Effects of Numerical Versus Foreground-Only Icon Displays on Understanding of Risk Magnitudes

Abstract

The aim of this work is to advance knowledge of how to measure gist and verbatim understanding of risk magnitude information and to apply this knowledge to address whether graphics that focus on the number of people affected (the numerator of the risk ratio, i.e., the foreground) are effective displays for increasing (a) understanding of absolute and relative risk magnitudes and (b) risk avoidance. In 2 experiments, the authors examined the effects of a graphical display that used icons to represent the foreground information on measures of understanding (Experiments 1 and 2) and on perceived risk, affect, and risk aversion (Experiment 2). Consistent with prior findings, this foreground-only graphical display increased perceived risk and risk aversion; however, it also led to decreased understanding of absolute (although not relative) risk magnitudes. Methodologically, this work shows the importance of distinguishing understanding of absolute risk from understanding of relative risk magnitudes, and the need to assess gist knowledge of both types of risk. Substantively, this work shows that although using foreground-only graphical displays is an appealing risk communication strategy to increase risk aversion, doing so comes at the cost of decreased understanding of absolute risk magnitudes.

Acknowledgments

We thank Yasmina Okan and Wändi Bruine de Bruin for helpful conversations regarding the ideas presented in the paper, and William Fleeson for his useful suggestions regarding the data analysis for Experiment 1.

Notes

¹This conclusion may be limited to those with high graphical literacy. Garcia-Retamero and Galesic (2010) found improvements in understanding with foreground-only graphical displays for participants with both low and high graphical literacy, but that the improvements were greater for those with high graphical literacy. Similar to Garcia-Retamero and Galesic (2010), Gaissmaier and colleagues (2012) also included foreground-only and foreground+background graphical displays as well as numerical displays. Although because of their research interests, Gaissmaier and colleagues (2012) did not test for display differences depending on whether the background was included in the graphical display, an examination of their Figure 2 shows that the foreground-only graphical display increased understanding in relation to a purely numerical display for high graphical literacy participants but decreased understanding for low graphical literacy participants.

²Note that we are using the term relative risk to indicate the relative magnitude of two or more risky events to one particular person. Others (e.g., Woloshin et al., 1999) have distinguished one person's absolute risk from that person's relative risk in comparison with other people regarding the particular risky event. Although both types of relative risk are important, the scenarios we examine assume that we only have general risk statistics, not ones tailored to a particular individual. Thus, the present article focuses solely on the first type of relative risk.

³This procedure of dichotomizing a skewed measure of numeracy and related constructs is consistent with the approach typically taken in the literature (e.g., Gaissmaier et al., 2012; Peters et al., 2006). However, it has the disadvantage of reducing the power of the analysis by treating 0, 1, and 2 correct as being equivalent. Thus, to provide an additional test of whether the participants’ numeracy levels moderated any of our effects, we conducted regression analyses in which we regressed each of our aggregated measures (overall understanding in Experiment 1; understanding of absolute risk, understanding of relative risk, perceived likelihood, negative affective responses, and risk aversion in Experiment 2) on the same predictor variables entered in the main ANOVAs, but with numeracy and its interactions computed on the continuous (nondichotomized) measure of numeracy. None of the interactions with display format were significant, all ps > .11.

⁴We also developed an additional measure of understanding based on whether participants made decisions that were consistent with their personal values (see Carrigan, Gardner, Conner, & Maule, 2004; Edwards & Elwyn, 1999; O'Connor, 1995), which was assessed after the other five measures of understanding. The results with this measure in both studies were somewhat weaker than with most of the other measures, so we do not discuss it further here. However, we encourage other researchers to work on developing this type of measure, as high-quality decisions is arguably the best standard for determining whether the conveyed information is fully understood.