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

doi:10.21203/rs.3.rs-1545935/v1

Download PDF

Article

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

https://doi.org/10.21203/rs.3.rs-1545935/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

We investigated whether sharing a common goal with a partner and knowing the partner’s intention behind arm movements affect the senses of agency and ownership towards an arm fully controlled by the partner. Participant dyads controlled different limbs (left and right arms) of the same virtual avatar immersed in a virtual environment in first person perspective to collaboratively perform a reaching task that involved joint action as well as separate reaching tasks with the partner’s target visible or invisible to each other. The results showed that the senses of agency and ownership towards the arm controlled by the partner were significantly higher when the participant dyads shared a common intention or when they were allowed to see their partner’s target, compared to when the partner’s target was invisible. The skin conductance was significantly lower towards the arm controlled by the partner compared to the arm fully controlled by the participants in all goal conditions. These results provide insights regarding how sensory information necessary for predicting the partner’s intentions relate to embodiment of the partner’s limbs during virtual co-embodiment.

embodiment

sense of body ownership

sense of agency

joint avatar

joint action

In recent years, topics such as ‘’Metaverse’’ have gained enormous attention with the advancement of related technologies. Metaverse is a multiuser environment merging physical reality with digital virtuality and is based on the convergence of technologies such as virtual reality (VR) and augmented reality (AR) that enable multisensory interactions with virtual environments, digital objects and people (Mystakidis, 2022). As a result of various restrictions due to COVID-19 in recent years, it is highly likely that working, skill-learning, exercising and socializing would shift more towards VR and cyberspace in the future. The metaverse is expected to be a realistic society, while the concepts of race, gender, and even physical disability would be weakened (Duan et al., 2021). Virtual embodiment enables us to have an illusory body ownership towards bodies in different skin color (Peck et al., 2013), gender (Lopez et al., 2019), and size (Tambone et al., 2021), bodies that are invisible or transparent (Guterstam et al., 2013;2015, Martini et al., 2015, Kondo et al., 2018;2020), and non-human agents (Hoffmann et al., 2018) and animals (Krekhov et al., 2019). Here, we are interested in the idea of minimizing physical disabilities of users in the virtual worlds through specially designed virtual avatars (Inami et al., 2022). Human movement augmentation such as supernumerary limbs, body-parts remapping, and exoskeletons expands physical abilities both for impaired and unimpaired individuals (Eden, et al., 2022; Sasaki et al., 2017; Umezawa, et al., 2021; Kondo, et al., 2020). In social VR platforms, with appropriate software developments and accurate body movement tracking, it would be possible for multiple users to embody one avatar and engage in various tasks together. This may allow disabled VR users to get support from others and increase work efficiency as well as user satisfaction. The present study takes this social approach.

Although the concept of two individuals co-embodying one avatar in first-person view is rather new, it has been proposed in a few recent studies (Fig. 1A). Hagiwara et al., 2020 conducted an experiment where two human participants were embodied within a concurrent shared avatar 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., 2020 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). Although averaging movements may have its benefits for some tasks for normal VR users, allowing a partner to completely control the virtual avatar’s limb corresponding to a person’s missing/immovable limb would be more applicable in the case of disabled VR users such as hemiplegic patients and amputees. Such aid by partners would allow amputees to weaken disabilities and perform complicated tasks in one avatar where each participant can focus on one detailed sub task. We have developed this type of co-embodiment avatar as a joint body avatar, in which the left half of the avatar is controlled by a user and the right half of the avatar is controlled by another (Fig. 1B, Video S1). However, allowing another person to fully control a limb of a virtual avatar in which an individual is immersed in first person perspective may cause a severe lack of “sense of embodiment” towards that limb, which may lead to an uncomfortable experience associated with the feeling of being partly possessed by someone else. Therefore, addressing this lack of sense of embodiment towards limbs controlled by others is necessary for a pleasant virtual co-embodiment.

