Health-related myths spread rapidly and can have a negative impact not only on individuals, but also on public health. In the present research, we aim to investigate the extent to which the effectiveness of debunking health misinformation with the truth sandwich text format depends on the source delivering the correction. Further, we examined whether source trustworthiness and psychological reactance mediate this effect. We conducted two pre-registered experimental studies with samples representative of the German population in terms of gender and age (total N = 2,684). In the context of a hypothetical online information search on the topics of vaccines (Study 1) or nutrition (Study 2), participants' exposure to the corrective information to one of several selected myths and its source (general practitioner vs. health institution vs. company) was varied. The main dependent variable was health myth agreement after debunking. We found that the prevalence of vaccine myths was rather low, which methodologically limited our debunking efforts. For nutrition myths, the debunking was successful, and all sources were able to debunk misinformation, as there was no evidence for differences in their effectiveness. However, we found a significant indirect effect of source on myth agreement after debunking, mediated in serial by source trustworthiness and psychological reactance. This research indicates that the effect of the source in a truth sandwich seems to be less important if the debunking message is carefully formulated. However, the characteristics of the source can still exert an indirect influence on the recipients' response to the message.
Blase et al. (Wed,) studied this question.