Papers of the Week

The aim of this study was to investigate the effect on observationally acquired placebo analgesia of a model's self-confidence as well as the observer's self-esteem and self-efficacy. In addition, we aimed to verify the stability of the placebo effect induced by observational learning. Participants (N = 60) were randomly assigned to one of three groups: a self-confident model, an unself-confident model, and a control group. In the experimental groups, participants watched a videotaped model who rated the intensity of electrocutaneous pain stimuli applied in the placebo condition as lower than those applied in the non-placebo condition. The different levels of self-confidence in these groups were manifested in the body posture and facial expressions of the model as well as in specific behavior that accompanied the assessment of pain. Then, 16 electrocutaneous pain stimuli of the same intensity, preceded by the placebo or non-placebo, were applied to participants. In both experimental groups, in contrast to the control group, participants experienced less pain in the placebo than in the non-placebo condition. Although the magnitude of placebo analgesia did not differ between the experimental groups, multiple regression analysis revealed that the perceived self-confidence of the model, but not the self-efficacy or self-esteem of the observer, was a significant predictor of the placebo effect. Moreover, placebo analgesia induced by observational learning did not extinguish over the course of the experiment. These results support the premise that the observers' perception of a model's self-confidence plays a significant role in placebo effects. PERSPECTIVE: The results of this study open the discussion on the role of model's features in the effectiveness of observational learning in the induction of placebo effects. The study provides the very first suggestion that the perceived self-confidence of the model may be related to the magnitude of the observationally induced placebo analgesia. It suggests that self-confidence of other patients and medical staff might affect individual pain experiences.