Outcome severity increases verbal probabilities used in dyadic communications.

Verbal probability expressions (VPEs) are interpreted as denoting higher numerical probabilities where they describe severe events, as compared to more neutral events (all else equal). Previous research suggests that this effect represents the correction of a perceived tendency for communicators to downplay the likelihood of more severe events, consistent with a rational speech act. We tested whether communicators really do downplay the likelihood of more severe events in four studies (total N = 2210). In each study, participants read four to six scenarios including a numerical probability of either a severe or non-severe negative outcome, and were asked to communicate this probability 'to a friend' with a VPE. Our results did not show that communicators downplayed the likelihood of more severe events. Participants typically provided higher VPEs to communicate the same numerical probability when that probability referred to a severe versus a non-severe event. This result was observed when participants communicated about events for which explicit actionable protective actions were highlighted (Study 1), where such actions were stated not to be possible (Studies 2 & 3), and where this was not specified (Study 4). Similar results were observed when participants chose a VPE from a pre-specified list (Studies 1, 2, & 4), and where they chose their communication freely (Study 3). The finding, coupled with those of past research, suggests that severity has a two-fold effect on subjective probability: VPEs are increased, and numerical interpretations of these VPEs are also subsequently increased.