Context-dependent placebo hypoalgesia through observational learning: the role of empathy in immersive and non-immersive environments

Digital environments are increasingly used to study social and pain-related behaviors. Empathy and contextual factors influence observationally induced placebo analgesia. We tested whether state empathy (i.e., immediate affective and cognitive responses to another's experience) differs when observing a demonstrator in immersive VR versus 2D video, and whether this modulation affects placebo hypoalgesia. Forty-seven participants observed a human or avatar demonstrator receiving painful stimulation with or without placebo, then experienced the same stimulations. Observation induced significant placebo hypoalgesia for pain intensity and unpleasantness. Human demonstrators evoked greater cognitive empathy, while placebo treatments reduced empathy across contexts. Analgesic effects were stronger in 2D after observing humans, but in VR, avatars induced greater placebo effects. Placebo responsiveness was related to trait empathy in the VR-Human condition; however, state empathy did not mediate the effect. Our findings highlight that demonstrator characteristics and immersion critically shape the social transfer of placebo effects.