Do people really prefer verbal probabilities?

Abstract

When people communicate uncertainty, do they prefer to use words (e.g., "a chance", "possible") or numbers (e.g., "20%", "a 1 in 2 chance")? To answer this question, past research drew from a range of methodologies, yet failed to provide a clear-cut answer. Building on a review of existing methodologies, theoretical accounts and empirical findings, we tested the hypothesis that the preference for a particular format is driven by the variant of uncertainty that people experience. We expected that epistemic uncertainty would be more often communicated in words, whereas distributional uncertainty would be more often communicated in numbers; for the dispositional uncertainty, we expected that an individual's disposition would be more often communicated in words, whereas dispositions from the world would be more often communicated numerically. In three experiments (one oral, two written), participants communicated their uncertainty regarding two outcomes per variants of uncertainty: epistemic, dispositional and distributional. Overall, participants communicated their uncertainty more often in words, but this preference depended on the variants of uncertainty. Participants conveyed their epistemic and dispositional uncertainties more often in words and their distributional uncertainty in numbers (Experiments 1 and 2) but this effect was greatly reduced when the precision of uncertainty was held constant (Experiment 3), pointing out the key role of uncertainty vagueness. We have reviewed the implications of our findings for the existing accounts of format preferences.

Most family physicians report communicating the risks of adverse drug reactions in words (vs. numbers)

“…In the communication trade‐off between being precise (and blunt and accountable) or vague (and tactful and less accountable), the second option was more attractive to the majority of the physicians for communicating the risk of adverse drug reactions to patients. The family physicians' preference for words is consistent with most of the literature on format preference (Du et al, ; Gonzalez‐Vallejo, Erev, & Wallsten, 1994; Olson & Budescu, ; Wallsten et al, ) but is at odds with findings showing that events that have a precise probability (such as those provided in drug leaflets) are more often communicated in numbers (Juanchich & Sirota, ). Because of the vagueness and proneness of verbal quantifiers to interpretation biases, their frequent usage may pose a threat to the ability of patients to provide informed consent.…”

“…Prior research has shown that "lay" people prefer to communicate their uncertainty verbally rather than numerically (Du et al, 2013;Erev & Cohen, 1990;Juanchich & Sirota, 2019a;Xu, Ye, & Li, 2009), although the opposite pattern has sometimes been documented too (Du et al, 2013;Olson & Budescu, 1997). Little data exist from health professionals, but they consistently indicate a preference for verbal risk quantification.…”

“…Given that most drug leaflets feature the numerical probabilities of different adverse drug reactions (Study 3, Sirota et al, ), we could expect that family physicians would use them. Although in general people prefer to communicate risk with words, they also report that they would actually use a numerical estimate if such a precise estimate was available or could be easily computed (Juanchich & Sirota, ; Olson & Budescu, ; Wallsten, Budescu, Zwick, & Kemp, ). For example, most people produced a numerical prediction to describe events for which a precise probability could be computed (e.g., the probability of selecting a red card from a deck of cards), whereas people favoured words for events where uncertainty stemmed from a lack of knowledge (e.g., whether Reynes is a village in France; Juanchich & Sirota, ).…”

Arithmetic computation with probability words and numbers

“…In these and other areas (e.g., Morgan, 1998), experts typically assess and communicate probabilities with words such as "likely" rather than numeric quantifiers such as "75% chance". This is true even in stereotypically quantitative professions such as accounting (Kolesnika, Silska-Gembka, & Gierusz, 2019), and is consistent with the preference of communication senders who tend to favor the use of verbal over numeric probabilities Juanchich & Sirota, 2020;Olson & Budescu, 1997;Wallsten, Budescu, Zwick, & Kemp, 1993).…”

Numerically Bounded Linguistic Probability Schemes Are Unlikely to Communicate Uncertainty Effectively

“…One problem with using NBLP schemes to describe scientific uncertainties to the public is the well documented finding that people generally prefer to receive such communications in numerical form, even while they generally prefer to communicate them verbally (Erev & Cohen, 1990; Juanchich & Sirota, 2019; Murphy et al, 1980; Olson & Budescu, 1997; Wallsten et al, 1993). Erev and Cohen (1990) introduced the term preference paradox to denote these simultaneous preferences, often in the same individual.…”