Abstract: Verbal probability is one of the ways of measuring uncertainty. People use verbal probability, such as “uncertain” and “possible”, to describe the chance that an event will happen. Verbal probability differs from numerical probability, particularly in features of vagueness, non-probabilistic operation, and semantic feature. Some remarkable phenomena and problems arise and the quality of judgment and decision making suffer in one way or another when people use verbal probability, rather than numerical probability, to measure uncertainty. The role of verbal probability in risk decision making is understudied in spite of the fact that people often use verbal probability to communicate uncertainty in their daily lives and of the great differences between verbal probability and numerical probability. Suggestions are made for future work to focus on risk decision making using verbal probability and on other potential features (e.g., the relationship between verbal/numerical probability and the dual system model, cross-cultural differences in verbal probability) and their effects on risky choices, in order to further improve our understanding of the mechanism of risk decision making.

Key words: verbal probability, numerical probability, vagueness, non-probabilistic operation, semantic feature