Measuring Variants of Uncertainty in Political Speech

Politicians operate in complex informational environments, where they continuously confront uncertainty stemming from conflicting interests and unpredictability. One way in which they handle the uncertainty inherent to their work is by verbalizing what they do and do not know. While political communication studies have measured politicians' strategic communication of concepts adjacent to uncertainty, such as politicians’ verbal projection of confidence (e.g. LIWC’s “clout” metric in Jordan et al., 2019) or purposefully ambiguous messaging (e.g. Lefevere, 2024), there is scant research into how politicians communicate (un)certainty specifically – that is, how they express the level of knowledge they have about the topic at hand. This is an important gap to address, considering uncertainty communication can shape individuals’ subsequent behavior (Batteux et al., 2022; Vives et al., 2023). How do politicians communicate uncertainty in practice, and what can this tell us about the role of uncertainty in political communication? The answer may lie in politicians’ framing of the source of the uncertainty. Namely, do they attribute uncertainty to a gap in their own knowledge (epistemic uncertainty), or to the uncontrollable, inherent randomness of the world (aleatory uncertainty)? A growing body of research shows that these variants of uncertainty are intuitively understood from language by speakers and listeners alike (Juanchich et al., 2017; Ülkümen et al., 2016). In political speech, selectively expressing epistemic or aleatory uncertainty may enable politicians to be honest about the uncertainty (e.g. by expressing aleatory uncertainty) while taking care not to lose their credibility (e.g. by hiding epistemic uncertainty). To explore the role of uncertainty in political communication , we utilize open-source gLLM models to label the main variants of uncertainty - epistemic (knowability) and aleatory (randomness) - in U.S. Congress member's speeches from 1996 to 2024. We examine how the frequency of uncertainty and certainty expressions varies both within and between individuals, analyzing the predictive nature of variables such as ideology, gender, security of district, and time until the next election. Our findings provide insights into a rarely studied communication strategy that politicians may employ for political advantage: one of adjusting their expressions of (different variants of) uncertainty. Insights from this study are therefore relevant for political communication scholars in a variety of fields, including leadership studies and crisis management.