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How Numeracy Influences Risk Comprehension and Medical Decision Making

Department of Human Development, Cornell University, B44 Martha Van Rensselaer Hall, Ithaca, NY 14853, USA.
Psychological Bulletin (Impact Factor: 14.39). 11/2009; 135(6):943-73. DOI: 10.1037/a0017327
Source: PubMed

ABSTRACT We review the growing literature on health numeracy, the ability to understand and use numerical information, and its relation to cognition, health behaviors, and medical outcomes. Despite the surfeit of health information from commercial and noncommercial sources, national and international surveys show that many people lack basic numerical skills that are essential to maintain their health and make informed medical decisions. Low numeracy distorts perceptions of risks and benefits of screening, reduces medication compliance, impedes access to treatments, impairs risk communication (limiting prevention efforts among the most vulnerable), and, based on the scant research conducted on outcomes, appears to adversely affect medical outcomes. Low numeracy is also associated with greater susceptibility to extraneous factors (i.e., factors that do not change the objective numerical information). That is, low numeracy increases susceptibility to effects of mood or how information is presented (e.g., as frequencies vs. percentages) and to biases in judgment and decision making (e.g., framing and ratio bias effects). Much of this research is not grounded in empirically supported theories of numeracy or mathematical cognition, which are crucial for designing evidence-based policies and interventions that are effective in reducing risk and improving medical decision making. To address this gap, we outline four theoretical approaches (psychophysical, computational, standard dual-process, and fuzzy trace theory), review their implications for numeracy, and point to avenues for future research.

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    • "A linear representation would instead treat larger objective differences in outcomes, say between 290 000 and 270 000 lives, as larger psychologically than smaller objective differences, say between 10 000 and 5000 lives. Hence, characterizing high numeracy psychophysically in terms of linearity is at odds with characterizing high numeracy in terms of performance on standard health numeracy tests (which seem to assess a tendency to engage in ratio-dependent, nonlinear comparisons of numbers; Peters et al., 2008; Reyna et al., 2009). "
    Numerical Reasoning in Judgments and Decision Making about Health, Edited by B. L. Anderson, J. Schulkin, 01/2015: chapter 10: pages 215-251; Cambridge University Press., ISBN: 1107040949
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    • "Rather, an individual's level of numeracy seems to be of importance for judgments and decisions in general. For example, people low on numeracy are more sensitive to framing effects (Peters, V€ astfj€ all, Slovic, Mertz, Mazzocco & Dickert, 2006; Reyna et al., 2009), give less accurate estimates of risk (Black, Nease & Tosteson, 1995), and tend to ignore sample size information to a larger extent (Obrecht, Chapman & Gelman, 2009) than people with high numeracy. These findings suggest that numeracy is an important part of everyday judgment and "
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    ABSTRACT: Recent research has highlighted the importance of considering an individual's level of numeracy, that is their numerical abilities, in a vast variety of judgment and decision making tasks. To accurately evaluate the influence of numeracy requires good and valid measures of the construct. In the present study we validate a Swedish version of the Berlin Numeracy Test (Cokely, Galesic, Schulz, Ghazal & Garcia-Retamero, 2012). The validation was carried out on both a student sample and a sample representative of the Swedish population. The Swedish BNT showed sound psychometrical properties in both samples. Further, in both samples the BNT had satisfactory convergent and discriminant validity when correlating with other measures of numeracy, while not being significantly related to measures of personality. With respect to predictive validity the results indicated divergent patterns in the two samples. In the student sample, participants scoring highest on the BNT outperformed those in the other three levels, which did not differ in performance. In contrast, in the population sample participants scoring lowest on the BNT performed worse than those in the other three levels, which did not differ in performance. Taken together, however, the results suggest that the Swedish version of the BNT should be considered a valid measure of numeracy in both Swedish student and population representative samples.
    Scandinavian Journal of Psychology 12/2014; 56(2). DOI:10.1111/sjop.12189 · 1.29 Impact Factor
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    • "The ability to understand and process numeric information, summarized in the concept of Numeracy (Paulos, 1988; in analogy with literacy), has recently attracted interest in research on decision-making (Reyna and Brainerd, 2007; Peters and Levin, 2008; Peters et al., 2008; Reyna et al., 2009). Although no consensus can be found on how numeracy should be defined (see Reyna et al., 2009 for a review) it often refers to an understanding of, and an ability to process, numerical concepts, particularly to comprehend risk and to transform probabilities (Lipkus et al., 2001). A remarkable proportion of even highly educated people apparently lack knowledge of basic numeric concepts (Lipkus et al., 2001). "
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    ABSTRACT: The purpose of the study was to investigate how numeracy and acuity of the approximate number system (ANS) relate to the calibration and coherence of probability judgments. Based on the literature on number cognition, a first hypothesis was that those with lower numeracy would maintain a less linear use of the probability scale, contributing to overconfidence and nonlinear calibration curves. A second hypothesis was that also poorer acuity of the ANS would be associated with overconfidence and non-linearity. A third hypothesis, in line with dual-systems theory (e.g., Kahneman and Frederick, 2002) was that people higher in numeracy should have better access to the normative probability rules, allowing them to decrease the rate of conjunction fallacies. Data from 213 participants sampled from the Swedish population showed that: (i) in line with the first hypothesis, overconfidence and the linearity of the calibration curves were related to numeracy, where people higher in numeracy were well calibrated with zero overconfidence. (ii) ANS was not associated with overconfidence and non-linearity, disconfirming the second hypothesis. (iii) The rate of conjunction fallacies was slightly, but to a statistically significant degree decreased by numeracy, but still high at all numeracy levels. An unexpected finding was that participants with better ANS acuity gave more realistic estimates of their performance relative to others.
    Frontiers in Psychology 08/2014; DOI:10.3389/fpsyg.2014.00851 · 2.80 Impact Factor