According to Kilteni et al., 2012, “sense of embodiment” consists of three subcomponents called (1) sense of self-location: the ability to perceive the location of one’s body parts (Lenggenhager et al., 2009, Blanke, & Metzinger, 2009), (2) sense of agency: the sense of having control of motion (Haggard, 2005, Blanke, & Metzinger, 2009), and (3) sense of body ownership: one’s self-attribution of the body (Gallagher, 2000). Multiple studies using VR (Gonzalez-Franco et al., 2010, Aymerich-Franch, & Ganesh, 2016) as well as physical objects such as rubber hands (Botvinick, & Cohen, 1998, Kalckert, & Ehrsson, 2014) have investigated on these subcomponents and shown that humans can elicit embodiment towards virtual and physical objects other than their own bodies. While studies on inducing ownership towards external objects like rubber hand illusion (Botvinick, & Cohen, 1998) have claimed that visuo-tactile synchrony or synchronized active or passive movements are necessary for embodiment of a rubber hand, studies on virtual avatars in VR claim avatar appearance (Paludan, et al., 2016), visuomotor congruence or avatar control (Caspar, et al., 2015), and user point of view (Gorisse, et al., 2017) to be factors affecting embodiment. Since most of these studies on embodiment of virtual avatars have been conducted on a one-to-one basis (one person controlling all limbs of one avatar), there is a lack of knowledge regarding factors affecting embodiment towards body parts controlled by others. In such cases, ‘control’ for the limb which is known to be one of the most crucial factors affecting sense of agency according to Fribourg et al 2020, will be lost consequently reducing or even cancelling embodiment towards the limb. Therefore, it is crucial to explore other possible factors that would affect embodiment towards such uncontrolled limbs. In our previous study, we connected two participants' backs with a hard brace and found that connection force feedback synchronized with the movements of the joint virtual avatar could increase illusory body ownership towards a limb controlled by another. (Harin et al., under review). However, for realizing the joint body in virtual environments, it is not reasonable to connect users physically. Therefore, we need other factors to increase embodiment towards the limb controlled by another person without connection force feedback.

In this study, we investigated whether sense of embodiment towards a limb fully controlled by a partner would change depending on the nature of the task itself performed in the co-embodied avatar. The task of the joint avatar can be considered as 'joint action'. Sebanz et al. (2006) defined joint action as any form of social interaction whereby two or more individuals “coordinate” their actions in space and time to bring about a change in the environment (Sebanz et al., 2006). For example, two people carrying a table together would require both of them to coordinate their actions in a temporally and spatially precise manner to successfully execute the task. Some coordination mechanisms depend on sensorimotor information shared between co-actors, thereby making joint attention, prediction, non-verbal communication, or the sharing of emotional states possible (Vesper et al., 2017). Previous studies related to joint attention have suggested that the ability to direct one’s attention to where an interaction partner is attending provides a basic mechanism for sharing representations of objects and events (Frischen, & Tipper, 2004, Tollefsen, 2005) which may possibly encourage the ‘we’ intention or the ‘we-mode’ (Gallotti, & Frith, 2013) believed by some philosophers to be what joint action mostly depends on (Tollefson, 2005). Here, we thought of the possibility of enhancing embodiment towards a co-embodied avatar by encouraging we-mode through sensory (visual) information manipulation during joint action, to eventually investigate on the relationship between embodiment and joint attention (or the sensory information responsible for joint attention). Therefore, we hypothesized there to be an increase in embodiment if the individual and the partner shared one common intention/goal compared to having their own separate intentions before observing the partner’s action during the task. Furthermore, we hypothesized that in the case of having two different targets, the embodiment would be higher when the partner’s target is visible compared to when it is invisible. To test these hypotheses, we conducted an experiment using a joint avatar. Our joint avatar was an avatar co-embodied by two individuals together of which one participant fully controlled the left-side limbs while another fully controlled the right-side limbs in first person perspective. In our experiment, participant dyads performed three types of reaching tasks involving and not involving joint action (Fig. 2).

We named the three reaching tasks/conditions of our study as “Same goal”, “Different goals: Visible”, and “Different goals: Invisible”. The “Same goal” condition consisted of a reaching task where the two participants in the dyad reached yellow spheres in front of them using the two hands of the joint avatar. In “Different goals: Visible” and “Different goals: Invisible” conditions, the two participants reached two different targets with the left and right arms. The red targets were reached with the left hand of the avatar and the blue targets were reached with the right hand of the avatar. 100 common targets or 100 pairs of targets appeared in each condition, which was blocked as a session.

