The role of observational learning in the formation of placebo and nocebo effects

Placebo and nocebo effects are learning phenomena that can be induced not only through direct experience (e.g., classical and operant conditioning) or information (e.g., verbal suggestions), but also through indirect experience via observational learning. Observational learning is not only a powerful method for inducing placebo and nocebo effects; it is also a key mechanism that explains how these effects are formed. This chapter summarizes evidence on the effectiveness of observational learning in inducing placebo and nocebo effects across various symptoms and conditions, including pain. The role of three different types of observational learning - behavioral, symbolic, and verbal modeling - in the induction of these effects is discussed. Furthermore, the chapter reviews the psychological mechanisms, such as expectations, and the neural mechanisms that underlie observationally induced placebo effects. Key factors influencing the effectiveness of observational learning are considered, including the characteristics of both the model (e.g., sex, social status, self-confidence, and accuracy) and the observer (e.g., trait empathy). To provide an overview of the current understanding, the social learning model of placebo effects is introduced. Finally, directions for future research and the clinical implications of studies on observational learning in placebo and nocebo effects are explored.