“the Truth Is Never Pure and Rarely Simple”: Understanding the Role of Repetition and Processing Fluency on the Illusion of Truth Effect

Repetition seems to increase the truth-value of information, generating the illusion that repeated statements are more valid than things we never heard or read before – the illusion of truth effect. The present thesis aims at providing further and clearer understanding of “why” and “how” we base the important decision of something we hear being true rather than false on repetition. We review the literature evidencing repetition’s impact on judgments of truth and the major cognitive mechanisms that have been proposed to explain it. The first studies investigating the mechanisms underlying the effect show that subjective familiarity is more important than actual frequency of exposure. These approaches further suggested that the automatic memory component of Familiarity has a rather involuntary impact in truth judgments, and is the one supporting illusions of truth when the controlled Recollection process is impaired. A next approach showed that processing fluency experiences promoted by factors unrelated to previous exposure and memory are sufficient to generate illusions of truth. The first accounts suggesting processing fluency to be the process underlying the truth effect maintained the idea that the feelings of familiarity mediate fluency effects on judged truth. However, a more recent approach argues that fluency is an ecologically valid cue for truth, and thus fluency per se directly influences truth judgments, with no need for memory attributions. Drawing from this previous body of knowledge, we pose the question of whether there is something special in the relation repetition has with truth. Some evidence in the literature may suggest so, for example, the fact that illusions of truth have a higher magnitude when they are induced by repetition than when other fluency sources are used. Additionally, repetition has the unique characteristic of aggregating both perceptual and conceptual fluency, which may add an “extra” layer to the association with truth. Exploring these questions, we present three independent papers exploring the differences that may exist between repetition and other factors also able to impact truth judgments, and the relevance that repetition’s unique characteristics may have in the shaping of the truth effect. In the first paper we demonstrate that the association of repetition with truth is more difficult to reverse than when pure perceptual fluency (e.g., color contrast) is manipulated, and that the confounds between the processing experiences and resulting effects on truth judgments the two variables promote can be dissociated. In the second and third papers, we isolate the conceptual and perceptual components involved in repetition, showing that conceptual overlap (a match in the content and meaning) takes precedence over the sharing of perceptual features in the generation of illusions of truth. Only when individuals no longer can access the specific meaning of what was previously presented do perceptual fluency effects emerge. We discuss how our findings integrate and expand what was previously known about judgments of truth, addressing the contributions and clarifications they bring to the main cognitive mechanisms that have been proposed to explain the effect.