Countering vaccine hesitancy through medical expert endorsement.

Scientists and medical experts are among the professionals trusted the most. Are they also the most suitable figures to convince the general public to get vaccinated? In a pre-registered experiment, we tested whether expert endorsement increases the effectiveness of debunking messages about COVID-19 vaccines. We monitored a sample of 2,277 people in Italy through a longitudinal study along the salient phases of the vaccination campaign. Participants received a series of messages endorsed by either medical researchers (experimental group) or by generic others (control). In order to minimise demand effects, we collected participants' responses always at ten days from the last debunking message. Whereas we did not find an increase in vaccination behaviour, we found that participants in the experimental group displayed higher intention to vaccinate, as well as more positive beliefs about the protectiveness of vaccines. The more debunking messages the participants received, the greater the increase in vaccination intention in the experimental group compared to control. This suggests that multiple exposure is critical for the effectiveness of expert-endorsed debunking messages. In addition, these effects are significant regardless of participants' trust toward science. Our results suggest that scientist and medical experts are not simply a generally trustworthy category but also a well suited messenger in contrasting disinformation during vaccination campaigns.

Lateral reading and monetary incentives to spot disinformation about science.

Disinformation about science can impose enormous economic and public health burdens. A recently proposed strategy to help online users recognise false content is to follow the techniques of professional fact checkers, such as looking for information on other websites (lateral reading) and looking beyond the first results suggested by search engines (click restraint). In two preregistered online experiments (N = 5387), we simulated a social media environment and tested two interventions, one in the form of a pop-up meant to advise participants to follow such techniques, the other based on monetary incentives. We measured participants' ability to identify whether information was scientifically valid or invalid. Analysis of participants' search style reveals that both monetary incentives and pop-up increased the use of fact-checking strategies. Monetary incentives were overall effective in increasing accuracy, whereas the pop-up worked when the source of information was unknown. Pop-up and incentives, when used together, produced a cumulative effect on accuracy. We suggest that monetary incentives enhance content relevance, and could be combined with fact-checking techniques to counteract disinformation.