The dependence of the conjunction fallacy on subtle linguistic factors

Summary The three experiments reported in this article are concerned with moderating conditions of the so-called conjunction fallacy. Although the conjunction of two events (A&B) is necessarily less probable than one event alone, intelligent people's judgments sometimes violate this logical principle when it is easier to think about or imagine the conjunction A&B than the component event A. It was hypothesized that the fallacy might be reduced either by a priming treatment (directing the participants' attention to the logical rule prior to the conjunctions tasks) or by a linguistic manipulation (replacing the ambiguous term probability by the term frequency. Experiment 1 shows that the bias is drastically reduced by the subtle linguistic manipulation and suggests that the fallacy is partly due to a common misunderstanding of the probability concept. The lack of a priming effect seems to imply that cueing or activation of logical schemata is not a critical factor. Experiment 2 replicates the linguistic influence under slightly modified task conditions, and Experiment 3 corroborates the ineffectiveness of the priming factor using a stronger priming treatment.