Perceived probability, perceived severity, and health-protective behavior

It seems obvious that 2 key attributes of health hazards, their perceived p robability and perceived severity, do not act independently on the motivati on to engage in protective behavior. If a health problem is perceived to ha ve no chance of occurring, there should be no interest in acting against it , regardless of how serious it might be. Nevertheless, researchers seldom o bserve the expected interaction between probability and severity. A case st udy approach was used to examine how probability and severity combine to in fluence interest in protection. Ratings of motivation to act, probability, and severity for 201 hazards were collected from 12 participants, and data were analyzed for each person separately. Analyses revealed the expected Pr obability x Severity interaction. Additional calculations showed why it is difficult to detect this interaction using between-subjects designs. The da ta also revealed that people are surprisingly insensitive to variations in hazard probability when probabilities are in the moderate to high range.