Effect of connection induced upper body movements on embodiment towards a limb controlled by another during virtual co-embodiment

Abstract

Even if we cannot control them, or when we receive no tactile or proprioceptive feedback from them, limbs attached to our bodies can still provide indirect proprioceptive and haptic stimulations to the body parts they are attached to simply due to the physical connections. In this study we investigated whether such indirect movement and haptic feedbacks from a limb contribute to a feeling of embodiment towards it. To investigate this issue, we developed a ’Joint Avatar’ setup in which two individuals were given full control over the limbs in different sides (left and right) of an avatar during a reaching task. The backs of the two individuals were connected with a pair of solid braces through which they could exchange forces and match the upper body postures with one another. Coupled with the first-person view, this simulated an experience of the upper body being synchronously dragged by the partner-controlled virtual arm when it moved. We observed that this passive synchronized upper-body movement significantly reduced the feeling of the partner-controlled limb being owned or controlled by another. In summary, our results suggest that even in total absence of control, connection induced upper body movements synchronized with the visible limb movements can positively affect the sense of embodiment towards partner-controlled or autonomous limbs.

Temporal visuomotor synchrony induces embodiment towards an avatar with biomechanically impossible arm movements

“…While changes in skin conductance may be a good measure of body ownership towards objects like separate rubber hands ( Armel & Ramachandran, 2003 ; Tsuji et al, 2013 ), and partner-controlled limbs ( Hapuarachchi & Kitazaki, 2022 ; Wegner et al, 2004 ), it may not be very reliable for measuring full body illusions according to our results due to lack of evidence supporting the subjective ratings for body ownership. Therefore, other measurements such as proprioceptive drifts ( Botvinick & Cohen, 1998 ; Costantini & Haggard, 2007 ; Tsakiris & Haggard, 2005 ; Tosi et al, 2023 ) and changes in body schema and representation ( Bertoni et al, 2023 ; Hapuarachchi et al, 2023 ; Matamala-Gomez et al, 2020 ) following previous work may better suit as alternative objective measurements for body ownership in future experiments.…”

Shared Avatar for Hand Movement Imitation: Subjective and Behavioral Analyses

“…Such virtual embodiments are based on the concept that one person has one body. However, virtual co-embodiment [20] [21] [22] and virtual multibody embodiment [23][24] [25] have further expanded the perspective of human embodiment as augmented humans [26] [27].…”