Using icon arrays to communicate medical risks: overcoming low numeracy.

OBJECTIVE Icon arrays have been suggested as a potentially promising format for communicating risks to patients-especially those with low numeracy skills-but experimental studies are lacking. This study investigates whether icon arrays increase accuracy of understanding medical risks, and whether they affect perceived seriousness of risks and helpfulness of treatments. DESIGN Two experiments were conducted on samples of older adults (n = 59, 62 to 77 years of age) and university students (n = 112, 26 to 35 years of age). MAIN OUTCOME MEASURES Accuracy of understanding risk reduction; perceived seriousness of risks; perceived helpfulness of treatments. RESULTS Icon arrays increased accuracy of both low- and high-numeracy people, even when transparent numerical representations were used. Risks presented via icon arrays were perceived as less serious than those presented numerically. With larger icon arrays (1,000 instead of 100 icons) risks were perceived more serious, and risk reduction larger. CONCLUSIONS Icon arrays are a promising way of communicating medical risks to a wide range of patient groups, including older adults with lower numeracy skills.