Do indicated body part and self locations differ depending on the viewpoint from a self-avatar?

What is it about?

Using a virtual reality (VR) headset, participants experienced a self-avatar from different viewpoints, i.e. it was seen from either eye-height or from chest-height. Before and after experiencing their avatar, the participants were asked to point with a virtual pointer at several of their physical body parts, as well as at the location of the self within their physical body. The participants pointed relatively accurately to some of their body parts (shoulders, chin, and eyes), but very inaccurately to others, particularly the hips, knees, and feet (too low), and the top of the head (too high). Self-localization was indicated across the whole body, as well as above the head, but mostly in the upper face and the upper torso. We only found an influence of viewpoint (eye-height vs chest-height) during the self avatar phase for the body part localizations, not for self-localization. After the avatar seen from chest-height, the participants on average overshot their body parts much more than before the avatar phase. However, after the avatar seen from eye-height, on average no significant change in the indicated body part locations occurred. Interestingly, the self-avatar phase also did not change the indicated self-locations within the body, not even with an unnatural viewpoint, i.e. chest-height. Additionally, on a questionnaire, no significant difference in embodiment between the viewpoint conditions was found.

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Why is it important?

Possibly, body-based cues, or memory, ground the experienced self-location within the body when in VR. However, the present results caution the use of altered viewpoints in applications where veridical position sense of body parts is required.

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