Verbal and Numeric Probabilities Differentially Shape Decisions

https://psyarxiv.com/ad7gw/

Decision-makers in diverse fields ranging from medicine to law to public policy depend on the clear and unbiased communication of probabilities. Expert judges often express probabilities verbally (e.g., unlikely) rather than numerically (e.g., 25% chance). Researchers have criticized the practice because verbal probabilities are vague and imprecise. However, little work has investigated the pragmatic consequences of their usage. In three online experiments (Ns = 201, 439, 435), we showed that the directionality of verbal probabilities leaked information about experts’ expectations. Receivers interpret these inferred expectations as recommendations. The inferred recommendation, in turn, influences their decisions. Compared to numeric probabilities, the directionality of verbal probabilities makes their interpretation more ambiguous due to pragmatic implicatures. We discuss how senders could improve communication fidelity by using numeric probabilities as a principal form of communicating probabilistic information, as their directionality and interpretation are less ambiguous and more consistent.

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Ryan Watkins

Professor at George Washington University

I am a Professor with Human-Technology Collaboration and Educational Technology programs at George Washington University in Washington DC. I have written 12 books and more than 100 articles, and I co-host of the Parsing Science podcast where scientists tell the stories behind their research. I am also the developer of the WeShareScience.com online platform for sharing research videos, and SciencePods.com where researchers can create free podcasts about their science. My research interests include human interactions with intelligent machines, needs, needs assessments, and instructional design.