Sense of body ownership towards the non-controlled arm was higher in Same goal and Different goals: Visible conditions compared to the Different goals: Invisible condition.

Questionnaire at the end of each session consisted of 6 items, 3 regarding the left arm and 3 regarding the right arm of the joint avatar. Participants answered all items (Q1. The movements of the virtual left arm seemed to be my movements, Q2. I felt as if the virtual left arm I saw was my own left arm, Q3. It seemed as if I felt the touch of the target sphere at the end of my left index finger, Q4. The movements of the virtual right arm seemed to be my movements, Q5. I felt as if the virtual right arm I saw was my own right arm, Q6. It seemed as if I felt the touch of the target sphere at the end of my right index finger). Questionnaire answers were accepted in a 7-point Likert scale from − 3 to + 3 where − 3 meant “Strongly disagree” and + 3 meant “Strongly agree”.

Using the answers, senses of ownership and agency towards left and right sides of the joint avatar for each condition were calculated as follows referring the Avatar embodiment standardized questionnaire by Peck, & Gonzalez-Franco (2021).

Sense of body ownership towards the left arm = Q1

Sense of agency towards the left arm = (Q2 + Q3)/2

Sense of body ownership towards the right arm = Q4

Sense of agency towards the right arm = (Q5 + Q6)/2

The results were grouped into “controlled arm” (the arm the participant controlled) and “non-controlled arm” (the arm that was controlled by the partner of the participant). Figures 4 and 5 summarize the results of the questionnaires.

We calculated the sense of body ownership (Fig. 4) towards the two arms of the joint avatar in the three conditions (Same goal, Different goals: Visible, Different goals: Invisible). A two-way repeated measures ANOVA with ART (aligned rank transformation) procedure (Wobbrock et al., 2011) was conducted since some of the data significantly deviated from normality according to the results of Shapiro-Wilk tests (controlled arm for Same goal: W = .958, p = .500, non-controlled arm for Same goal: W = .933, p = .180, controlled arm for Different goals: Visible: W = .874, p = .014, non-controlled arm for Different goals: Visible: W = .914, p = .076, controlled arm for Different goals: Invisible: W = .911, p = .067, non-controlled arm for Different goals: Invisible: W = .844, p = .004). There was a significant interaction between the condition and arm (F(2,38) = 7.622, p = .002, \({\eta }_{p}^{2}\)=.286).

Significant simple main effects on the side condition were obtained in all goal conditions, and the sense of ownership was higher in the controlled arm condition than the non-controlled arm condition (the Same goal: F(1,19) = 78.641, p < .001, \({\eta }_{p}^{2}\)=.805, the Different goals: Visible: F(1,19)=96.404, p<.001, \({\eta }_{p}^{2}\)=.835, the Different goals: Invisible: F(1,19)=113.49, p<.001, \({\eta }_{p}^{2}\)=.857).

Significant simple main effects on the goal condition were seen only in the non-controlled arm (F(2,38) = 9.292, p < .001, \({\eta }_{p}^{2}\)=.328). Tukey post hoc tests confirmed that ownership was significantly higher in the Same goal condition compared to Different goals: Invisible condition (p=.0015, d = 1.201), and significantly higher in the Different goals: Visible condition compared to Different goals: Invisible condition (p = .0021, d = 1.159).

We calculated the sense of agency (Fig. 5) towards the two arms of the joint avatar in the three conditions (Same goal, Different goals: Visible, Different goals: Invisible). A two-way repeated measures ANOVA with ART (aligned rank transformation) procedure (Wobbrock et al., 2011) was conducted since some of the data significantly deviated from normality according to the results of Shapiro-Wilk tests (controlled arm for Same goal: W = .827, p = .002, non-controlled arm for Same goal: W = .935, p = .194, controlled arm for Different goals: Visible: W = .755, p < .001, non-controlled arm for Different goals: Visible: W = .907, p = .055, controlled arm for Different goals: Invisible: W = .815, p = .001, non-controlled arm for Different goals: Invisible: W = .872, p = .013). There was a significant interaction between the condition and arm (F(2,38) = 8.141, p = .001, \({\eta }_{p}^{2}\)=.300).

