The Influence of Weight-of-Evidence Messages on (Vaccine) Attitudes: A Sequential Mediation Model

Media coverage of contentious risk issues often features competing claims about whether a risk exists and what scientific evidence shows, and journalists often cover these issues by presenting both sides. However, for topics defined by scientific agreement, balanced coverage erroneously heightens uncertainty about scientific information and the issue itself. In this article, we extend research on combating so-called information and issue uncertainty using weight of evidence, drawing on the discredited autism-vaccine link as a case study. We examine whether people's perceptions of issue uncertainty (about whether a link exists) change before and after they encounter a news message with weight-of-evidence information. We also explore whether message exposure is associated with broader issue judgments, specifically vaccine attitudes. Participants (n = 181) read news articles that included or omitted weight-of-evidence content stating that scientific studies have found no link and that scientists agree that none exists. Postexposure issue uncertainty decreased-in other words, issue certainty increased-from preexposure levels across all conditions. Moreover, weight-of-evidence messages were associated with positive vaccine attitudes indirectly via reduced information uncertainty (i.e., one's belief that scientific opinion and evidence concerning a potential link is unclear) as well as issue uncertainty. We discuss implications for risk communication.