icon array

Why Use Icon Arrays

Twenty years ago, a psychological study compared for the first time rudimentary icon displays for communicating risk. Today, we have dozens of randomized experiments to support the use of icon arrays (sometimes referred to as “pictographs”) as an evidence-based standard in medical risk communication.

Icon arrays use a matrix of icons (usually 100 or 1000 icons) to represent an at-risk population, simultaneously displaying both the number of expected events and the number of expected non-events. As a result, icon arrays have several advantages over simple numerical displays and other types of visual displays.

  1. Icon arrays can be read simply by counting icons. This enables icon arrays to be more precisely read than bar or pie charts. Recent research suggests that counting icons is particularly common among more numerate readers.
  2. Icon arrays show the part-whole relationship clearly in both relative count and relative area, thus embodying one of the advantages of pie charts and providing a significant advantage over bar charts and numerical representations.
  3. Icon arrays are inherently a frequency-based representation of risk. Research by Gigerenzer, Peters and others has shown that many people, especially the less numerate, respond differently to frequency representations of risk than they do to percentages.
  4. The icon arrays generated by Iconarray.com build the icons representing risk events from the bottom upwards by rows. As a result, these icon arrays have a rough height cue as well (displays of larger risks have colored icons rising higher than displays of lower risks), thus mirroring bar graphs in format as well.

UM researchers have published multiple articles demonstrating that icon arrays (“pictographs”) are more effective than bar or pie charts at communicating risk and reducing cognitive biases in risk perceptions. These studies have all presented identical risk information in different visual formats and tested not only people’s understanding of the exact numbers (“verbatim” knowledge) but also their “gist” understanding, since these more conceptual understandings can have significant influence on decision making. For example, earlier research had showed that presenting equal numbers of patient testimonials describing good and bad outcomes could make many people think that these outcomes are equally likely even when risk statistics were provided that stated otherwise. However, we showed that supplementing the risk statistics with a pictograph counteracted this effect.


But we are not alone in recommending icon arrays. Below is an abbreviated bibliography of just some of the research studies that we are aware of that support the use of icon arrays to communicate risk statistics.

  1. Fagerlin A, Wang C, Ubel PA. Reducing the influence of anecdotal reasoning on people’s health care decisions: Is a picture worth a thousand statistics? Med. Decis. Making. 2005;25(4):398–405.
  2. Waters EA, Weinstein ND, Colditz GA, Emmons KM. Reducing aversion to side effects in preventive medical treatment decisions. J. Exp. Psychol. Appl. 2007 Mar;13(1):11–21.
  3. Price M, Cameron R, Butow P. Communicating risk information: the influence of graphical display format on quantitative information perception-Accuracy, comprehension and preferences. Patient Educ. Couns. 2007 Dec;69(1-3):121–8.
  4. Zikmund-Fisher BJ, Fagerlin A, Ubel PA. Improving understanding of adjuvant therapy options by using simpler risk graphics. Cancer. 2008;113(12):3382–90.
  5. Zikmund-Fisher BJ, Ubel PA, Smith DM, Derry HA, McClure JB, Stark A, et al. Communicating side effect risks in a tamoxifen prophylaxis decision aid: The debiasing influence of pictographs. Patient Educ. Couns. 2008;73(2):209–14.
  6. Hawley ST, Zikmund-Fisher BJ, Ubel PA, Jankovic A, Lucas T, Fagerlin A. The impact of the format of graphical presentation on health-related knowledge and treatment choices. Patient Educ. Couns. 2008;73(3):448–55.
  7. Galesic M, Garcia-Retamero R, Gigerenzer G. Using icon arrays to communicate medical risks: overcoming low numeracy. Health Psychol. 2009 Mar;28(2):210–6.
  8. Garcia-Retamero R, Galesic M. Communicating treatment risk reduction to people with low numeracy skills: a cross-cultural comparison. Am. J. Public Health. 2009 Dec;99(12):2196–202.
  9. Zikmund-Fisher BJ, Fagerlin A, Ubel PA. A demonstration of “less can be more” in risk graphics. Med. Decis. Making. 2010;30(6):661–71.
  10. Garcia-Retamero R, Galesic M. Who profits from visual aids: Overcoming challenges in people’s understanding of risks. Soc. Sci. Med. 2010;70(7):1019–25.
  11. Garcia-Retamero R, Dhami MK. Pictures speak louder than numbers: on communicating medical risks to immigrants with limited non-native language proficiency. Health Expect. 2011 Mar;14 Suppl 1:46–57.
  12. Hess R, Visschers VHM, Siegrist M. Risk communication with pictographs: The role of numeracy and graph processing. Judgm. Decis. Mak. 2011;6(3):263–74.
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