Pseudodiagnosticity revisited.

In the psychology of reasoning and judgment, the pseudodiagnosticity task has been a major tool for the empirical investigation of people’s ability to search for diagnostic information. A novel normative analysis of this experimental paradigm is presented, by which the participants’ prevailing responses turn out not to support the generally accepted existence of a reasoning bias. The conclusions drawn do not rest on pragmatic concerns suggesting alleged divergences between the experimenter’s and participants’ reading of the task. They only rely, instead, on the demonstration that observed behavior largely conforms to optimal utility maximizing information search strategies for standard variants of the pseudodiagnosticity paradigm that have been investigated so far. It is argued that the experimental results obtained, contrary to what has recurrently been claimed, have failed to discriminate between normative and nonnormative accounts of behavior. More general implications of the analysis presented for past and future research on human information search behavior and diagnostic reasoning are discussed.