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The dark side of false beliefs: how they can affect patient’s decisions

A recent study performed in collaboration between the University of Deusto (Spain) and the UNSW Australia shows that people who falsely believe that a bogus drug works find it harder to accept the evidence that a truly effective medication is beneficial.

The research, which is published in the British Journal of Psychology, could have implications for how people make medical decisions in real life, such as whether to get their children vaccinated. The authors were interested about the possibility that promotion of ineffective, pseudoscientific therapies could make people less likely to believe that proven treatments work, which could make people reject the use of conventional medicine, sometimes with serious consequences. Humans are prone to developing false beliefs, particularly about the causes of events – for example, often thinking that their own abilities determine success in tasks when the outcome is really just a matter of chance. While false beliefs can have psychological benefits, such as giving people a sense of control over life, they are not without risk. In the first phase of the study of 147 people the researchers induced half of the participants to develop a strong false belief that a medication could effectively treat a fictitious disease. They did this by showing all participants 100 scenarios where the drug was or wasn’t taken by a patient, and the patient did or didn’t get better. The chance of recovery was the same, with or without the drug, but the 50 per cent of participants who were shown the drug more frequently developed a stronger belief that it was effective. In the second phase of the study, participants were shown another 100 scenarios where the bogus drug was combined with one that did cause the fictitious patient to get better. The main result of the study is that participants who held the strong false belief about the bogus drug had more difficulties learning that the added drug was effective. A consequence of these results, as outlined by the authors, is that people who live in an area or country where pseudoscientific therapy consumption for a disease is high can develop the false belief that pseudoscientific therapy is effective. Thus, this illusion could interfere with the acquisition of evidence-based knowledge about the effectiveness of scientific medicine. Researchers from the University of Deusto in Bilbao in Spain Dr. Ion Yarritu and Professor Helena Matute, and Dr. David Luque from the UNSW Australia and the Univeristy of Málaga (Spain) are the authors of the study. Source (1) Yarritu, 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. Advance Online Publication. DOI: 10.1111/bjop.12119 Further information at:


Australia, Spain