Abstract
The repetition-induced truth effect refers to a phenomenon where people rate repeated statements as more likely true than novel statements. In this paper, we document qualitative individual differences in the effect. While the overwhelming majority of participants display the usual positive truth effect, a minority are the opposite—they reliably discount the validity of repeated statements, what we refer to as negative truth effect. We examine eight truth-effect data sets where individual-level data are curated. These sets are composed of 1105 individuals performing 38,904 judgments. Through Bayes factor model comparison, we show that reliable negative truth effects occur in five of the eight data sets. The negative truth effect is informative because it seems unreasonable that the mechanisms mediating the positive truth effect are the same that lead to a discounting of repeated statements’ validity. Moreover, the presence of qualitative differences motivates a different type of analysis of individual differences based on ordinal (i.e., Which sign does the effect have?) rather than metric measures. To our knowledge, this paper reports the first such reliable qualitative differences in a cognitive task.
Highlights
In the usual course of experimental psychology, we often understand phenomena by computing the mean effect
The important questions are what proportion of the population is allergic and what are the separate mechanisms of pain relief and allergic reactions
We show to our surprise that in all the data sets where variation is detectable, there are some people who have a reliably negative truth effect
Summary
In the usual course of experimental psychology, we often understand phenomena by computing the mean effect. We find a surprising result: Across many of the data sets, there is a small proportion of individuals that show a negative truth effect. Individual truth effect estimates from the unconstrained model for all eight data sets are shown in the right columns of Figs.
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