Replication data: Hearing is Believing? Estimating the "Illusion of Truth" Effect in the Context of Mass Conspiracy Theories

In this paper, we show that the propensity to agree with a given conspiracy theory depends conditionally on prior knowledge of that theory. First, we present our argument, drawing from results in psychology regarding the “illusion of truth” effect, which identifies the tendency of individuals to believe information based on exposure to that information alone. Then, we model the determinants of theory awareness, investigating which sub-populations are more likely to demonstrate theory familiarity. Lastly, we assess the conditional effect of familiarity on public opinion. Our results indicate that “hearing” and “believing” are linked: after controlling for salient observables, we find that the “illusion of truth” effect appears to be present in the formation of public opinion on conspiracy theories, but in a heterogeneous manner. In particular, there appear to be distinct mechanisms at work for the few theories that are familiar to more than 50 percent of respondents.