Posting environmental risk: Communicating with numerical and nonnumerical messaging across information modalities

Risk communicators frequently engage members of the public through social media; therefore, it is important to understand how to effectively communicate risks about environmental and health issues. This experiment with U.S. adults (N = 737) explored how message features in risk-focused social media posts-namely, message modality (text-only posts or text with the inclusion of photographs or data presentations) and risk representation (numerical risk details or nonnumerical summaries of risk information)-influence risk perceptions, perceived message informativeness, and intentions to share the content. To do so, we drew from research on visual communication and research on numerical and nonnumerical representations of risk. We assessed the robustness of these effects across three environmental risk domains (asthma, heat waves, and vector-borne diseases). We found that compared to text-only messages, text with a data presentation (i.e., graph or table) led to enhanced risk perceptions, perceptions of informativeness, and sharing intentions. Relative to nonnumerical messages, numerical messages generated greater perceived risk, were rated as more informative, and elicited greater sharing intentions. Additionally, the effects of risk representation depended on participants' numeracy level, such that numerical messages (vs. nonnumerical) elicited greater sharing intentions and perceived informativeness among high-numeracy individuals but had no such effects for low-numeracy individuals. We also found some evidence that message effects on perceived informativeness differed based on risk topic. Our results suggest that communicators can consider designing social media risk messages with numerical details and data visualizations.