Consistent with the principles of evidence-based medicine, effectively communicating evidence (including risks) in medicine is an essential part of shared decision making (SDM). SDM has been defined as ‘an approach where clinicians and patients share the best available evidence when faced with the task of making decisions, and where patients are supported to consider options, to achieve informed preferences’.1 This process relies on access and understanding of evidence-based information by both patients and healthcare professionals. This includes outcome probabilities, typically presented numerically. Yet, a considerable fraction of the population is confronted with limited numeracy. Numeracy is defined as the ability to understand, use and interpret numbers and calculations in everyday situations.2 This difficulty processing numbers is a significant barrier to effective communication in healthcare and SDM.

Many studies demonstrate the potential of visuals to facilitate the presentation and understanding of both qualitative and quantitative information, including numbers.3 4 We define visuals broadly, as including pictures and graphical displays used to show or explain something. We define graphical displays as two-dimensional graphical representations showing a risk information, and graph literacy, as the ability to understand information presented graphically.

Our systematic review and meta-analysis of 54 randomised controlled trials comparing visuals and text to text alone (42 in the meta-analysis) suggested that visuals moderately improved knowledge/understanding and information recall, but largely increased knowledge/understanding for people with limited health literacy (n=13).5 Health literacy is defined as the capacity to obtain, process and understand basic health information and services needed to make appropriate health decisions. Our narrative synthesis suggested that visuals with few words may be most helpful in conveying health information. These findings further support the hypothesis of pictorial superiority. Pictorial superiority is defined as the tendency to remember concrete items more easily when presented as pictures rather than …