Significant simple main effects on the side condition were obtained in all goal conditions, and the sense of agency was higher in the controlled arm condition than the non-controlled arm condition (the Same goal: F(1,19) = 94.509, p < .001, \({\eta }_{p}^{2}\)=.833, the Different goals: Visible: F(1,19)=157.38, p<.001, \({\eta }_{p}^{2}\)=.892, the Different goals: Invisible: F(1,19)=174.04, p<.001, \({\eta }_{p}^{2}\)=.902).

Significant simple main effects on the goal condition were seen only in the non-controlled arm (F(2,38) = 0.211, p = .011, \({\eta }_{p}^{2}\)=.211). Tukey post hoc tests confirmed that agency was significantly higher in the Same goal condition compared to Different goals: Invisible condition (p=.0181, d = 0.906), and significantly higher in the Different goals: Visible condition compared to Different goals: Invisible condition (p = .0308, d = 0.837).

Skin conductance response of each participant was calculated every time the threatening stimulus (virtual knife) appeared, as the difference between the maximum value detected in a 10s post-stimulus time window and the baseline calculated as the average value of a 5s pre-stimulus time window at a sample rate of 1000Hz. Figure 6 shows the calculated average skin conductance values when the controlled/non-controlled arm of the joint avatar was stabbed with the virtual knife in the three goal conditions. Two-way repeated measures ANOVA showed no significant interaction between the goal condition and the arm. A significant main effect in the arm showed that the skin conductance response towards the controlled arm was significantly higher than that towards the non-controlled arm (F(1,19) = 6.8201, p = .017, \({\eta }_{p}^{2}\)=.264). However, no main effect of the goal condition or the interaction was observed.

We investigated whether sharing a goal, or being able to see the partner’s goal affects the senses of body ownership and agency towards an arm controlled by the partner when two individuals perform three types of reaching tasks using a joint avatar in VR, of which one individual fully controls the movements of the left arm while the other fully controls the movements of the right arm. Our main interest was on how the visibility and sharing of the partner’s goal affects the embodiment towards the arm controlled by the partner. We found that the sense of ownership and the sense of agency were significantly higher when the goal was common or visible to the partner than when the goal was different and invisible to the partner.

According to Wegner’s theory of apparent mental causation (Wegner, & Wheatley, 1999), “sense of agency” which is a main sub-component of sense of embodiment, arises if (1) an intention precedes an observed action (priority), (2) the intention is compatible with this action (consistency), and (3) the intention is the most likely cause of this action (exclusivity). Although these three conditions apply when the intention and the action belong to the same person, would sense of agency arise if a partner moves an arm of a person’s avatar to match with the intention of the person? Results from our experiment provide an answer to this question. During sharing one goal (same goal condition) as well as knowing the position of the partner’s goal while having two separate goals (different goals: visible condition), the agency towards the arm controlled by the partner (non-controlled arm) was significantly increased compared to the control condition where the partner’s target was invisible while having two separate goals (different goals: invisible condition). This shows that sense of agency does indeed increase when a partner moves an arm of a person’s avatar to match with the intention of the person. Interestingly, in addition to sense of agency, ownership towards the partner’s arm was also significantly increased in a similar manner between the three conditions. Overall, these results suggest that being able to see the partner’s target increases sense of embodiment towards the arm controlled by the partner.

However, among same goal and different goals: visible conditions, there were no significant difference in ownership or agency towards the non-controlled arm. This suggests that being able to know the partner’s objective increases embodiment towards the arm controlled by the partner regardless of the shared or divided nature of the task (equally increased in both cases compared to the control condition).

