Making low probabilities useful

This paper explores how people process information on low probability-high consequence negative events and what it will take to get individuals to be sensitive to the likelihood of these types of accidents or disasters. In a set of experiments, information is presented to individuals on the likelihood of serious accidents from a chemical facility. Comparisons are made with other risks, such as fatalities from automobile accidents, to see whether laypersons can determine the relative safety of different plants. We conclude that fairly rich context information must be available for people to be able to judge differences between low probabilities. In particular, it appears that one needs to present comparison scenarios that are located on the probability scale to evoke people's own feelings of risk. The concept of evaluability recently introduced by Hsee and his colleagues provides a useful explanation of these findings.