Enhanced self-reported affect and prosocial behaviour without differential physiological responses in mirror-sensory synesthesia

Abstract

Mirror-sensory synesthetes mirror the pain or touch that they observe in other people on their own bodies. This type of synesthesia has been associated with enhanced empathy. We investigated whether the enhanced empathy of people with mirror-sensory synesthesia influences experience of situations involving touch or pain, and whether it affects their prosocial decision making. Mirror-sensory synesthetes (N=18, all female), verified with a touch-interference paradigm, were compared to a similar number of age-matched control individuals (all female). Participants viewed arousing images depicting pain or touch; we recorded subjective valence and arousal ratings, and physiological responses, hypothesizing more extreme reactions in synesthetes. The subjective impact of positive and negative images was stronger in synesthetes than in control participants; the stronger the reported synesthesia, the more extreme the picture ratings. However, there was no evidence for differential physiological or hormonal responses to arousing pictures. Prosocial decision making was assessed with an economic game assessing altruism, in which participants had to divide money between themselves and a second player. Mirror-sensory synesthetes donated more money than non-synesthetes, showing enhanced prosocial behaviour, and also scored higher on the Interpersonal Reactivity Index as a measure of empathy. Our study demonstrates the subjective impact of mirror-sensory synesthesia and its stimulating influence on prosocial behaviour.

The validated touch-video database

“…These findings align with prior research indicating that women tend to display stronger vicarious responses to observed pain (Grice-Jackson et al, 2017;Singer et al, 2006a;Ward and Li, 2022;Yang et al, 2009), with a lack of such a bias for reported (neutral) vicarious touch (Ward et al, 2018;Ward and Li, 2022). Future research could use this video database to delve into the relationship between perceived pain or touch in others and mirrored pain or touch in the observer (see for example Ioumpa et al, 2019), with a specific focus on examining potential gender differences. Nevertheless, it is crucial to exercise caution when interpreting these gender-related findings.…”

Characteristics of vicarious touch reports in a general population

“…Moreover, mirror-touch synaesthetes display more pronounced differentiation in their responses when observing touch applied to humans, including human-like objects, compared to non-synaesthetes (Holle et al, 2011;Ward et al, 2018). This suggests a potential link between vicarious touch experiences and heightened empathetic responses toward the recipient of the touch, supported by research showing increased social abilities in this group (Banissy et al, 2011;Banissy and Ward, 2007;Goller et al, 2013;Ioumpa et al, 2019;Maister et al, 2013;Martin et al, 2017;Santiesteban et al, 2015;Ward et al, 2018). While mirrortouch synaesthesia may involve distinct processes beyond shared affective or emotional states (Ward et al, 2018), categorical differences remain debated (Fitzgibbon et al, 2012;Rothen and Meier, 2013;Ward, 2019).…”

“…While existing literature has provided valuable insights, it has often directed its focus towards a specific group known as 'mirror-touch synesthetes'. This small subset of individuals reportedly experiences vicarious sensations in a manner distinct from the broader population (Holle et al, 2011;Ioumpa et al, 2019;Li et al, 2022;Medina and DePasquale, 2017;Ward et al, 2018;Ward and Li, 2022). The aim of our exploratory study was to investigate the characteristics of reported vicarious sensations in a large sample of naïve undergraduate students.…”

“…Additionally, mirror-touch synaesthetes rate emotional stimuli more strongly, possibly suggesting increased sensitivity to emotionally arousing events (Ioumpa et al, 2019).…”