Virtual Hand Illusion Induced by Visuomotor Correlations

Background: Our body schema gives the subjective impression of being highly stable. However, a number of easily-evoked illusions illustrate its remarkable malleability. In the rubber-hand illusion, illusory ownership of a rubber-hand is evoked by synchronous visual and tactile stimulation on a visible rubber arm and on the hidden real arm. Ownership is concurrent with a proprioceptive illusion of displacement of the arm position towards the fake arm. We have previously shown that this illusion of ownership plus the proprioceptive displacement also occurs towards a virtual 3D projection of an arm when the appropriate synchronous visuotactile stimulation is provided. Our objective here was to explore whether these illusions (ownership and proprioceptive displacement) can be induced by only synchronous visuomotor stimulation, in the absence of tactile stimulation.Methodology/Principal Findings: To achieve this we used a data-glove that uses sensors transmitting the positions of fingers to a virtually projected hand in the synchronous but not in the asynchronous condition. The illusion of ownership was measured by means of questionnaires. Questions related to ownership gave significantly larger values for the synchronous than for the asynchronous condition. Proprioceptive displacement provided an objective measure of the illusion and had a median value of 3.5 cm difference between the synchronous and asynchronous conditions. In addition, the correlation between the feeling of ownership of the virtual arm and the size of the drift was significant.Conclusions/Significance: We conclude that synchrony between visual and proprioceptive information along with motor activity is able to induce an illusion of ownership over a virtual arm. This has implications regarding the brain mechanisms underlying body ownership as well as the use of virtual bodies in therapies and rehabilitation

Proxemics with multiple dynamic characters in an immersive virtual environment

An experiment was carried out to examine the impact on electrodermal activity of people when approached by groups of one or four virtual characters at varying distances. It was premised on the basis of proxemics theory that the closer the approach of the virtual characters to the participant, the greater the level of physiological arousal. Physiological arousal was measured by the number of skin conductance responses within a short time period after the approach, and the maximum change in skin conductance level 5 s after the approach. The virtual characters were each either female or a cylinder of human size, and one or four characters approached each subject a total of 12 times. Twelve male subjects were recruited for the experiment. The results suggest that the number of skin conductance responses after the approach and the change in skin conductance level increased the closer the virtual characters approached toward the participants. Moreover, these response variables were inversely correlated with the number of visits, showing a typical adaptation effect. There was some evidence to suggest that the number of characters who simultaneously approached (one or four) was positively associated with the responses. Surprisingly there was no evidence of a difference in response between the humanoid characters and cylinders on the basis of this physiological data. It is suggested that the similarity in this quantitative arousal response to virtual characters and virtual objects might mask a profound difference in qualitative response, an interpretation supported by questionnaire and interview results. Overall the experiment supported the premise that people exhibit heightened physiological arousal the closer they are approached by virtual characters

Eurographics/ ACM SIGGRAPH Symposium on Computer Animation (2010) Posters and Demos Efficient elimination of foot sliding for crowds

Abstract This poster presents an efficient Animation Planning Mediator (APM) designed to animate virtual characters in real time for crowd simulation. The APM selects the most appropriate animation clip available for each character and modifies the skeletal configuration to satisfy constraints given by the virtual environment and crowd simulation (CS) module, such as eliminating foot-sliding. Using a reduced number of animation clips, we blend within and between animation clips to increase the number of possible locomotion types and to adjust the animations to the velocity of each agent as indicated by the CS module. A key advantage of our approach is that it can be easily integrated with any existing real-time crowd simulation module working in continuous space

Agency and responsibility over virtual movements controlled through different paradigms of brain−computer interface

