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

Abstract

Visual displays, such as icon arrays and risk ladders, are often used to communicate numerical health information. Number lines improve reasoning with rational numbers but are seldom used in health contexts. College students solved ratio problems related to COVID-19 (e.g., number of deaths and number of cases) in one of four randomly assigned conditions: icon arrays, risk ladders, number lines, or no accompanying visual display. As predicted, number lines facilitated performance on these problems-the number line condition outperformed the other visual display conditions, which did not perform any better than the no visual display condition. In addition, higher performance on the health-related ratio problems was associated with higher COVID-19 worry for oneself and others, higher perceptions of COVID-19 severity, and higher endorsement of intentions to engage in preventive health behaviors, even when controlling for baseline math skills. These findings have important implications for effectively presenting health statistics. Public Significance StatementIn Fall 2020, college students who had just returned to campus after the COVID-19 shutdown were better able to solve health-related ratio problems (e.g., comparing the number of deaths and number of cases of COVID-19) when they were paired with number lines than when they were paired with other visual displays commonly used to communicate health statistics (i.e., icon arrays and risk ladders). Number lines are seldom used in health contexts but may be a valuable tool for communicating health-related ratios.

Leveraging Math Cognition to Combat Health Innumeracy

“…It is common for people to explicitly mention in their strategy reports that they focused on numerators in isolation (Fazio et al, 2017; Sidney, Thalluri, et al, 2019; Siegler et al, 2011; Siegler & Thompson, 2014; Thompson et al, 2021). People also focused on just numerators early in the COVID-19 pandemic when the news media and politicians claimed that the seasonal flu was more common than COVID-19 because the absolute number of flu deaths was greater than the absolute number of COVID-19 deaths (Mielicki, Fitzsimmons, Schiller, et al, 2022; Netburn, 2020; Scheibe et al, 2022; Thompson, Taber, Sidney, & Coifman, 2020; Thompson et al 2021). This misunderstanding of case-fatality rates likely influenced people’s beliefs that COVID-19 was less of a threat than the seasonal flu.…”

“…Number lines are often present in classrooms because they are a critical part of training children how to reason about the magnitude of numbers and compare those magnitudes to one another (see Common Core State Standards Writing Team, 2011; National Governors Association Center for Best Practices & Council of Chief State School Officers, 2010). Number lines have helped people of all ages more accurately interpret the magnitude of numbers relative to one another and to the endpoints of the line (Fitzsimmons, Woodbury, et al, in press; Mielicki, Fitzsimmons, Schiller, et al 2022; Siegler, 2016; Thompson et al, 2021). 7 According to the integrated theory of whole number and fractions development (Siegler et al, 2011), number lines are a useful tool to show what whole numbers and fractions have in common: magnitudes whose values can be placed on number lines.…”

“…This suggests that the intervention taught participants about the magnitude of the COVID-19 severity relative to the flu. (b) Example visual displays from Mielicki, Fitzsimmons, Schiller, et al (2022). Number lines, risk ladders, and icon arrays are shown from left to right.…”

“…Alerting adults that the natural-number bias exists may prompt them to slow down and “make sense” of a fraction-related math problem (i.e., rely on relational reasoning). This may encourage people to use more effective strategies to translate rational-number information into an easier-to-interpret format (Alibali & Sidney, 2015; Fazio et al, 2017; Fitzsimmons et al, 2020b; Mielicki, Fitzsimmons, Schiller, et al, 2022; Moss & Case, 1999; Sidney, Thalluri, et al, 2019; Siegler et al, 2011; Siegler & Thompson, 2014; Thompson et al, 2021) rather than impulsively calculating (Schiller, 2020) and overapplying natural-number knowledge to fraction problems. Such interventions would help adults with low numeracy overcome their misunderstanding of rational numbers to engage strategically with rational-number magnitudes (see Alibali & Sidney, 2015; Fitzsimmons et al, 2020b; Schiller et al, 2022; see Fig.…”

“…In addition, we propose that our own recent cross-disciplinary efforts have shown promise in integrating theoretical and methodological insights from both math cognition and health decision-making (Choi et al, 2020; Fitzsimmons, Woodbury, et al, in press; Mielicki, Fitzsimmons, Schiller et al, 2022; Scheibe et al, 2022; Thompson et al, 2021; Thompson, Taber, Sidney, et al, 2020). We believe that interdisciplinary, collaborative science that bridges domains has the potential to make the greatest real-world impact (Klein et al, 2017).…”