Pain Observation, Empathy, and the Sensorimotor System: Behavioural and Neurophysiological Explorations

Abstract

Previous research has established that observing another in pain activates both affective and sensorimotor cortical activity that is also present during the first-hand experience of pain. Some researchers have taken this “mirroring” response as indicative of empathic processing. However, very little work has explored the downstream behavioral effects of empathic pain observation. The aim of this dissertation is to begin to fill this gap in the literature by exploring the relationship between empathic pain observation, overt motor behaviours, and sensorimotor activity. In chapters 2-4, I provide robust evidence that observing pain inflicted on another person leads to faster reaction time responses. This effect is shown to be temporally extended (by at least 500ms after pain observation), effector-general (affecting both finger and foot responses), influenced by top-down (i.e., instructions to explicitly empathize) but not bottom-up (i.e., the perceived level of pain) factors, and is not influenced by adaptive (approach/withdraw) behaviours. In chapter 5, I show that sensorimotor activity, measured via TMS-induced Motor Evoked Potentials, increases while observing another in pain regardless whether the observer is preparing to make an action vs. passively observing the stimuli. These results run counter to the literature, and I provide several explanations for why these results were found. Lastly, in chapter 6, I show that sensorimotor activity, measured via Mu and Beta suppression, also increases while observing another in pain regardless whether the observer is preparing to make an action vs. passively observing the stimuli. Interestingly, I do not find significant correlations between sensorimotor activity during pain observation and faster reaction times after pain observation. I embed these findings in relation to the wider social neuroscience of empathy literature and discuss several limitations and challenges in empirically measuring “empathy” as a psychological construct. Overall, this dissertation furthers our understanding of empathy for pain by highlighting the behavioural consequences of pain observation and its connection (or rather, lack thereof) to sensorimotor activity during pain observation.