Effect of prior knowledge on the illusory truth effect and memory and metacognitive processes underlying this illusion

Repeated information typically produces higher truth ratings than novel information. This is called the illusory truth effect. Since this illusion can be obtained with various research materials, the repetition of the information is considered as the driving force of the illusion rather than the content, but whether the effect depends on familiarity or recollection is controversial. The present study aimed to investigate how the novelty of the content may also contribute to this effect through familiarity versus recollection. In a series of three experiments, participants were presented with categorical information about novel pseudowords in an initial phase. Then, they were presented with either congruent or incongruent details about the category of the items. It was hypothesized that if familiarity drives the effect, just the mere repetition should increase truth ratings for all old items. Experiment 1 showed that the mere repetition of some cues from previously studied category statements did not produce the illusory truth effect. In Experiment 2, an additional phase of retrieval practice to teach the categorical information about the pseudowords produced a robust illusory truth effect. The results of Experiment 2 showed that when participants learned new information effectively, they made truth assessments by considering the congruence of the semantic details they remembered with existing statements. Experiment 3 aimed to understand how the time interval affects familiarity and recollection processes within the framework of the current research. Contrary to the results of previous studies, Experiment 3 did not find a pattern in which recollection turned into familiarity over time, but the illusory truth effect persisted over time. The results and future work are discussed in the context of referential theory and the illusory truth effect literature.