At the onset of the coronavirus disease (COVID-19) global pandemic, our interdisciplinary team hypothesized that a mathematical misconception—whole number bias (WNB)—contributed to beliefs that COVID-19 was less fatal than the flu. We created a brief online educational intervention for adults, leveraging evidence-based cognitive science research, to promote accurate understanding of rational numbers related to COVID-19. Participants from a Qualtrics panel (N = 1,297; 75% White) were randomly assigned to an intervention or control condition, solved health-related math problems, and subsequently completed 10 days of daily diaries in which health cognitions and affect were assessed. Participants who engaged with the intervention, relative to those in the control condition, were more accurate and less likely to explicitly mention WNB errors in their strategy reports as they solved COVID-19-related math problems. Math anxiety was positively associated with risk perceptions, worry, and negative affect immediately after the intervention and across the daily diaries. These results extend the benefits of worked examples in a practically relevant domain. Ameliorating WNB errors could not only help people think more accurately about COVID-19 statistics expressed as rational numbers, but also about novel future health crises, or any other context that involves information expressed as rational numbers.

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At the onset of the COVID-19 global pandemic, our interdisciplinary team hypothesized that a mathematical misconception--whole number bias (WNB)--contributed to incorrect beliefs that COVID-19 was less fatal than the flu. We created a novel, five-minute online educational intervention, leveraging evidence-based cognitive science research, to encourage accurate COVID-19 and flu fatality rate calculations and comparisons. As predicted, adults (N = 1,297) randomly assigned to the intervention were more likely to correctly answer health decision-making problems and were less likely to report WNB errors in their problem-solving strategies relative to control participants. There were no immediate effects of condition on COVID-19 risk perceptions and worry; however, those in the intervention group did exhibit increased perceived risk and worry across 10 days of daily diaries. The intervention did not cause distress; instead, it increased positive affect. Ameliorating WNB errors could impact people’s risk perceptions about future health crises.

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.

Children display an early sensitivity to implicit proportions (e.g., 1 of 5 apples vs. 3 of 4 apples), but have considerable difficulty in learning the explicit, symbolic proportions denoted by fractions (e.g., “1/5” vs. “3/4”). Theoretically, reducing the gap between representations of implicit versus explicit proportions would improve understanding of fractions, but little is known about how the representations develop and interact with one another. To address this, we asked 177 third, fourth, and fifth graders (M = 9.85 years, 87 girls, 69% White, 19% low income) to estimate the position of proportionally equivalent integers and fractions on number lines (e.g., 3 on a 0–8 number line vs. 3/8 on a 0–1 number line, Study 1). With increasing age, children’s estimates of implicit and explicit proportions became more coherent, such that a child’s estimates of fractions on a 0–1 number-line was a linear function of the same child’s estimates of equivalent integers. To further investigate whether preexisting integer knowledge can facilitate fraction learning through analogy, we assigned 100 third to fifth graders (M = 10.04 years, 55 girls, 76% White) to an Alignment condition, where children estimated fractions and integers on aligned number lines, or to a No Alignment condition (Study 2). Results showed that aligning integers and fractions on number lines facilitated a better understanding of fractional magnitudes, and increased children’s fraction estimation accuracy to the level of college students’. Together, findings suggest that analogies can play an important role in building a coherent understanding of proportions.