Furthermore, the senses of agency and ownership were both significantly higher towards the controlled arm than towards the non-controlled arm in all three conditions. Skin conductance results were also significantly higher when the controlled arm was virtually stabbed with a knife compared to when the virtual non-controlled arm was stabbed in all three conditions. However, between the three conditions there was no significant difference among the skin conductance levels towards either of the arms of the joint avatar. In general, these results show that embodiment towards an arm fully controlled by a partner was still significantly lower compared to a fully controlled arm even with goal sharing or knowing the partner’s intentions behind arm movements. Therefore, while we conclude visibility of the partner’s target (which conveys the partner’s intention for arm movements) to be a factor affecting embodiment, we also do point out that visibility alone is not sufficient to induce a level of ownership or agency to an equal level felt towards a fully controlled arm. However, coupled with other factors affecting embodiment towards such limbs, it may be possible to increase embodiment further. Therefore, future studies investigating other factors affecting embodiment towards such limbs such as personality traits/behavior of the partner, different kinds of haptic feedbacks towards the limbs or body, level of trust between the dyads etc. is important. Investigating such factors in isolation as well as coupled together in various combinations may provide further insights regarding embodying limbs controlled by others.

These findings may contribute to inducing illusory senses of ownership and agency towards robotic prosthetics or supernumerary limbs controlled by others or AI to make them feel like parts of the user’s own body. It improves usability and naturalness of such robotic prosthetics or supernumerary limbs.

Limitations of the study

The findings regarding the embodiment towards the non-controlled arm among the three main experiment conditions were not supported by SCR results in this study. Therefore, further investigation of other physiological measures such as proprioceptive drifts and changes in body schema/body image due to experiencing of the joint avatar, may be more appropriate for assessing embodiment in future work.

Participants

Twenty university students as ten dyads (All males, mean age 22.3, SD 2.4) participated in the experiment as dyads. The sample size was determined by a power analysis with an effect size (f) of 0.25 (medium), an alpha of 0.05, and power of 0.80 using G*Power 3.1. All participants were unaware of the hypothesis of the experiments and had normal or corrected-to-normal eyesight. They provided informed consent before the experiment. Additionally, individuals appearing in Video S1 gave their informed consent for publication of identification/images in an online open-access publication. The methods of the experiment were approved by the Ethical Committee for Human-Subject Research at the Toyohashi University of Technology, and all methods were carried out in accordance with the relevant guidelines and regulations.

Setup and Apparatus: The movements of the two participants were measured by a motion capture system (Vicon Bonita10, 12 cameras, 1024 x 1027 pixels, 250 fps). Two computers with the same specifications received the processed information of the motion capture data and presented the virtual environment on head-mounted displays (HMD: HTC VIVE Pro Eye, 1440 x 1600 pixels per eye, 90 x 110deg, 90 Hz refresh) of both participants. The virtual environment and experiment tasks were created using Unity (2017.4.1f1). BIOPAC MP 160 and wireless PPG and EDA amplifiers (BN-PPGED) were used to record the skin conductance response (SCR). A wireless transmitter (BN-PPGED) was placed on each participant’s wrist. Two disposable electrodes (EL507) were pasted to the distal phalanges of their middle and ring fingers. Two lead cables (BN-EDALEAD2) connected the wireless transmitter to the electrodes. The SCR data were recorded at 1000 Hz.

Stimuli and Conditions

The experiment consisted of three conditions. In each session, one participant controlled the left side of the joint avatar while the other controlled the right side throughout the experiment, both in first-person view. We named the three conditions “Same goal”, “Different goals: visible”, and “Different goals: invisible”. In the “same goal condition”, one yellow target appeared in front of the joint avatar and participants were asked to collaborate and touch the target with both hands of the joint avatar. In the different goals: visible condition, two targets (one blue and one red) appeared in front of the avatar and participants were asked to touch the blue target with the right hand and red target with the left hand of the joint avatar. Different goals: invisible condition was the same as different goals: visible condition, but the target of their partner was invisible for each participant. All targets were spheres of 5cm diameter and were erased 200ms after reached appropriately for each condition. After erasing, the next target appeared 2s later. The targets appeared at random positions inside the areas shown in Fig. 7. Each session consisted of 100 reaches per participant and on the final reach of each session, a stimulus of a knife stabbing either the left or the right hand of the joint avatar was displayed.

Procedure

The participants were instructed to reach the targets and keep the hand touching the target until it erases before returning their hands back to the original position. In the last target reach at the end of each session, we displayed a stimulus of a knife stabbing one of the hands of the joint avatar (see Fig. 3). To make the knife visible to both participants, the last target position was pre-chosen to be towards the center of the avatar in a clearly visible position and the final target/two targets was/were not erased on touch hence requiring the participants to keep touching the targets. We measured skin conductance response of participants during the stimulus of the knife to assess embodiment towards each arm of the avatar in each condition.

