Truth assessment on a global level: How people integrate multiple pieces of repeated and nonrepeated information into perceptions of truth.

People are more likely to judge information as true when it has been encountered before, a prominent phenomenon called the truth effect. While this effect is well-studied for single information pieces, previous research has neglected that people often need to assess the truth of compounds of old and new information (e.g., a social media post containing old and new information). In eight preregistered experiments (N = 1,650), we tested how people integrate multiple pieces of old or new information into judgments of truth. We found that participants' truth judgments were consistent with an averaging rule with stronger weight given to old relative to new information pieces. This weighted averaging rule implies three boundary conditions for the truth effect: First, more pieces of old/new information do not lead to more extreme global perceptions of truth or falsehood. Second, the effect of repetition from one piece of information substantially reduces when other pieces of old or new information are present. Third, one piece of old information has a stronger impact on truth judgments than one piece of new information. We also find that the weighted averaging pattern applies to judgments of familiarity but not to judgments of processing fluency. Further, it influences socially relevant judgments like the perceived trustworthiness of the information source. Our framework and findings shed new light on how repetition may influence the perception of truth in more realistic environments that often present a mix of old and new information. (PsycInfo Database Record (c) 2025 APA, all rights reserved).