The Barnum effect in complementary medicine

Abstract

Summary The Barnum effect describes the phenomenon that people tend to identify themselves with blatant truisms. It has been postulated that this partly determines our attitudes towards complementary medicine. To test this hypothesis, two questionnaires were sent in succession to German doctors. In the first, they were asked to indicate how valid they thought hair analysis was as a general diagnostic tool. They were also asked to send back a hair specimen and were promised the results of their personal hair analysis in turn. No such analyses were performed, but every participant was supplied with the same fictitious results consisting of sweeping commonplace statements. The participants were then asked (second questionnaire) to indicate to what extent they thought these were applicable to them and to reconsider their judgement on the validity of the diagnostic method. There was a high degree of identification with the truisms offered. However, this did not positively change the judgement on hair analysis. Therefore, this experiment does not provide evidence in support of our initial working hypothesis that the Barnum effect can positively modify the view of doctors on a questionable diagnostic method.