The Directionality of Verbal Probability Expressions: Effects on Decisions, Predictions, and Probabilistic Reasoning

Area of Science:

• Cognitive Psychology
• Linguistics
• Decision Science

Background:

• Verbal expressions of uncertainty can be categorized as positive (suggesting occurrence) or negative (highlighting nonoccurrence).
• The directionality of these phrases is linked to, but distinct from, statistical p-values.
• The choice of verbal probabilistic phrases influences subsequent predictions and decisions.

Purpose of the Study:

• To investigate how the directionality of verbal uncertainty phrases affects decision-making and probabilistic reasoning.
• To compare the impact of positive versus negative uncertainty phrasing on judgments and inferences.
• To determine if verbal probabilities are vague or if they guide specific inferential processes.

Main Methods:

• Four experiments were conducted to test the influence of verbal uncertainty phrases.
• Experiment 1 examined how different phrases affect treatment recommendations.
• Experiments 2 and 3 explored decision-making differences based on phrase formulation.
• Experiment 4 analyzed conjunction and disjunction errors in probabilistic reasoning.

Main Results:

• Phrases like "some possibility" lead to different recommendations than "quite uncertain," even with identical probabilities.
• Individuals using positive phrasing make different decisions compared to those using equivalent negative phrasing.
• Negative phrases reduce errors in reasoning about combined uncertain events (conjunctions).
• Positive phrases reduce errors in reasoning about alternative uncertain events (disjunctions).

Conclusions:

• Verbal probabilistic phrases are not merely vague but actively guide the type of inferences drawn.
• The directionality (positive vs. negative) of uncertainty language significantly impacts judgment and decision-making.
• Understanding the inferential implications of verbal uncertainty is crucial for effective communication in science and everyday life.