Distorting the probability of treatment success to justify treatment decisions

This research examines the value-induced bias: do people justify medical decisions by distorting their perception of relevant probabilities? Subjects were given a “close-call” decision which involved weighing one week of treatment side effects with a low probability of treatment success against seven more weeks of having the disease symptoms. They were told a numeric probability estimate of treatment success for the population as a whole. Those subjects with the ability to justify getting (not getting) treatment inflated (reduced) their numeric probability judgment of treatment success relative to those without this ability. As in cognitive dissonance reduction, risk perceptions can be distorted to align beliefs with preferences. Distorted risk perceptions may lead to suboptimal medical decisions.