Purpose: Over the past 10 years, numerous research studies have demonstrated that icon arrays (also called "pictographs") are an effective method of communicating risk statistics, especially to less numerate and less graphically literate people. Yet almost no research has studied which icons should be used in these arrays. We sought to assess whether icon type affects perceived likelihood, risk recall, and/or preferences.
Methods: We surveyed 1504 people age 35 to 75 from an online panel and had them complete a cardiovascular risk calculator based on Framingham data using their actual age, weight, and other health data. Participants received their risk calculator output in an icon array (as well as numerical form). Icon type was randomly varied between participants from among 6 types: large rectangular blocks (often used in past research), filled ovals, male/female bathroom icons (gender matched to participant), smiley/frowny faces, a head and shoulders grey outline figure, or actual head and shoulder photographs. In this last condition, the photographs showed multiple faces of people of different races (gender matched). Events were shown by blue versus grey icons (blue vs. grey shirt color in the photo condition). We then measured perceived likelihood, perceived risk magnitude, gist recall, and preferences regarding the icon arrays. In addition, we assessed both subjective numeracy and an abbreviated form of graphical literacy.
Results: Correlations between participants’ perceived likelihood of heart disease or stroke and the displayed risk information varied from a high of 0.30 for ovals to a low of 0.10 for grey outline figures. Similar patterns were observed for perceived risk magnitude. When controlling for risk level, numeracy, and graphical literacy, gist recall was significantly higher when respondents viewed person-like icons (bathroom icons (p<0.01), outline figures (p<0.06), or photos (p<0.02)) versus blocks. Participants who viewed bathroom icons and photos gave higher graph preference ratings than participants viewing blocks.
Conclusions: Icon type can significantly alter people’s responses to risk information presented in pictographs. While person-like icons resulted in better recall and generally higher preference ratings, ovals resulted in higher correlations between perceived likelihood and the presented risk information. More research is clearly needed before definitive guidance can be provided to risk communicators and decision aid developers regarding which icons are most effective.