Study 1 is based on the first author's master thesis under the second author's supervision. The authors declare that they have no conflicts of interest. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. All procedures performed in the present study were in accordance with the ethical guidelines specified in the APA Code of Conduct as well as the authors' national ethics guidelines. Preregistration, study material and data are openly accessible on the Open Science Framework (https://osf.io/guqn5/).The authors would like to thank Friederike Dippel for collecting the data of Study 2.

Everyone loves a conspiracy', Dan Brown writes in his world-famous novel The Da Vinci Code (2003: 169), and its sales numbers prove him right (Wyatt, 2005). This observation seems to apply not only to fiction but also to the real world, where conspiracy theories-explanations of past or current phenomena, which accuse a group of powerful individuals of acting in secret to achieve selfish, malevolent goals (Imhoff & Lamberty, 2020b)-are widespread and cover a wide range of topics (e.g., politics,

Written work such as Wikipedia articles can contain hindsight bias. Since reading biased texts can, in turn, increase recipients' individual hindsight bias, it is an important agenda to examine effective debiasing strategies. In the present study (N = 164), we tested whether providing authors with debiasing strategies can effectively reduce hindsight bias in their content. Specifically, participants wrote an article based on several newspaper articles about a dam and we manipulated whether they received event knowledge (i.e., dam collapse) and a debiasing intervention. Ten blind coders rated the extent to which the produced articles were suggestive of the disaster. Debiasing was successful in reducing both author and article hindsight bias when provided before writing. However, it had no effect when applied to encourage a revision process after writing. We thus argue that implementing pre-writing debiasing in the field may be an important way to reduce collective hindsight bias.

All procedures performed in the present study were in accordance with the ethical guidelines specified in the APA Code of Conduct as well as the authors' national ethics guidelines.Preregistrations, study material, data, analysis scripts and supplemental analysis are openly CHARACTERISTICS OF CONSPIRACY THEORIES 2 accessible on the Open Science Framework (https://osf.io/gfas3/). The authors would like to thank Nadine Loutsch for the material acquisition and Jonas Knäble, Jennifer Weyell, Nina Winands, and Felix Zimmer for coding all articles in Study 1.