Przemysław Bąbel

A modified model of learning mechanisms of placebo effects in pain  

In 2011 Colloca and Miller proposed the learning model of placebo effects. In this model, placebo effects result from expectancies acquired by decoding information from the psychosocial context, including conditioned stimuli, symbolic communication, and observation. Thus, according to the model, classical conditioning, verbal suggestions, and observational learning are means by which placebo effects are induced, but expectancy is the only mechanism of the formation of placebo effects. Although the model is influential, recent findings from our lab, as well as other labs, have challenged it. First, it was found that expectancy may not always be involved in placebo effects induced by classical conditioning and that conditioning may be a distinct mechanism of placebo effects. Second, growing evidence on placebo effects induced by observational learning has been recently integrated into the separate model. Third, operant conditioning has been suggested as a new mechanism of placebo effects, and the first evidence supporting that idea was provided. In this talk, I will summarize the current state of the art in the learning mechanisms of placebo effects and propose a modified model of them.