Non-verbal uncertainty cues impact assessments of verbal probability information

Abstract

In spoken communication, verbal probability phrases (e.g. likely, almost never, certain) play a central role in conveying uncertainty. While prior research has largely focused on how such expressions are interpreted in written form, growing attention is being paid to the role of non-verbal cues in shaping uncertainty interpretation in multimodal communication. This pre-registered 2×2 within-subjects experiment (N = 100) contributes to this emerging field by investigating how auditory (rising intonation) and visual (marked facial expressions) uncertainty cues influence assessments of verbal probability information, by focusing on recipients’ perception of speaker certainty and the numerical interpretation of probability phrases. Both rising intonation and marked facial expressions independently reduced perceived speaker certainty and, in most cases, increased recipients’ variability in numerical interpretations. Notably, the combination of both cues produced the lowest perceived speaker certainty, though no additive effect on interpretive variability was observed. These findings highlight the importance of integrating non-verbal signals into theoretical models of risk and uncertainty communication and invite future research to investigate how multimodal uncertainty cues work in real-world, high-stakes contexts such as medical consultations or public risk communication.