The Influence of the Viewpoint in a Self-Avatar on Body Part and Self-Localization.

The goal of this study is to determine how a self-avatar in virtual reality, experienced from different viewpoints on the body (at eye- or chest-height), might influence body part localization, as well as self-localization within the body. Previous literature shows that people do not locate themselves in only one location, but rather primarily in the face and the upper torso. Therefore, we aimed to determine if manipulating the viewpoint to either the height of the eyes or to the height of the chest would influence self-location estimates towards these commonly identified locations of self. In a virtual reality (VR) headset, participants were asked to point at several of their body parts (body part localization) as well as ”directly at you” (self-localization) with a virtual pointer. Both pointing tasks were performed before and after a self-avatar adaptation phase where participants explored a co-located, scaled, gender-matched, and animated self-avatar. We hypothesized that experiencing a self-avatar might reduce inaccuracies in body part localization, and that viewpoint would influence pointing responses for both body part and self-localization. Participants overall pointed relatively accurately to some of their body parts (shoulders, chin, and eyes), but very inaccurately to others, with large undershooting for the hips, knees, and feet, and large overshooting for the top of the head. Self-localization was spread across the body (as well as above the head) with the following distribution: the upper face (25%), the upper torso (25%), above the head (15%) and below the torso (12%). We only found an influence of viewpoint (eye- vs chest-height) during the self-avatar adaptation phase for body part localization and not for self-localization. The overall change in error distance for body part localization for the viewpoint at eye-height was small (M = –2.8 cm), while the overall change in error distance for the viewpoint at chest-height was significantly larger, and in the upwards direction relative to the body parts (M = 21.1 cm). In a post-questionnaire, there was no significant difference in embodiment scores between the viewpoint conditions. Most interestingly, having a self-avatar did not change the results on the self-localization pointing task, even with a novel viewpoint (chest-height). Possibly, body-based cues, or memory, ground the self when in VR. However, the present results caution the use of altered viewpoints in applications where veridical position sense of body parts is required.