Numeracy, ratio bias, and denominator neglect in judgments of risk and probability
Learning and Individual Differences, 18 (1):
89--107 (2008)DOI: 10.1016/j.lindif.2007.03.011
Abstract
” Numeracy,” so-called on analogy with literacy, is essential for making health and other social judgments in everyday life Reyna, V. F., & Brainerd, C. J. (in press). The importance of mathematics in health and human judgment: Numeracy, risk communication, and medical decision making. Learning and Individual Differences.. Recent research on numeracy in health decision making has shown that many adults fail to solve simple ratio and decimal problems, concepts that are prerequisites for understanding health-relevant risk communications. In addition, adults exhibit a ratio bias, in which higher frequencies bias probability judgments, and denominator neglect, described by Reyna and Brainerd (e.g., Reyna, V. F. (1991). Class inclusion, the conjunction fallacy, and other cognitive illusions. Developmental Review, 11, 317–336.; Reyna, V. F., & Brainerd, C. J. (1994). The origins of probability judgment: A review of data and theories. In G. Wright & P. Ayton (Eds.), Subjective probability. (pp. 239–272). New York: Wiley.) and independently by Epstein (e.g., Epstein, S. (1994). Integration of the cognitive and psychodynamic unconscious. American Psychologist, 49, 709–724.). Along with research in education and cognitive development, this work demonstrates that adults have difficulty with a broad range of ratio concepts, including fractions, proportions, risks and probabilities. The psychological mechanisms underlying this difficulty are characterized using dual-processes approaches such as fuzzy-trace theory, simple and effective interventions are described that eliminate common problem-solving errors, and implications for the effective use of numerical information in risk communication are discussed.