The truth revisited: Bayesian analysis of individual differences in the truth effect

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.

The truth revisited: Bayesian analysis of individual differences in the truth effect

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 8 truth-effect data sets where individual-level data are curated. These sets are composed of 1,105 individuals performing 38,904 judgments. Through Bayes factor model comparison, we show that reliable negative truth effects occur in 5 of the 8 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.

MODELS OF POSITIVE TRUTH

This paper is a follow-up to [4], in which a mistake in [6] (which spread also to [9]) was corrected. We give a strenghtening of the main result on the semantical nonconservativity of the theory of PT−with internal induction for total formulae${(\rm{P}}{{\rm{T}}^ - } + {\rm{INT}}\left( {{\rm{tot}}} \right)$, denoted by PT−in [9]). We show that if to PT−the axiom of internal induction forallarithmetical formulae is added (giving${\rm{P}}{{\rm{T}}^ - } + {\rm{INT}}$), then this theory is semantically stronger than${\rm{P}}{{\rm{T}}^ - } + {\rm{INT}}\left( {{\rm{tot}}} \right)$. In particular the latter is not relatively truth definable (in the sense of [11]) in the former. Last but not least, we provide an axiomatic theory of truth which meets the requirements put forward by Fischer and Horsten in [9]. The truth theory we define is based on Weak Kleene Logic instead of the Strong one.

MODELS OF PT– WITH INTERNAL INDUCTION FOR TOTAL FORMULAE

We show that a typed compositional theory of positive truth with internal induction for total formulae (denoted by PTtot) is not semantically conservative over Peano arithmetic. In addition, we observe that the class of models of PA expandable to models of PTtot contains every recursively saturated model of arithmetic. Our results point to a gap in the philosophical project of describing the use of the truth predicate in model-theoretic contexts.

A Modern Dilemma: Changing Notions of Truth and Expertise in 20th-Century American Medical Science

“Beauty is in the eye of the beholder”: so wrote Duchess, Margaret Wolfe Hungerford. So, too, might we say today, at the 21st century's beginning, and not simply of beauty, or ugliness, or of justice or injustice, or of wisdom or folly, as Ralph Waldo Emerson might have had it a generation before her, but of truth, even scientific truth. The 20th century has not been kind to many 19th-century notions, ideals, and practices. Among those it has treated the most harshly is that of objective, scientific truth. In Hungerford's day, most educated people in the Western world spoke and acted as if truth was attainable. Positive truth was available to those trained in the special knowledge and methods of the professional expert. In Western Europe and North America, the educated classes regarded such special knowledge — expertise, that is — the natural and inevitable consequence of academic and scientific institutions there. And the professionalization of American science, thanks to the faculty of American private and public graduate universities in the half-century following 1870, set the intellectual and ideological horizons of science, scholarship, and the professions. The professional ideal crystallized, with its concomitant notions of the expert with special training and knowledge and a desire to serve the general public, not greedy commercial interests. Truth was not diluted. For the professionals and their client populations, it was absolute, unchanging, timeless. The professional scientist could verify it with his expert methods.