The effects of inoculation interventions and repetition on perceived truth in younger and older adults

Inoculation interventions aim to improve discernment between true and false information, but their effectiveness with older adults is unknown. It is also unknown whether inoculation interventions are effective when misinformation is repeated, as repetition tends to make information seem truer, a phenomenon known as the illusory truth effect. To evaluate whether inoculation intervention efficacy varies with age and information repetition, in this study older and younger adult participants received either an inoculation treatment, in which they learned about a misinformation technique, or they received no intervention. Participants then completed a social media exposure phase where they saw true news headlines, as well as neutrally-framed and manipulatively-framed false news headlines. Participants rated the perceived truth of repeated and new headlines both immediately and after two weeks. Perceptions of threat and counterarguing, two proposed mediators for inoculation efficacy, were measured during both rating phases. Results revealed an illusory truth effect, such that repeated headlines were rated truer than new headlines. The magnitude of this illusory truth effect was larger for older than younger adults and was larger on the delayed than immediate test. However, the inoculation intervention did not improve discernment between true and false information and did not reduce the magnitude of the illusory truth effect for either age group. Although participants in the inoculation and control groups did not differ in perceived threat or counterarguing, counterarguing was consistently associated with higher discernment between true and false headlines. This suggests that counterarguing is an important factor associated with truth discernment.