Warning and contextual mechanisms in the illusory truth effect

The illusory truth effect refers to the tendency to judge repeated statements as more credible than novel ones. Although this effect is commonly attributed to processing fluency arising from prior exposure, increasing evidence suggests that non-experiential factors also shape credibility judgments. Here we examined whether two non-experiential factors, explicit warnings and implicit contextual cues, modulate the illusory truth effect. Across three online experiments using a standard truth-by-repetition paradigm, participants rated the credibility of repeated and new statements referring to generally unknown trivial facts. Experiment 1 tested the effect of a warning stating that half of the statements were false. Replicating previous findings, the warning reduced the illusory truth effect by selectively lowering credibility ratings for repeated statements, while leaving judgments of new statements unaffected. Experiment 2 investigated whether credibility judgments are influenced by the informational context in which statements are presented. The critical set of unknown statements was embedded among either blatantly true or blatantly false filler statements, while participants received the same warning. Contrary to predictions, credibility ratings were higher in blatantly true than in blatantly false contexts for both repeated and new statements. Crucially, this contextual effect was replicated in Experiment 3 in the absence of any warning. Together, the findings support a two-mechanism account: warnings increase skepticism at encoding and selectively attenuate repetition-based credibility gains, whereas contextual cues shift credibility judgments more broadly, affecting both repeated and novel statements.