Everybody Hurts: Behavioural, autonomic, and neuro-physiological correlates of directly compared socially learnt nocebo hyperalgesia

The current pre-registered study compared subjective, autonomic and neurophysiological correlates of nocebo hyperalgesia across three groups: Direct Experience (N=20), Social Learning (N=20), and Control (N=20). Participants first underwent a Learning-Phase, where an association between treatment cues and painful thermal stimulation was established. Conditioned responses, induced via social or direct experience, were assessed during the Test-Phase, relative to the control comparator. Pain perception, autonomic arousal, and brain activity were measured via VAS, electrodermal activity, facial action units, and electroencephalography. Both direct and social learning produced significant nocebo hyperalgesia, as indicated by increased pain ratings, autonomic arousal, and modulation of event-related potentials. Increased N2 amplitude, associated with nociceptive processing, was comparable across the two conditioned groups, demonstrating expectancy-driven changes in brain activity irrespective of learning type. While social learning elicited stronger nocebo hyperalgesia in subjective ratings, direct experience was associated with heightened autonomic response and greater activation of facial action units associated with pain during the Learning-Phase. Differences in the trajectory of the autonomic response during the Test-Phase was also observed, with phasic responses diminishing for direct experience but persisting social learning. These findings highlight the role of social information in shaping maladaptive pain responses and highlights the need to mitigate nocebo effects in clinical settings where maladaptive health outcomes can be both directly experienced and socially expressed. By demonstrating distinct behavioural and physiological patterns associated with direct and social learning, this research contributes to understanding the mechanisms underlying expectancy-driven pain modulation.