The experiment consisted of six sessions (3 conditions x 2 repetitions). Each condition was blocked as a session. In the two repetitions for each condition, left hand was stabbed at the end of one repetition while the right hand was stabbed in the other. The order of sessions was randomized for each dyad. One session lasted 5–7 minutes and after each session, both participants answered a questionnaire regarding how they felt about the left and right arms of the joint avatar. The questionnaire was based on a previous study (Peck, & Gonzalez-Franco, 2021). There were size items that were presented in random order:

Q1. The movements of the virtual left arm seemed to be my movements

Q2. I felt as if the virtual left arm I saw was my own left arm

Q3. It seemed as if I felt the touch of the target sphere at the end of my left index finger

Q4. The movements of the virtual right arm seemed to be my movements

Q5. I felt as if the virtual right arm I saw was my own right arm

Q6. It seemed as if I felt the touch of the target sphere at the end of my right index finger

Using the answers, we calculated senses of ownership and agency for the “controlled arm” (the arm of the joint avatar controlled by the participant), and the “noncontrolled arm” (arm of the joint avatar controlled by the partner of the participant). Skin conductance response was calculated as the difference between the maximum value detected in a 10s post-stimulus (knife) time window and the baseline calculated as the average value of a 5s pre-stimulus time window (for both participants in each session).

ACKNOWLEDGEMENTS

This research was supported by JST ERATO Grant Number JPMJER1701 (Inami JIZAI Body Project), and JSPS KAKENHI Grant Number JP20H04489. The preliminary results of this study were presented as a poster at a conference (Harin and Kitazaki, 2022).

AUTHOR CONTRIBUTIONS

Conceptualization, H.H., and M.K.; Methodology, H.H., and M.K.; Investigation, H.H.; Writing – Original Draft, H.H., and M.K.; Writing – Review & Editing, H.H., and M.K.; Funding Acquisition, M.K.; Supervision, M.K.

Data Availability

All data generated or analyzed during this study are available at Mendeley Data.
(http://dx.doi.org/10.17632/fnhvhb5b9z.1).

DECLARATION OF INTERESTS

The authors declare no competing interests.

