Psychophysical Numbing: When Lives Are Valued Less as the Lives at Risk Increase

Costly life-saving interventions can often be described not only in terms of the number of lives that may be saved but also in terms of the proportion of lives saved out of some total number at risk. In a phenomenon that has been referred to as psychophysical numbing (PN), Fetherstonhaugh, Slovic, Johnson, and Friedrich (1997) found that participants rated an intervention saving a fixed number of lives to be less worth investing in when more total lives were at risk (i.e., when saved lives represented a smaller proportion of the total threat or problem). In two new experiments, life-valuation correlates of PN responding, as well as manipulations of death salience, accountability, and economics focus, were explored in the context of students’ willingness to support mandatory antilock brake requirements for new cars. PN responding was pervasive, but non-PN responders were clearly distinguished by the greater overall value they placed on saving lives. Salience and accountability manipulations did not debias judgments but did tend to rule out low-effort processing as an explanation for these quantity confusions. An emphasis on economic considerations was consistently related to greater PN responding.