The effect of communication design and recipients' numeracy on responses to UXO risk

Risk communications aim to affect recipients' understanding of specific risks, their trust and liking of the materials, affective responses, and associated behaviors. We developed communications about the number of construction workers expected to get hurt if building were permitted at the former Fort Ord weapons training site in California, despite its contamination with unexploded ordnance (UXO). We created eight versions, which presented text only or bar graph with text, the numerator of the risk (the number of workers expected to be hurt) with or without emphasis on the denominator (the total number of workers), and uncertainty information (the probability that different numbers of workers would be hurt) or not. Recipients varied in numeracy. We examined the effect of these communication features on recipients' (1) understanding, (2) trust and liking of the materials, (3) affective responses, and (4) support for construction and for construction workers if construction were to be implemented. Low-numerate individuals showed less understanding across all versions of the communication, yet preferred graph-with-text displays relatively more than text-only displays as compared to high-numerate individuals. Emphasizing the denominator increased understanding of text-only displays but decreased support for construction and construction workers for all communication versions. Moreover, recipients were more supportive of construction and construction workers after receiving text-only displays without uncertainty information or graph-with-text displays with uncertainty information, seemingly due to communications with those features being trusted and liked more. We discuss the implications for communicating risks in general and for communicating UXO-related risks to the community surrounding Fort Ord.