Agency is the attribution of an action to the self and is a prerequisite for experiencing responsibility over its consequences. Here we investigated agency and responsibility by studying the control of movements of an embodied avatar, via brain computer interface (BCI) technology, in immersive virtual reality. After induction of virtual body ownership by visuomotor correlations, healthy participants performed a motor task with their virtual body. We compared the passive observation of the subject's ‘own’ virtual arm performing the task with (1) the control of the movement through activation of sensorimotor areas (motor imagery) and (2) the control of the movement through activation of visual areas (steady‐state visually evoked potentials). The latter two conditions were carried out using a brain–computer interface (BCI) and both shared the intention and the resulting action. We found that BCI‐control of movements engenders the sense of agency, which is strongest for sensorimotor areas activation. Furthermore, increased activity of sensorimotor areas, as measured using EEG, correlates with levels of agency and responsibility. We discuss the implications of these results for the neural basis of agency

Full Body Acting Rehearsal in a Networked Virtual Environment-A Case Study

In order to rehearse for a play or a scene from a movie, it is generally required that the actors are physically present at the same time in the same place. In this paper we present an example and experience of a full body motion shared virtual environment (SVE) for rehearsal. The system allows actors and directors to meet in an SVE in order to rehearse scenes for a play or a movie, that is, to perform some dialogue and blocking (positions, movements, and displacements of actors in the scene) rehearsal through a full body interactive virtual reality (VR) system. The system combines immersive VR rendering techniques as well as network capabilities together with full body tracking. Two actors and a director rehearsed from separate locations. One actor and the director were in London (located in separate rooms) while the second actor was in Barcelona. The Barcelona actor used a wide field-of-view head-tracked head-mounted display, and wore a body suit for real-time motion capture and display. The London actor was in a Cave system, with head and partial body tracking. Each actor was presented to the other as an avatar in the shared virtual environment, and the director could see the whole scenario on a desktop display, and intervene by voice commands. A video stream in a window displayed in the virtual environment also represented the director. The London participant was a professional actor, who afterward commented on the utility of the system for acting rehearsal. It was concluded that full body tracking and corresponding real-time display of all the actors' movements would be a critical requirement, and that blocking was possible down to the level of detail of gestures. Details of the implementation, actors, and director experiences are provided

Conversations between self and self as Sigmund Freud—A virtual body ownership paradigm for self counselling

When people see a life-sized virtual body (VB) from first person perspective in virtual reality they are likely to have the perceptual illusion that it is their body. Additionally such virtual embodiment can lead to changes in perception, implicit attitudes and behaviour based on attributes of the VB. To date the changes that have been studied are as a result of being embodied in a body representative of particular social groups (e.g., children and other race). In our experiment participants alternately switched between a VB closely resembling themselves where they described a personal problem, and a VB representing Dr Sigmund Freud, from which they offered themselves counselling. Here we show that when the counsellor resembles Freud participants improve their mood, compared to the counsellor being a self-representation. The improvement was greater when the Freud VB moved synchronously with the participant, compared to asynchronously. Synchronous VB movement was associated with a much stronger illusion of ownership over the Freud body. This suggests that this form of embodied perspective taking can lead to sufficient detachment from habitual ways of thinking about personal problems, so as to improve the outcome, and demonstrates the power of virtual body ownership to effect cognitive changes

Automated psychological therapy using immersive virtual reality for treatment of fear of heights: A single-blind, parallel-group, randomised controlled trial

