SoTact: A socio-tactile picture database for vicarious touch perception studies

Vicarious forms of social touch perception include the experience of touch as a third-party observer. Touch observation plays a pivotal role in social cognition, as tactile interactions convey emotional and social information essential for interpersonal understanding. However, research in this domain is hindered by the scarcity of standardised databases and the heterogeneity of experimental controls. To address these limitations, we developed the Socio-Tactile Picture database, which includes positive tactile gestures (Social Touch), along with two control conditions: a Social No-Touch condition (to isolate social interaction effects) and a Non-Social Touch condition (to control for human tactile specificity). The novelty in the database resides in the inclusion of stimuli from the three aforementioned conditions, combined with gender balance achieved through three actor dyads.The database was validated via an online experiment, where participants rated stimuli on valence, arousal, and naturalness across two sessions. Results showed that the database presented good intra-subject and inter-actor consistency. Moreover, social touch pictures were consistently rated as positive in valence, as hypothesised. The database is publicly available to support future research on the perception of observed touch, offering a robust tool for experimental investigations.