The rise and fall of scary numbers: The effect of perceived trends on future estimates, severity ratings, and help‐allocations in a cancer context

Behavioral Decision Making

et al. 2019

Self Cite

Agreements and disagreements between expert statements influence lay people's beliefs. But few studies have examined what is perceived as a disagreement. We report six experiments where people rated agreement between pairs of probabilistic statements about environmental events, attributed to two different experts or to the same expert at two different points in time. The statements differed in frame, by focusing on complementary outcomes (45% probability that smog will have negative health effects vs. 55% probability that it will not have such effects), in probability level (45% vs. 55% probability of negative effects), or in both respects. Opposite frames strengthened disagreement when combined with different probability levels. Approximate probabilities can be “framed” in yet another way by indicating reference values they are “over” or “under”. Statements that use different directional verbal terms (over vs. under 50%) indicated greater disagreement than statements with the same directional term but different probability levels (over 50% vs. over 70%). Framing and directional terms similarly affected consistency judgments when both statements were issued by the same expert at different occasions. The effect of framing on perceived agreement was significant for medium (10 and 20 percentage points) differences between probabilities, whereas the effect of directional term was stable for numerical differences up to 40 percentage points. To emphasize agreement between different estimates, they should be framed in the same way. To accentuate disagreements or changes of opinion, opposite framings should be used.

Section: Discussionsupporting

confidence: 74%

Framing experts' (dis)agreements about uncertain environmental events

Løhre

Sobków

Behavioral Decision Making

et al. 2019

Self Cite

“…Everyday observations and research show that people do not need much evidence to infer a trend. Two data points may be sufficient to indicate a process of growth or decline and can lead observers to formulate hypotheses of monotonous and even linear increases or decreases (Erlandsson, Hohle, Løhre, & Västfjäll, ; Hohle & Teigen, ). When probabilities are changed or revised, it is easy to imagine that a process of continued revision will take place.…”

Section: Discussionmentioning

confidence: 99%

More than 50% or Less than 70% Chance: Pragmatic Implications of Single‐Bound Probability Estimates

Behavioral Decision Making

Teigen

2017

Self Cite

Probability estimates can be given as ranges or uncertainty intervals, where often only one of the interval bounds (lower or upper) is specified. For instance, a climate forecast can describe La Niña as having "more than 70% chance" or "less than 90% chance" of occurring. In three experiments, we studied how research participants perceived climate-related forecasts expressed with lower-bound ("over X% chance") or upper-bound ("under Y% chance") probability statements. Results indicate that such single-bound statements give pragmatic information in addition to the numeric probabilities they convey. First, the studies show that these statements are directional, leading the listeners' attention in opposite directions. "Over" statements guide attention towards the possible occurrence of the event and are explained by reasons for why it might happen, while "under" statements direct attention to its possible non-occurrence and are more often explained by reasons for why the target event might not appear, corresponding to positive (it is possible) versus negative (it is uncertain) verbal probabilities. Second, boundaries were found to reveal the forecaster's beliefs and could be perceived as indicative of an increasing or a decreasing trend. Single-bound probability estimates are therefore not neutral communications of probability level but might "leak" information about the speaker's expectations and about past and future developments of the forecast.

“…A recent study has replicated the trend effect for interval forecasts. A forecast where the interval for expected outcomes had widened was predicted to continue widening, while a narrowed interval was believed to become still narrower in the future (Løhre, 2017). Even single forecasts can suggest a trend, depending upon the way they are described.…”

Section: The Trend Effectmentioning

confidence: 99%

“…Trends created by revised probabilities may affect actual behavior. People were willing to donate more money to research on a cancer type whose death risk has increased rather than decreased (Erlandsson, Hohle, Løhre, & Västfjäll, 2017), and preferred a product whose risk of a defect was adjusted downwards compared to upwards (Maglio & Polman, 2016). Importantly, in all these studies the current forecasts were the same, only the previous forecasts differed by being higher or lower than the most recent one.…”

Section: The Trend Effectmentioning

confidence: 99%

See 1 more Smart Citation

When probabilities change: perceptions and implications of trends in uncertain climate forecasts

Journal of Risk Research

Teigen

2018

Self Cite

Past research has revealed a trend effect when people are faced with a revised probabilistic forecast: A forecasted event that has become more (vs. less) certain is taken to signal a trend towards even stronger (weaker) certainty in future revisions of the forecast. The present paper expands this finding by exploring the boundary conditions of the trend effect and how it affects judgments of the forecaster. In Study 1, the trend effect was shown to persist when receivers process the forecast more deliberately, by considering reasons for the revision. In Study 2, trend continuation was predicted even when the two forecasts were made by different experts at different points in time. Study 3 demonstrated that the effect disappears when receivers are given an earlier forecast disrupting the linearity of the trend (e.g., a 60%-70% sequence preceded by a 70% forecast). In Study 4, two forecasters were perceived as more in agreement when revising divergent probabilities in the same rather than in opposite directions. If the event occurs, a forecast with downgraded probability (e.g. from 50% to 40%) was judged to be less accurate than an equally uncertain single forecast (40%).These results demonstrate the robustness of the trend effect based on two forecasts, affecting not only receivers' expectations of what comes next, but also their perceptions of the forecaster and of forecast accuracy. The findings have implications for how people communicate and understand risks and other uncertain events in areas such as climate science, weather prediction, political science and medicine.