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

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

Empathic embarrassment towards non-human agents in virtual environments

Abstract Humans feel empathic embarrassment by witnessing others go through embarrassing situations. We examined whether we feel such empathic embarrassment even with robot avatars. Participants observed a human avatar and a robot avatar face a series of embarrassing and non-embarrassing scenarios. We collected data for their empathic embarrassment and the cognitive empathy on a 7-point Likert scale. Both empathic embarrassment and cognitive empathy were significantly higher in the embarrassed condition compared to the non-embarrassed condition with both avatars, and the cognitive empathy was significantly higher with the human avatar. There was a tendency of participants showing a higher level of skin conductance while watching the human avatar go through embarrassing situations compared to the robot avatar. A following experiment showed that the average plausibility of the embarrassed condition was significantly higher with the human avatar compared to the robot avatar. However, plausibility scores for emotion were not significantly different among the conditions. These results suggest that humans can feel empathic embarrassment as well as cognitive empathy for robot avatars while cognitive empathy for robot avatars is comparatively lower, and that part of the empathic difference between human and robot avatars might be due to the difference of their plausibility

Shared Avatar for Hand Movement Imitation: Subjective and Behavioral Analyses

Virtual co-embodiment enables sharing avatars with others in virtual environments and can be applied for training motor skills by allowing teachers to share movements with learners in first-person perspective. We conducted a task where participants were asked to imitate pre-recorded hand movements of a teacher as accurately as possible. The participant’s virtual hand movements were averaged in real-time with those of the teacher (shared avatar hand). We compared their usability ratings and behavior against a controlled condition with full control of the hand (solo avatar hand). The teacher’s hand was displayed facing the same or the opposite direction as the participant’s hand. We hypothesized that using the shared avatar hand would improve imitation over using the solo hand, and the teacher’s hand presented in the same direction is better than that in the opposite direction. Subjective ratings showed that the shared hand was easier to use than the solo hand, and the teacher’s hand when presented in the same direction was easier to imitate than when presented in the opposite direction. Spatial error was less with the opposite-direction presentation than the same-direction presentation of the teacher’s hand, irrespective of movement sharing. Time delay was less when the participants used the shared hand compared to when they used the solo hand, irrespective of the teacher’s hand direction. These results suggest that sharing movements enhances usability and matching speed during movement imitation, and the same-direction presentation of the teacher’s hand improves usability while the opposite-direction presentation improves spatial accuracy of motor imitation