Uncertain words, uncertain texts. Perception and effects of uncertainty in biomedical communication

Literature on epistemic stance has thoroughly investigated certainty and uncertainty markers, but their effects on the reader are still unclear. This paper investigates the reader’s perception of the communication of uncertainty in biomedical texts and its effects on the reader’s emotions and decision making. Four versions of a scientific paper on the risks of egg consumption, with varying degrees of certainty, were submitted to participants in two pilots and two studies. The pilots reveal that although participants are sensitive to changes in degree of certainty, they are not so aware of the epistemic markers of uncertainty in the articles. Study 1 shows that with a different framing of the risks of egg consumption - increase of cholesterol vs. risk of heart attack -, (un)certainty has an effect both on participant’s emotions and subsequent intentions; study 2 highlights a difference between bare “lexical” certainty (simple presence of epistemic markers) and “textual” certainty (induced by contradictory sentences).