infer medication nonadherence was less dangerous, just as it led women to underestimate their true risk of contracting cancer. The big problem paradox results from an optimistic view of the world. When people believe the world is good, they assume widespread problems have been addressed and, thus, cause less harm (Studies 3-4). The big problem paradox has key implications for motivation and helping behavior (Studies 5-6). Learning the prevalence of medical conditions (i.e., chest pain, suicidal ideation) led people to think a symptomatic individual was less sick and, as a result, to help less-in violation of clinical guidelines. The finding that scale warps judgments and de-motivates action is of particular relevance in the globalized 21st century. (PsycInfo Database Record (c) 2025 APA, all rights reserved).