Interpretations and assessments of verbal probability expressions

Abstract

Verbal probability expressions convey both a more or less precise numerical meaning, and they have a positive or negative directionality. Positive phrases, such as possible and likely , focus on the occurrence of the target event, negative phrases, such as uncertain and unlikely , focus on it's non-occurrence.

The first part of this paper investigates whether participants primarily would interpret specific verbal probability expressions as conveying a numerical meaning, or if they would focus on the directionality of the verbal phrases. The results indicate that participants primarily have treated the verbal phrases as conveying probabilistic information, and seem to have been less influenced by the semantic clues inherent in the positive or negative directionality of the phrases. This does not mean that participants have treated the phrases as exclusively conveying a numerical meaning, but rather that they seem to have weighted the probabilistic content more than the semantic content.

The second part of this paper compares how people assign verbal and numerical probability estimates to uncertain outcomes. The saliens of different state space partitions are manipulated, and we see if participants are consistent in the way they assign verbal and numerical estimates to the same situation. It is argued that asking for numerical estimates puts a stronger emphasis on the rule-based aspect of assigning probabilities, and leads to more participants assigning probabilities in accord with the formal rules of probability.