The Feature Positive Effect Biases Vaccination Information Processing

Evidence-based vaccination communication aims to support people in making informed decisions regarding vaccination. It is therefore important to learn how vaccination information is processed and how it might be biased. One potentially relevant bias that is overlooked in the vaccination literature is the feature positive effect (FPE), the phenomenon that people experience greater difficulty processing nonoccurring events than occurring events, which impacts judgment and decision making. The present study adopts an experimental design with sequential testing rules to examine a potential FPE for vaccination information processing. The results convincingly demonstrate that vaccination-related events described as nonoccurring (e.g., no side effects after vaccination) versus occurring (e.g., side effects after vaccination) indeed result in lower recall and are perceived as less important in evaluating the vaccine. The results regarding processing time remain inconclusive. These findings might help explain the appeal of vaccination-critical information and suggest that emphasizing what does happen as a result of vaccination, rather than what does not, can help debias the processing of evidence-based vaccination information.