This article reports 4 experiments concerning the effect of repetition on rated truth (the illusorytruth effect). Statements were paired with differentially credible sources (true vs. false). Old trues would be rated true on 2 bases, source recollection and statement familiarity. Oldfalses, however, would be rated false if sources were recollected, leaving the unintentional influence of familiarity as their only basis for being rated true. Even so, falses were rated truer than new statements unless sources were especially memorable. Estimates showed the contributions of the 2 influences to be independent; the intentional influence of recollection was reduced if control was impaired, but the unintentional influence of familiarity remained constant.The truth of any proposition has nothing to do with its credibility and vice versa.-Parker's law of political statements (Bloch, 1979, p. 84) Our interest in this article is with the cognitive processes that influence ratings of probable truth. Ideally, a statement should not be accepted as true without factual evidence in support of its claims. However, people often rely on memories for that evidence. It is sensible to base truth ratings on whether expressed facts corroborate or contradict remembered facts. But memory is imperfect, and it is sensible to trust some remembered facts more than others. We propose that there are two independent bases on which remembered facts are given credence when people rate truth. One basis is recollection: A statement will be accepted as true if it corroborates remembered facts that are associated with a known, credible source, and it will be rejected as false if the facts are associated with a discredited source. The other basis is familiarity: A statement will seem true if it expresses facts that feel familiar. We propose, furthermore, that these two bases differ in the extent to which their influence is controlled rather than automatic. Recollection of source is a controlled use of memory, and its influence on rated truth is intentional. In contrast, increased familiarity is an automatic consequence of exposure, and its influence on rated truth is unintentional.This research was funded by Operating Grant OGP0008122 from the Natural Sciences and Engineering Research Council of Canada; a certificate of approval from the McMaster Ethics Committee is on file. Part of the research was conducted as an honors thesis by Suzanne Farinacci, who was supervised by Ian Maynard Begg.We are grateful for the advice and discussion from our McMaster colleagues, including Marcia Barnes, Lee Brooks, Vincenza Gruppuso, Larry Jacoby, Janine Jennings, Steve Lindsay, Douglas Needham, Rohan Robertson, James Taylor, Jeff Toth, and Andy Yonelinas. We also thank Colleen Kelley of Macalester College for her counsel. Special thanks are due to Jim Anas for being a male voice on the tapes.Correspondence concerning this article should be addressed to Ian Maynard Begg, Department of Psychology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.Our thesis is ...