Who do we learn pain from? : the influence of the demonstrator’s pain assessment skills on nocebo hyperalgesia induced via observational learning

The study aimed to determine if the pain assessment skills of the individual being observed influence observationally induced placebo effects in pain. Participants were randomly assigned to two experimental groups and one control group. In the experimental groups, participants observed the responses to the placebo of a model who had previously shown either high accuracy (high-accuracy group) or low accuracy (low-accuracy group) in differentiating the intensity of pain stimuli. The model exhibited less pain in response to pain stimuli when a placebo was administered, and more pain when no placebo was given. The control group did not observe anyone experiencing pain during the experiment. All participants then received a series of pain stimuli of the same intensity, half of which were administered with a placebo, and rated the intensity of pain. Pain-related expectations of the participants were also measured. Observational learning caused a form of nocebo hyperalgesia in the participants, leading to a slight increase in response to stimuli applied with a placebo and significant increase in pain in response to stimuli applied without a placebo in participants from the high-accuracy group. Observational learning resulted in pain-related expectations, regardless of the observed model’s accuracy. However, these expectations mediated participants’ responses to pain only in the low-accuracy group. The findings suggest that the pain assessment skills of the observed model play a significant role in shaping observers’ pain-related expectations and their responses to a placebo.