Yarritu Corrales, IonMatute, HelenaLuque Ruiz, David2026-02-132026-02-132015-10-10Yarritu, I., Matute, H., & Luque, D. (2015). The dark side of cognitive illusions: when an illusory belief interferes with the acquisition of evidence-based knowledge. British Journal of Psychology, 106(4), 597-608. https://doi.org/10.1111/BJOP.121190007-126910.1111/BJOP.12119https://hdl.handle.net/20.500.14454/5109Cognitive illusions are often associated with mental health and well-being. However, they are not without risk. This research shows they can interfere with the acquisition of evidence-based knowledge. During the first phase of the experiment, one group of participants was induced to develop a strong illusion that a placebo medicine was effective to treat a fictitious disease, whereas another group was induced to develop a weak illusion. Then, in Phase 2, both groups observed fictitious patients who always took the bogus treatment simultaneously with a second treatment which was effective. Our results showed that the group who developed the strong illusion about the effectiveness of the bogus treatment during Phase 1 had more difficulties in learning during Phase 2 that the added treatment was effective.engjournal article2026-02-132044-8295