Background. People’s treatment decisions are often influenced by anecdotal rather than statistical information. This can lead to patients making decisions based on others’ experiences rather than on evidence-based medicine. Objective. To test whether the use of a quiz or pictograph decreases people’s reliance on anecdotal information. Design. Two cross-sectional survey studies using hypothetical scenarios. Participants read a scenario describing angina and indicated a preference for either bypass surgery or balloon angioplasty. The cure rate of both treatments was presented using prose, a pictograph, a quiz, or a pictograph and quiz combination. Participants read anecdotes from hypothetical patients who described the outcome of their treatment; the number of successful anecdotes was either representative or unrepresentative of the cure rates. Setting and Participants. Prospective jurors at the Philadelphia County Courthouse and travelers at the Detroit-Wayne County Metropolitan Airport. Measurements. Proportion of respondents preferring bypass over balloon angioplasty. Results. In study 1, when statistical information was presented in prose, treatment choices were influenced by anecdotes, with 41% of participants choosing bypass when the anecdotes were representative and only 20% choosing it when the anecdotes were unrepresentative (x2 = 14.40, P < 0.001). When statistics were reinforced with the pictograph and quiz, anecdotes had no significant influence on treatment decisions (38% choosing bypass when anecdotes were representative v. 44% when unrepresentative, x2 = 1.08, P > 0.20). In study 2, the tradeoff quiz did not reduce the impact of the anecdotes (27% v. 28% choosing bypass after receiving or not receiving the quiz, x2 < 1, P > 0.20). However, the pictograph significantly reduced the impact of anecdotes, with 27% choosing bypass after receiving no pictograph and 40% choosing bypass after receiving a pictograph (x2 = 6.44, P < 0.001). Conclusions. Presenting statistical information using a pictograph can reduce the undue influence of anecdotal reasoning on treatment choices.
Ajzen I. Intuitive theories of events and the effects of base-rate information on prediction. J Pers Soc Psychol. 1977;35: 303-314.
2.
Bar-Hillel M. The base-rate fallacy in probability judgements. Acta Pscyhologica. 1980;44: 211-233.
3.
Borgida E, Nisbett R. The differential impact of abstract versus concrete information on decisions. J Appl Soc Psychol. 1977;7: 258-271.
4.
Ginosar Z, Trope Y. The effects of base rates and individuating information on judgments about another person. J Exp Soc Psychol. 1980;16: 228-242.
5.
Kahneman D, Tversky A. On the psychology of prediction. Psychol Rev. 1973;80: 237-251.
6.
Lyon D, Slovic P. Dominance of accuracy information and neglect of base rates in probability estimation. Acta Psychologica. 1976;40: 287-298.
7.
Zukier H, Pepitone A. Social roles and strategies in prediction: some determinants of the use of base-rate information. J Person Soc Psychol. 1984;47: 349-360.
8.
Jenni KE, Loewenstein G. Explaining the “identifiable victim effect.”J Risk Uncertain. 1997;14: 235-237.
9.
Schwartz LM, Woloshin S, Black WC, Welch HG. The role of numeracy in understanding the benefit of screening mammography. Ann Intern Med. 1997;127: 966-972.
10.
Weinstein ND. What does it mean to understand a risk? Evaluating risk comprehension. J Natl Cancer Inst Monogr. 1999;25: 15-20.
11.
Lipkus IM, Samsa G, Rimer BK. General performance on a numeracy scale among highly educated samples. Med Decis Making. 2001;21(1): 37-44.
12.
Yamagishi K. When a 12.86% mortality is more dangerous than 24.14%: implications for risk communication. Appl Cognit Psychol. 1997;11: 495-506.
13.
Hamill R, Wilson T, Nisbett R. Insensitivity to sample bias: generalizing from atypical cases. J Person Soc Psychol. 1980;39: 578-589.
14.
Loewenstein GF, Weber EU, Hsee CK, Welch N. Risk as feelings. Psychol Bull. 2001;127(2): 267-286.
15.
Finucane ML, Alhakami A, Slovic P, Johnson SM. The affect of heuristic judgments of risks and benefits. J Behav Decis Making. 2000;13: 1-17.
16.
Ubel PA, Jepson C, Baron J. The inclusion of patient testimonials in decision aids: effects on treatment choices. Med Decis Making. 2001;21: 60-68.
17.
Feldman-Stewart D, Kocovski N, McConnell BA, et al.Perception of quantitative information for treatment decisions. Med Decis Making. 2000;20: 228-238.
18.
Mazur DJ, Hickam DH. Patient preferences: survival vs quality-of-life considerations. J Gen Intern Med. 1993;8: 374-377.
19.
Mazur DJ, Merz JF. How the manner of presentation of data influences older patients in determining their treatment preferences. J Am Geriatr Soc. 1993;41: 223-228.
20.
Gigerenzer G. The psychology of good judgment: frequency formats and simple algorithms. Med Decis Making. 1996;16: 273-280.
21.
Hoffrage U, Gigerenzer G. Using natural frequencies to improve diagnostic inferences. Acad Med. 1998;73(5): 538-540.
22.
Nisbett R, Ross L. Human Inference: Strategies and Shortcomings of Social Judgment. Englewood Cliffs (NJ): Prentice Hall; 1980.
