"R" you getting this? Factors contributing to the public's understanding, evaluation, and use of basic reproduction numbers for infectious diseases.

BACKGROUND: We (1) examined the effects of evaluative labels and visual aids on people's understanding, evaluation, and use of the COVID-19 reproduction number (or "r-number"), (2) examined whether people's perceived susceptibility and (intended) adherence to preventive measures changed after being exposed to the r-number, and (3) explored whether these effects and changes depended on people's numeracy skills. METHODS: In an online experiment, participants from a large Dutch representative sample (N = 1,168) received information about the COVID-19 r-number displayed on the corona dashboard of the Dutch Ministry of Health, Welfare and Sport. The r-number was either presented with or without a categorical line display (i.e., evaluative label) and with or without an icon-based tree diagram (i.e., visual aid) explaining how the number works. Regarding people's use of the statistic, we measured perceived susceptibility to COVID-19 and adherence (intention) to five preventive measures before and after exposure to the r-number. After exposure, we also measured participants' understanding, perceived usefulness, affective and cognitive evaluation, and objective numeracy. RESULTS: About 56% of participants correctly interpreted the r-number, with highly numerate people having better understanding than less numerate people. Information about the r-number was perceived as more useful when presented with a visual aid. There were no differences across experimental conditions in people's understanding, affective, and cognitive evaluations. Finally, independent of experimental conditions, intention to adhere to preventive measures was higher after seeing the r-number, but only among highly numerate people. CONCLUSIONS: Although evaluative labels and visual aids did not facilitate people's understanding and evaluation of the r-number, our results show that the statistic is perceived as useful and may be used to stimulate adherence to preventive measures. Policy makers and public health communicators are advised to clearly explain why they are giving these numbers to - especially - the less numerate people, but also how people could use them for behavior change to combat the spread of virus during a pandemic.

It is, uh, very likely? The impact of prosodic uncertainty cues on the perception and interpretation of spoken verbal probability phrases.

People typically use verbal probability phrases when discussing risks ("It is likely that this treatment will work"), both in written and spoken communication. When speakers are uncertain about risks, they can nonverbally signal this uncertainty by using prosodic cues, such as a rising, question-like intonation or a filled pause ("uh"). We experimentally studied the effects of these two prosodic cues on the listener's perceived speaker certainty and numerical interpretation of spoken verbal probability phrases. Participants (N = 115) listened to various verbal probability phrases that were uttered with a rising or falling global intonation and with or without a filled pause before the probability phrase. For each phrase, they gave a point estimate of their numerical interpretation in percentages and indicated how certain they thought the speaker was about the correctness of the probability phrase. Speakers were perceived as least certain when the verbal probability phrases were spoken with both prosodic uncertainty cues. Interpretation of verbal probability phrases varied widely across participants, especially when rising intonation was produced by the speaker. Overall, high probability phrases (e.g., "very likely") were estimated as lower (and low probability phrases, such as "unlikely," as higher) when they were uttered with a rising intonation. The effects of filled pauses were less pronounced, as were the uncertainty effects for medium probability phrases (e.g., "probable"). These results stress the importance of nonverbal communication when verbally communicating risks and probabilities to people, for example, in the context of doctor-patient communication.