Visual display size and shape impact the accuracy of US adults' health‐risk estimates

Abstract

Health risks, when presented as ratios (e.g., two out of seven people), are challenging to understand, but visual displays can foster accurate understanding. We conducted three experiments to test how characteristics of numbers (Experiment 1), icon arrays (Experiments 1, 2, and 3), and number lines (Experiments 1 and 3) influenced people's ability to accurately estimate the risk of experiencing side effects. Participants in each experiment saw smaller‐ (e.g., 2 out of 7) and larger‐component (e.g., 264 out of 924) equivalent ratios in one of three conditions: with number lines only, with icon arrays only, or in the form of Arabic numerals with no accompanying visual. We found that risk estimates were more accurate when presented in 10 × 10 icon arrays, long horizontal 1 × 99 arrays, or number lines. We theorize that hypothetical risks can be estimated more accurately when the display affords easy translation to a percentage.

Number lines influence grade calculations, and grading scales influence perceptions and misconceptions.

“…Consistent with our hypotheses and prior work on the benefits of number line displays (e.g., Fitzsimmons et al, in press; Hamdan & Gunderson, 2017; Mielicki et al, in press; Sidney et al, 2019; Thompson, Taber, et al, 2021), we found that students estimated with less error in the number line ( M = 1.8%, SE = 0.3%) compared to no number line ( M = 2.8%, SE = 0.3%) condition, F (1, 133) = 5.39, p = .022, η p 2 = .04, averaged across grading scale. Additionally, an effect of grading scale, F (2.05, 273.18) = 56.19, p < .001, η p 2 = .30, indicated that, averaged across condition , students estimated with more error in the 387- ( M = 4.5%, SE = 0.4%) and 400-point ( M = 3.5%, SE = 0.4%) courses than the 100- ( M = 0.1%, SE = 0.1%) and 1,000-point ( M = 0.8%, SE = 0.3%) courses ( p < .001), which did not differ, p = .091.…”

“…Number lines are an effective tool to reduce whole number bias errors and increase accuracy in estimating ratios (Fitzsimmons et al, in press; Mielicki et al, in press; Thompson, Taber, et al, 2021). Number-line visual displays provide people with a quick and easy method to focus on the magnitude of rational numbers (e.g., fractions or decimals) and may help with circumventing potentially erroneous heuristics, such as mistakenly thinking that larger numerators or denominators in fractions equate to larger magnitudes (Booth & Siegler, 2008; Gunderson et al, 2019; Hamdan & Gunderson, 2017; Sidney et al, 2019, 2022).…”

Number lines can be more effective at facilitating adults’ performance on health-related ratio problems than risk ladders and icon arrays.

“…This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. (Fitzsimmons, Woodbury, et al, 2022;Mielicki et al, 2021;Sidney, Thompson, & Rivera, 2019; is to visually communicate how the part relates to the whole, and should promote a portable and durable conceptual understanding of rational number magnitudes when people encounter them in various contexts. Though substantial research in health decision-making has examined the use of visuals to help people, especially those low in numeracy, better understand risk magnitudes (Ancker et al, 2006;Bonner et al, 2021;Garcia-Retamero & Cokely, 2013Garcia-Retamero et al, 2012;Trevena et al, 2021), the goal of these visuals is to ease the mathematical burden such that people can more easily comprehend risk magnitudes perceptually (Waters et al, 2016).…”

“…Another common visual display in health communications is the icon array (Figure 1, Panel D) which includes discrete, countable icons (Galesic et al, 2009;Hess et al, 2011;Zikmund-Fisher et al, 2010). One potential advantage of icon arrays is that they may facilitate translation to percentages, which are likely more familiar (e.g., a file loading from 0% to 100%) and intuitive than other rational numbers (Fitzsimmons, Woodbury, et al, 2022;Moss & Case, 1999;Schiller, 2020). However, icon arrays led to a higher prevalence of WNB than Arabic numerals or number lines for parents estimating the likelihood of side effects from taking a hypothetical drug (Fitzsimmons, Woodbury, et al, 2022).…”

“…One potential advantage of icon arrays is that they may facilitate translation to percentages, which are likely more familiar (e.g., a file loading from 0% to 100%) and intuitive than other rational numbers (Fitzsimmons, Woodbury, et al, 2022;Moss & Case, 1999;Schiller, 2020). However, icon arrays led to a higher prevalence of WNB than Arabic numerals or number lines for parents estimating the likelihood of side effects from taking a hypothetical drug (Fitzsimmons, Woodbury, et al, 2022). The countable units in icon arrays may elicit WNB if people are more likely to use incorrect whole number strategies This document is copyrighted by the American Psychological Association or one of its allied publishers.…”