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Abstract:
In the framework of the experimental induction of full-body illusions the features of the experience of being a distinct entity (selfhood) are altered such that participants identify with and mis-localize themselves towards a virtual body. On the other hand, it has been found that the experience of circular self-motion, or vection, can be induced by rotating a naturalistic visual environment around human participants. Circular vection is likely influenced by a person’s self-localization, since it is the illusion of self-rotation around a specific location. Thus, estimates of vection may serve as indicators for altered self-localization. In the framework of a within-subjects design experiment, male participants viewed an avatar from behind within a naturalistic virtual city in a head-mounted display setup. First, we stroked their back for three minutes while they watched the avatar getting synchronously and congruently stroked, or no visuo-tactile stroking was applied (stimulation factor). Subsequently, we assessed their identification with the avatar with a questionnaire, and then repeated the initial treatment. Finally, we rotated the participants’ perspective around their vertical axis for one minute. During rotation the avatar was in the same location in front of the viewer, rotating around his axis, or in a standing posture (avatar-motion factor). Participants were asked to indicate when they started to experience vection. They reported significantly higher identification with the avatar and self-localization in the avatar’s position after visuo-tactile stimulation. Moreover, when they experienced visuo-tactile stimulation, regardless of the avatar-motion factor, participants showed a later onset of vection. One possible explanation for these results is that participants perceived themselves as partially localized in the avatar’s position, and in turn this decrease in their accuracy of self-localization delayed their experience of circular vection. Consequently, we suggest estimates of self-motion as a new measure for selfhood and embodiment, and specifically for self-localization.
