Bodily and affective shared self-other representations in vicarious pain responders

Vicarious pain responses represent the ability to mirror the physical pain of others on our own bodies, a phenomenon that has been linked to individual differences in multisensory processing and empathic traits. There is considerable inter-individual variability in the quality of the pain felt and previous research individuated two groups of people, constituting about 30% of the population, that consciously report feeling the physical pain of others on their own bodies. The two groups are distinguished by the quality of the pain felt: one group reports localised and sensorial qualities (S/L group) whilst the other one reports generalised and affective qualities (A/G group). Vicarious pain perception is intrinsically linked to the body and evidence suggests that differences in bodily phenotypes shape the sensorial and/or affective perception of pain. This thesis further investigated both exteroceptive and interoceptive bodily processes which may be linked to the different qualities of vicarious pain experience. The first three studies of this thesis tested the prediction that vicarious pain responders may have greater bodily malleability and a general tendency to treat all other bodies as related to themselves. The central paradigm used in these studies was the rubber hand illusion (RHI), a measure of how much participants are predisposed to feel that an extraneous body part (i.e. a dummy hand) belongs to them. Article I demonstrated that sensory-localised vicarious pain responders (S/L) perform atypically on the task and are more susceptible to the illusion in the asynchronous and light conditions. Article II further explored why the RHI is not disrupted by asynchrony in the S/L group by applying models of Bayesian sensory inference which explain greater susceptibility to RHI illusion through stronger precision of certain sensory modalities (e.g. vision, touch). The Enfacement Illusion (EI) was also employed in this study as a second paradigm in order to further clarify the role of proprioception in bodily awareness. The overall results reconfirmed that S/L responders perceive asynchrony as synchrony, mainly because they rely more on rhythmic expectations and are more susceptible to proprioceptive imprecision. Article III further addressed the tendency of vicarious pain responders to identify with others, but this time at a social-cognitive level. It employed a series of empathy questionnaires and a self-other association task. The results of vicarious pain responders were comparable to controls on most measures. There were no differences in the social self-other association task and neither on other measures of cognitive empathy such as perspective taking or social skills. Notably, both sensory and affective aspects of vicarious pain were associated with higher emotional contagion and reactivity but not with higher levels of personal distress suggesting that they may have better emotional regulation. Article IV further investigated the results of Article III by recording physiological reactivity including skin conductance, blood pressure and heart rate variability (HRV) (a measure of emotion regulation) in vicarious pain responders as well as interoceptive processing. The findings showed that the affective-general responders have lower interoceptive accuracy whilst the sensory-localised responders have higher emotion regulation. They provided evidence for differences in interoceptive accuracy and emotion regulation which distinguished between the sensory and affective groups. Taken together, the findings of this thesis further characterise bodily and self-other processes in vicarious pain responders and provide substantial evidence for differences in the exteroceptive domain associated with the sensory quality of vicarious pain and differences in the interoceptive domain associated with the affective quality of pain.