Perceived certainty based on verbal probability phrases: Effect of directionality and its dependence on method

Verbal probability phrases (e.g. “possible” or “doubtful”) have a feature called “directionality” (Teigen & Brun, 1995), which focuses listeners on event occurrence or nonoccurrence. We conducted an experiment about certainty estimations based on verbal probabilities in order to examine the effect of directionality on perceived certainty. In measuring perceived certainty, we used scale‐based method involving responses with a scale (e.g. 101 points' scale, 0 = unlikely to 100 = likely) and numerical method involving responses such as “50%.” We found that, although the effect of directionality on perceived certainty was observed in using the scale‐based method, the effect disappeared when the numerical method was used. We discuss these results from two types of information processing (intuitive, associative processing and deliberate, rule‐based processing).