Asura hands: Own and control two left hands in immersive virtual reality environment

Body ownership, which is the feeling that one's body part belongs to oneself, and agency, which is the sense of being able to control one's own body part, can be felt towards fake body parts and those depicted by computer graphics. As part of an attempt to transfer self-body awareness to fake body segments, we investigated whether body ownership and agency are felt towards two visible left hands in an immersive virtual reality environment. One of the two hands shown through virtual reality goggles spatially matched the unseen actual hand. The other hand was fake and displayed at either the 10-cm lateral or medial side of the position of the actual hand. These two left hands moved synchronously with the actual left hand. Participants completed a behavioral test and questionnaire after adapting to the two left hands. In the behavioral test, participants accessed randomly emerging spheres using the seen hands as fast as possible. They used the fake hand to touch a sphere when it appeared near the fake hand 41% of the time when the fake hand was displayed at the medial position of the actual hand. The results of the questionnaire suggest that agency was experienced for the two visible left hands for this condition. By contrast, body ownership was felt mostly against the displayed hand that was spatially consistent with the actual hand. These findings indicate that although agency can be simultaneously felt for two seen left hands, body ownership is felt only for either of the two visible left hands.