Social touch as a third-party observer: how interindividual differences shape touch perception

Social touch is crucial for understanding others and emotional communication. The perception of social touch can be experienced directly on the skin but also vicariously through the observation of touch. However, the pleasantness derived from social touch is not uniform; it is shaped by interindividual differences, including state factors (e.g. depression, loneliness, and anxiety) and traits factors (e.g. anhedonia, touch attitude and experience, and empathy). Despite their relevance, the specific effects of these factors on vicarious social touch perception remain scarce and understudied.To bridge this gap, a behavioural experiment was conducted using the Socio-tactile picture database (SoTact) which includes the target condition: social touch, and two control conditions: social no-touch and non-social touch. Forty-four participants rated the pleasantness of these stimuli while we examined the influence of interindividual differences, assessed via questionnaires.Among state factors, higher anxiety levels predicted reduced pleasantness of social touch stimuli. Conversely, trait factors, specifically anhedonia and touch attitudes, significantly predicted pleasantness ratings for both social touch and social no-touch conditions. Moreover, using a mediation analysis, our study also showed that touch attitudes as a measurement of stable trait can partially explain how state of anxiety modifies touch perception. These findings underscore the critical role of interindividual traits and states in shaping vicarious social touch perception, offering insights for future research on emotion and social cognition.