Does protection come at a cost? A random stimuli approach to investigating the (side-)effects of misinformation inoculations

Inoculation – an intervention aimed at informing people of the threat of misinformation and the strategies used to spread it – is an increasingly popular approach for fighting fake news. While studies have shown inoculation to be effective in reducing the credibility of fake news, the evidence on whether it might also lead to undesirable side-effects, such as reduced credibility of true news, is mixed. Further, existing research has only rarely tested inoculation using real-life news, has not accounted for the potential issue of biased stimulus selection, and has not tested the assumed mechanism behind the inoculation's effectiveness: the higher presence of misinformation strategies in fake vs. true news. The present research was designed to fill these gaps. Using a random stimuli approach and a dataset of real-life true and fake news headlines, Study 1 showed that inoculation decreased perceived accuracy (but not trustworthiness) of fake news (without changing the perceived accuracy of true news), and did not render people more cynical. Additionally, Study 2 showed that fake news contained more misinformation strategies than true news, and Study 3 found that the inoculation worked better on headlines that used more (vs. fewer) misinformation strategies. In sum, our findings suggest that inoculation is unlikely to have side effects, yet its effectiveness might be more limited than previously assumed. We thus contribute to the broader literature on reducing misinformation, and research on the effectiveness of the inoculation approach in particular.