ORGANIZATIONAL BEHAVIOR AND HUMAN DECISION PROCESSES 45, l-18 (1990) Verbal versus Numerical Probabilities: Efficiency, Biases, and the Preference Paradox

Experts (sportswriters and broadcasters) were asked to assess the proba-bilities of upcoming basketball game events. Based on these predictions, de-cision makers (students) had to rate the attractiveness of gambles. Half of the students could win real stakes based on the quality of their decisions and the outcomes of the events, while the other half were paid a flat rate. The gambles were also constructed so as to elicit the conjunction fallacy and wishful think-ing biases. While most conveyors of information used verbal terms when expressing their opinions spontaneously, most decision makers preferred to receive numerical probabilities. However, no difference between the effr-ciency of the verbal and the numerical assessments was found. The occurrence of judgmental biases was unrelated to communication mode, but the conjunc-tion fallacy was marginally related to the monetary payoff condition of the students. Two possible explanations for the communication mode preference inconsistency were examined, one of which seems to be supported by the results. A theoretical framework is suggested that accounts for the present data and former results. 8 1990 Academic press, inc