How bad is a 10% chance of losing a toe? Judgments of probabilistic conditions by doctors and laypeople.

We presented a Web questionnaire to 139 physicians and medical researchers and 109 laypeople. The subjects made judgments of badness and importance of prevention for eight medical conditions at each of seven different probability levels. By assuming that the response to each of the 56 risks was monotonically related to transformations of the probability and of the disutility of the condition, we could assess the relative effect of probability and disutility on each subject's judgments. Physicians' judgments were more sensitive than laypeople's judgments to changes in probability. Older and female laypeople were less sensitive to probability (and correspondingly, more responsive to differences in severity among medical conditions). Laypeople varied more than physicians in their responsiveness to probability. These results point to general individual differences in the effect of probability on evaluations of medical risks. They may also provide insight into causes and noncauses of physician-patient miscommunication.