The roles of synchronous visuo-tactile and visuo-motor stimulations in self-location during whole-body embodiment: an exploratory study

The human sense of self is plastic and can be modulated by multisensory and sensorimotor coupling in immersive virtual reality. In particular, synchronous visuo-tactile stimulation and visuo-motor coupling via first-person control are widely used to induce embodiment. However, when these two streams promote different candidate self-locations, their relative contributions to the perceived self-location remain unclear. In this study, we examined perceived self-location using a robot-mediated self-touch paradigm that creates a cue conflict: synchronous visuo-tactile stimulation in this paradigm tends to bias self-location toward the participant’s physical body, whereas visuo-motor coupling via first-person control tends to bias self-location toward a remote robot viewpoint. We compared this conflict condition with control conditions in which either the visuo-tactile or visuo-motor stimulation was attenuated. Perceived self-location was assessed using questionnaire ratings and a behavioral estimate, namely, the Self-Location EstimatEd Pointing (SLEEP), which estimates participants’ perceived self-location using a finger-pointing task in a 360 degree image. Overall, the results are consistent with a stronger contribution of synchronous visuo-tactile stimulation than visuo-motor coupling to perceived self-location in this whole-body embodiment setting.