Mystakidis, S. (2022). Metaverse. Encyclopedia, 2(1), 486–497.
Duan, H., Li, J., Fan, S., Lin, Z., Wu, X., & Cai, W. (2021, October). Metaverse for social good: A university campus prototype. In Proceedings of the 29th ACM International Conference on Multimedia (pp. 153–161).
Peck, T. C., Seinfeld, S., Aglioti, S. M., & Slater, M. (2013). Putting yourself in the skin of a black avatar reduces implicit racial bias. Consciousness and Cognition, 22(3), 779–787.
Lopez, S., Yang, Y., Beltran, K., Kim, S. J., Cruz Hernandez, J., Simran, C., … Yuksel,B. F. (2019, May). Investigating implicit gender bias and embodiment of white males in virtual reality with full body visuomotor synchrony. In Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems (pp. 1–12).
Tambone, R., Poggio, G., Pyasik, M., Burin, D., Dal Monte, O., Schintu, S., … Pia,L. (2021). Changing your body changes your eating attitudes: embodiment of a slim virtual avatar induces avoidance of high-calorie food. Heliyon, 7(7), e07515.
Guterstam, A., Gentile, G., & Ehrsson, H. H. (2013). The invisible hand illusion: multisensory integration leads to the embodiment of a discrete volume of empty space. Journal of Cognitive Neuroscience, 25(7), 1078–1099.
Guterstam, A., Abdulkarim, Z., & Ehrsson, H. H. (2015). Illusory ownership of an invisible body reduces autonomic and subjective social anxiety responses. Scientific Reports, 5: 9831, doi: 10.1038/srep09831
Martini, M., Kilteni, K., Maselli, A., & Sanchez-Vives, M. V. (2015). The body fades away: investigating the effects of transparency of an embodied virtual body on pain threshold and body ownership. Scientific Reports, 5(1), 1–8.
Kondo, R., Sugimoto, M., Minamizawa, K., Hoshi, T., Inami, M., and Kitazaki, M. (2018). Illusory body ownership of an invisible body interpolated between virtual hands and feet via visual-motor synchronicity, Scientific Reports, 8:7541 DOI:10.1038/s41598-018-25951-2
Kondo, R., Tani, Y., Sugimoto, M., Inami, M., and Kitazaki, M. (2020). Scrambled body differentiates body part ownership from the full body illusion. Scientific Reports, 10:5274, DOI: 10.1038/s41598-020-62121-9
Hoffmann, L., Bock, N., & vd Pütten, A. M. R. (2018, March). The peculiarities of robot embodiment (EmCorp-Scale): development, validation and initial test of the embodiment and corporeality of artificial agents scale. In 2018 13th ACM/IEEE International Conference on Human-Robot Interaction (HRI) (pp. 370–378). IEEE.
Krekhov, A., Cmentowski, S., Emmerich, K., & Krüger, J. (2019, October). Beyond human: Animals as an escape from stereotype avatars in virtual reality games. In Proceedings of the Annual Symposium on Computer-Human Interaction in Play (pp. 439–451).
Inami, M., Uriu, D., Kashino, Z., Yoshida, S., Saito, H., Maekawa, A., and Kitazaki, M. (2022). Cyborgs, Human Augmentation, Cybernetics, and JIZAI Body, In Proceedings of Augmented Humans 2022, DOI: 10.1145/3519391.3519401
Eden, J., Bräcklein, M., Ibáñez, J., Barsakcioglu, D. Y., Di Pino, G., Farina, D.,… Mehring, C. (2022). Principles of human movement augmentation and the challenges in making it a reality. Nature Communications, 13(1), 1–13.
Sasaki, T., Saraiji, M. Y., Fernando, C. L., Minamizawa, K. & Inami, M. Metalimbs: multiple arms interaction metamorphism. In ACM SIGGRAPH Emerging Technologies, 1–2 (ACM, Los Angeles, California, USA, 2017).
Umezawa, K., Suzuki, Y., Ganesh, G., & Miyawaki, Y. (2022). Bodily ownership of an independent supernumerary limb: An exploratory study. Scientific Reports, 12:2339, doi: 10.1038/s41598-022-06040-x
Kondo, R., Tani, Y., Sugimoto, M., Minamizawa, K., Inami, M., & Kitazaki, M. (2020). Re-association of body parts: illusory ownership of a virtual arm associated with the contralateral real finger by visuo-motor synchrony. Frontiers in Robotics and AI, 7, 26.
Hagiwara, T., Ganesh, G., Sugimoto, M., Inami, M., & Kitazaki, M. (2020). Individuals prioritize the reach straightness and hand jerk of a shared avatar over their own. iScience, 23(12), 101732.
Fribourg, R., Ogawa, N., Hoyet, L., Argelaguet, F., Narumi, T., Hirose, M., & Lécuyer, A. (2020). Virtual co-embodiment: evaluation of the sense of agency while sharing the control of a virtual body among two individuals. IEEE Transactions on Visualization and Computer Graphics, 27(10), 4023–4038.
Kilteni, K., Groten, R., & Slater, M. (2012). The sense of embodiment in virtual reality. Presence: Teleoperators and Virtual Environments, 21(4), 373–387.
Lenggenhager, B., Mouthon, M., & Blanke, O. (2009). Spatial aspects of bodily self-consciousness. Consciousness and Cognition, 18(1), 110–117.
