Experienced Probabilities Increase Understanding of Diagnostic Test Results in Younger and Older Adults

Background. With advancing age, the frequency of medical screening increases. Interpreting the results of medical tests involves estimation of posterior probabilities such as positive predictive values (PPVs) and negative predictive values (NPVs). Both laypeople and experts are typically poor at estimating posterior probabilities when the relevant statistics are communicated descriptively. The current study examined whether an experience format would improve posterior probability judgments in younger and older adults, relative to a description format. Method. Eighty younger (ages 17–34 y) and 80 older adults (ages 65–87 y) completed an experimental task in which information about medical screening tests for 2 fictitious diseases was presented either through description or experience. Participants in the descriptive format read a passage containing statistical information, whereas participants in the experience format viewed a slideshow of representative cases that illustrated the relative frequency of the disease as well as the relative frequency of positive and negative test results. Results. Both younger and older adults made more accurate posterior probability estimates in the experience format, relative to the description format. In the descriptive format, PPVs were overestimated and NPVs were underestimated. Regardless of format type, participants reported that they would prefer to rely on a physician to make medical decisions on their behalf compared with themselves. Discussion. These findings are indicative of a description-experience gap in Bayesian inference, and they suggest possible avenues for enhancing medical risk communication for both younger and older patients.