Background Engaging, interactive, and automated virtual reality (VR) treatments might help solve the unmet needs of individuals with mental health disorders. We tested the efficacy of an automated cognitive intervention for fear of heights guided by an avatar virtual coach (animated using motion and voice capture of an actor) in VR and delivered with the latest consumer equipment. Methods We did a randomised trial of automated VR versus usual care. We recruited adults aged older than 18 years with a fear of heights by radio advertisements in Oxfordshire, UK. We diagnosed fear of heights if participants scored more than 29 on the Heights Interpretation Questionnaire (HIQ). We randomly allocated participants by computer in a 1:1 ratio to either automated VR delivered in roughly six 30-min sessions administered about two to three times a week over a 2-week period (intervention group) or to usual care (control group). Randomisation was stratified by severity of fear of heights. The research team, who were unaware of the random allocation, administered three fear-of-height assessments, at baseline (0 weeks), at the end of treatment (2 weeks), and at follow-up (4 weeks). The primary outcome measure was HIQ score (range 16–80, with higher scores indicating greater severity). This trial is registered with the ISRCTN registry, number ISRCTN11898283. Findings Between Nov 25, 2017, and Feb 27, 2018, 100 individuals were enrolled and underwent randomisation, of whom 49 were assigned to the VR treatment group and 51 to the control group. All participants completed the 4-week follow-up. The mean total treatment time in VR was 124·43 min (SD 34·23). Compared with participants in the control group, the VR treatment reduced fear of heights at the end of treatment (mean change score −24·5 [SD 13·1] in the VR group vs −1·2 [7·3] in the control group; adjusted difference −24·0, 95% CI −27·7 to −20·3; Cohen's d=2·0; p<0·0001). The benefit was maintained at follow-up (mean change score −25·1 [SD 13·9] in the VR group vs −1·5 [7·8] in the control group; adjusted difference −24·3, 95% CI −27·9 to −20·6; Cohen's d=2·0; p<0·0001). The number needed to treat to at least halve the fear of heights was 1·3. No adverse events were reported. Interpretation Psychological therapy delivered automatically by a VR coach can produce large clinical benefits. Evidence-based VR treatments have the potential to greatly increase treatment provision for mental health disorders

Comparing and Evaluating Real Time Character Engines for Virtual Environments

As animated characters increasingly become vital parts of virtual environments, then the engines that drive these characters increasingly become vital parts of virtual environment software. This paper gives an overview of the state of the art in character engines, and proposes a taxonomy of the features that are commonly found in them. This taxonomy can be used as a tool for comparison and evaluation of different engines. In order to demonstrate this we use it to compare three engines. The first is Cal3D, the most commonly used open source engine. We also introduce two engines created by the authors, Piavca and HALCA. The paper ends with a brief discussion of some other popular engines

Automated psychological therapy using immersive virtual reality for treatment of fear of heights:a single-blind, parallel-group, randomised controlled trial

Background: Engaging, interactive, and automated virtual reality (VR) treatments might help solve the unmet needs of individuals with mental health disorders. We tested the efficacy of an automated cognitive intervention for fear of heights guided by an avatar virtual coach (animated using motion and voice capture of an actor) in VR and delivered with the latest consumer equipment. Methods: We did a randomised trial of automated VR versus usual care. We recruited adults aged older than 18 years with a fear of heights by radio advertisements in Oxfordshire, UK. We diagnosed fear of heights if participants scored more than 29 on the Heights Interpretation Questionnaire (HIQ). We randomly allocated participants by computer in a 1:1 ratio to either automated VR delivered in roughly six 30-min sessions administered about two to three times a week over a 2-week period (intervention group) or to usual care (control group). Randomisation was stratified by severity of fear of heights. The research team, who were unaware of the random allocation, administered three fear-of-height assessments, at baseline (0 weeks), at the end of treatment (2 weeks), and at follow-up (4 weeks). The primary outcome measure was HIQ score (range 16–80, with higher scores indicating greater severity). This trial is registered with the ISRCTN registry, number ISRCTN11898283. Findings: Between Nov 25, 2017, and Feb 27, 2018, 100 individuals were enrolled and underwent randomisation, of whom 49 were assigned to the VR treatment group and 51 to the control group. All participants completed the 4-week follow-up. The mean total treatment time in VR was 124·43 min (SD 34·23). Compared with participants in the control group, the VR treatment reduced fear of heights at the end of treatment (mean change score −24·5 [SD 13·1] in the VR group vs −1·2 [7·3] in the control group; adjusted difference −24·0, 95% CI −27·7 to −20·3; Cohen's d=2·0; p&lt;0·0001). The benefit was maintained at follow-up (mean change score −25·1 [SD 13·9] in the VR group vs −1·5 [7·8] in the control group; adjusted difference −24·3, 95% CI −27·9 to −20·6; Cohen's d=2·0; p&lt;0·0001). The number needed to treat to at least halve the fear of heights was 1·3. No adverse events were reported. Interpretation: Psychological therapy delivered automatically by a VR coach can produce large clinical benefits. Evidence-based VR treatments have the potential to greatly increase treatment provision for mental health disorders.</p