Blanke, O., & Metzinger, T. (2009). Full-body illusions and minimal phenomenal selfhood. Trends in Cognitive Sciences, 13(1), 7–13.
Haggard, P. (2005). Conscious intention and motor cognition. Trends in Cognitive Sciences, 9(6), 290–295.
Gallagher, S. (2000). Philosophical conceptions of the self: implications for cognitive science. Trends in Cognitive Sciences, 4(1), 14–21.
M. González-Franco, D. Pérez-Marcos, B. Spanlang and M. Slater, "The contribution of real-time mirror reflections of motor actions on virtual body ownership in an immersive virtual environment," 2010 IEEE Virtual Reality Conference (VR), 2010, pp. 111–114.
Aymerich-Franch L, Ganesh G. (2016). The role of functionality in the body model for self-attribution. Neuroscience Research, 104, 31–37. doi: 10.1016/j.neures.2015.11.001.
Botvinick, M., & Cohen, J. (1998). Rubber hands ‘feel’touch that eyes see. Nature, 391(6669), 756–756.
Kalckert, A., & Ehrsson, H. H. (2014). The moving rubber hand illusion revisited: Comparing movements and visuotactile stimulation to induce illusory ownership. Consciousness and Cognition, 26, 117–132.
Paludan, A., Elbaek, J., Mortensen, M., Zobbe, M., Nilsson, N. C., Nordahl, R., …Serafin, S. (2016, March). Disguising rotational gain for redirected walking in virtual reality: Effect of visual density. In 2016 IEEE Virtual Reality (VR) (pp. 259–260). IEEE.
Gorisse, G., Christmann, O., Amato, E. A., & Richir, S. (2017). First-and third-person perspectives in immersive virtual environments: presence and performance analysis of embodied users. Frontiers in Robotics and AI, 4, 33.
Caspar, E. A., Cleeremans, A., & Haggard, P. (2015). The relationship between human agency and embodiment. Consciousness andCcognition, 33, 226–236.
Fribourg, R., Argelaguet, F., Lécuyer, A., & Hoyet, L. (2020). Avatar and sense of embodiment: Studying the relative preference between appearance, control and point of view. IEEE Transactions on Visualization and Computer Graphics, 26(5), 2062–2072.
Hapuarachchi H., Ganesh, G., Hagiwara, T., and Kitazaki, M. (Under review). Connection force feedback in joint avatar increases embodiment towards a body part controlled by another.
Sebanz, N., Bekkering, H., & Knoblich, G. (2006). Joint action: bodies and minds moving together. Trends in cognitive sciences, 10(2), 70–76.
Vesper, C., Abramova, E., Bütepage, J., Ciardo, F., Crossey, B., Effenberg, A., …Wahn, B. (2017). Joint action: mental representations, shared information and general mechanisms for coordinating with others. Frontiers in Psychology, 7, 2039.
Frischen, A., & Tipper, S. P. (2004). Orienting attention via observed gaze shift evokes longer term inhibitory effects: implications for social interactions, attention, and memory. Journal of Experimental Psychology: General, 133(4), 516.
Tollefsen, D. (2005). Let’s pretend! Children and joint action. Philosophy of the Social Sciences, 35(1), 75–97.
Gallotti, M., & Frith, C. D. (2013). Social cognition in the we-mode. Trends in Cognitive Sciences, 17(4), 160–165.
Peck, T. C., & Gonzalez-Franco, M. (2021). Avatar embodiment. a standardized questionnaire. Frontiers in Virtual Reality, 1, 44.
Wobbrock, J. O., Findlater, L., Gergle, D., & Higgins, J. J. (2011, May). The aligned rank transform for nonparametric factorial analyses using only anova procedures. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (pp. 143–146).
Wegner, D. M., & Wheatley, T. (1999). Apparent mental causation: Sources of the experience of will. American Psychologist, 54(7), 480.
Harin, H., and Kitazaki, M. (2022). Knowing the partner's objective increases embodiment towards a limb controlled by the partner, IEEE VR 2022 Conference, 12–16 March 2022, Poster. Proceedings of IEEE VR 2022, 802–803. DOI: 10.1109/VRW55335.2022.00252

No competing interests reported.

Download PDF

Editorial decision: Major revision
24 May, 2022
Reviews received at journal
22 May, 2022
Reviewers agreed at journal
12 May, 2022
Reviewers invited by journal
12 May, 2022
Editor assigned by journal
12 May, 2022
Editor invited by journal
27 Apr, 2022
Submission checks completed at journal
27 Apr, 2022
First submitted to journal
11 Apr, 2022

You are reading this latest preprint version

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

Status:

Version 1

Abstract

Figures

Introduction

Results

Discussion

Limitations of the study

Methods

Stimuli and Conditions

Procedure

Declarations

References

Additional Declarations

Supplementary Files

Status:

Version 1