Virtual Co-Embodiment: Evaluation of the Sense of Agency While Sharing the Control of a Virtual Body Among Two Individuals

Abstract

In this paper, we introduce a concept called "virtual co-embodiment", which enables a user to share their virtual avatar with another entity (e.g., another user, robot, or autonomous agent). We describe a proof-of-concept in which two users can be immersed from a first-person perspective in a virtual environment and can have complementary levels of control (total, partial, or none) over a shared avatar. In addition, we conducted an experiment to investigate the influence of users' level of control over the shared avatar and prior knowledge of their actions on the users' sense of agency and motor actions. The results showed that participants are good at estimating their real level of control but significantly overestimate their sense of agency when they can anticipate the motion of the avatar. Moreover, participants performed similar body motions regardless of their real control over the avatar. The results also revealed that the internal dimension of the locus of control, which is a personality trait, is negatively correlated with the user's perceived level of control. The combined results unfold a new range of applications in the fields of virtual-reality-based training and collaborative teleoperation, where users would be able to share their virtual body.

Individuals Prioritize the Reach Straightness and Hand Jerk of a Shared Avatar over Their Own

“…Twenty volunteers participated in the experiment (all male, mean 21.35 years old ± 1.5 standard deviation (SD)). The sample size was based on previous embodiment (Fribourg et al, 2020) and motor control (Ganesh, et al, 2014) studies involving interaction between human dyads. This number corresponds to an effect size of 0.7, alpha = 0.05, power = 0.8 using the G*Power 3.1 (Faul, Erdfelder, Lang, & Buchner, 2007;Faul, Erdfelder, Buchner, & Lang, 2009).…”

“…Sharing thus enables multiple individuals to collaborate and contribute in the task performed by an avatar potentially decreasing the workload for each user and improving task performance. Sharing of body parts has been shown to lead to changes in the perceived ownership and agency (Fribourg et al, 2020;Hagiwara et al, 2019). On the other hand, it still remains unclear whether and how shared embodiment affects an individual's motor behavior.…”

Knowing the intention behind limb movements of a partner increases embodiment towards the limb of joint avatar

“…In this study, we explore a new concept called “virtual co-embodiment” where two or more users embody one avatar to collaboratively perform joint tasks. Co-embodiment can be achieved in several ways such as reflecting average movements (or movements in different ratios of control) of multiple users to one avatar/robot 7 , 8 , allowing multiple users to control different sections of one avatar limb/robotic arm 9 , and allowing each user to fully control separate limbs of one avatar 10 , 11 . We are focusing on this third method; We utilized an avatar of which left and right limbs could be controlled by two different individuals at the same time while both of them were immersed in the first-person view of the virtual avatar.…”

“…1 A) in VR and showed that the movements of the shared avatar were straighter, and less jerky compared to the movements of the individual participants and the solo body avatar. Fribourg et al 7 introduced the concept of “virtual co-embodiment” and showed that the participants were good at estimating their real levels of control but significantly overestimated their “sense of agency” when they could anticipate the motion of the avatar. These previous studies on virtual co-embodiment have studied avatars of which the movements were determined by averaging the movements of the two participants in real time (occasionally in different ratios of control).…”

“…These previous studies on virtual co-embodiment have studied avatars of which the movements were determined by averaging the movements of the two participants in real time (occasionally in different ratios of control).

Figure 1 Two types of co-embodiment avatar: ( A ) A shared body avatar is controlled by two individuals, and their movements are averaged and reflected in the shared avatar 7 , 8 . ( B ) A joint body avatar is an avatar in which different body parts such as left and right half bodies are controlled by two different individuals.

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