<Tese de Doutoramento> em <Psicologia>, na especialidade de <Psicologia Cognitiva> apresentada ao Instituto Superior de Psicologia Aplicada, sob a orientação do(a) Prof(ª). Dr(a). <Teresa Garcia-Marques>

ABSTRACT:Repetition seems to increase the truth-value of information, generating the illusion thatrepeated statements are more valid than things we never heard or read before ? the illusion oftruth 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 falseon repetition. We review the literature evidencing repetition?s impact on judgments of truthand the major cognitive mechanisms that have been proposed to explain it. The first studiesinvestigating the mechanisms underlying the effect show that subjective familiarity is moreimportant than actual frequency of exposure. These approaches further suggested that theautomatic memory component of Familiarity has a rather involuntary impact in truthjudgments, and is the one supporting illusions of truth when the controlled Recollectionprocess is impaired. A next approach showed that processing fluency experiences promotedby factors unrelated to previous exposure and memory are sufficient to generate illusions oftruth. The first accounts suggesting processing fluency to be the process underlying the trutheffect maintained the idea that the feelings of familiarity mediate fluency effects on judgedtruth. However, a more recent approach argues that fluency is an ecologically valid cue fortruth, and thus fluency per se directly influences truth judgments, with no need for memoryattributions. Drawing from this previous body of knowledge, we pose the question of whetherthere is something special in the relation repetition has with truth. Some evidence in theliterature may suggest so, for example, the fact that illusions of truth have a higher magnitudewhen 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, wepresent three independent papers exploring the differences that may exist between repetitionand other factors also able to impact truth judgments, and the relevance that repetition?sunique characteristics may have in the shaping of the truth effect. In the first paper wedemonstrate that the association of repetition with truth is more difficult to reverse than whenpure perceptual fluency (e.g., color contrast) is manipulated, and that the confounds betweenthe processing experiences and resulting effects on truth judgments the two variables promotecan be dissociated. In the second and third papers, we isolate the conceptual and perceptualcomponents involved in repetition, showing that conceptual overlap (a match in the contentand meaning) takes precedence over the sharing of perceptual features in the generation ofillusions of truth. Only when individuals no longer can access the specific meaning of whatwas previously presented do perceptual fluency effects emerge. We discuss how our findingsintegrate and expand what was previously known about judgments of truth, addressing thecontributions and clarifications they bring to the main cognitive mechanisms that have beenproposed to explain the effect.