Assessing the Clinical Efficacy of a Virtual Reality Tool for the Treatment of Obesity: Randomized Controlled Trial.

BACKGROUND: Virtual reality (VR) interventions, based on cognitive behavioral therapy principles, have been proven effective as complementary tools in managing obesity and have been associated with promoting healthy behaviors and addressing body image concerns. However, they have not fully addressed certain underlying causes of obesity, such as a lack of motivation to change, low self-efficacy, and the impact of weight stigma interiorization, which often impede treatment adherence and long-term lifestyle habit changes. To tackle these concerns, this study introduces the VR self-counseling paradigm, which incorporates embodiment and body-swapping techniques, along with motivational strategies, to help people living with obesity effectively address some of the root causes of their condition. OBJECTIVE: This study aims to assess the clinical efficacy of ConVRself (Virtual Reality self-talk), a VR platform that allows participants to engage in motivational self-conversations. METHODS: A randomized controlled trial was conducted with 68 participants from the bariatric surgery waiting list from the obesity unit of the Vall d'Hebron University Hospital in Barcelona, Spain. Participants were assigned to 1 of 3 groups: a control group (CG), which only received treatment as usual from the obesity unit; experimental group 1 (EG1), which, after intensive motivational interviewing training, engaged in 4 sessions of VR-based self-conversations with ConVRself, and underwent embodiment and body-swapping techniques; and experimental group 2 (EG2), which engaged in 4 VR-based sessions led by a virtual counselor with a prerecorded discourse, and only underwent the embodiment technique. In the case of both EG1 and EG2, the VR interventions were assisted by a clinical researcher. Readiness to change habits, eating habits, and psychological variables, as well as adherence and satisfaction with ConVRself were measured at baseline, after the intervention, 1 week after the intervention, and 4 weeks after the intervention. RESULTS: Regarding the primary outcomes, EG1 (24/68, 35%) and EG2 (22/68, 32%) showed significant improvements in confidence to lose weight compared to the CG (22/68, 32%) at all assessment points (ß=-.16; P=.02). Similarly, EG1 demonstrated a significant increase after the intervention in readiness to exercise more compared to the CG (ß=-.17; P=.03). Regarding the secondary outcomes, EG1 participants showed a significant reduction in uncontrolled eating (ß=.71; P=.01) and emotional eating (ß=.29; P=.03) compared to the CG participants, as well as in their anxiety levels compared to EG2 and CG participants (ß=.65; P=.01). In addition, participants from the experimental groups reported high adherence and satisfaction with the VR platform (EG1: mean 59.82, SD 4.00; EG2: mean 58.43, SD 5.22; d=0.30, 95% CI -0.30 to 0.89). CONCLUSIONS: This study revealed that using VR self-conversations, based on motivational interviewing principles, may have benefits in helping people with obesity to enhance their readiness to change habits and self-efficacy, as well as reduce dysfunctional eating behaviors and anxiety. TRIAL REGISTRATION: ClinicalTrials.gov NCT05094557; https://www.clinicaltrials.gov/study/NCT05094557.

Virtual self-conversation using motivational interviewing techniques to promote healthy eating and physical activity: A usability study.

Introduction: We aim to examine the usability of a Virtual Reality (VR) platform, called ConVRSelf, which has been designed to address the needs of People Living With Obesity (PLWO). Methods: Fourteen participants with a desire to eat healthier and exercise more (6 normal weight and 8 PLWO; Mean age = 41.86, SD = 13.89) were assigned to the experimental group (EG) or the control group (CG). EG participants, after being trained on motivational interviewing skills, engaged in a virtual self-conversation using embodiment and body swapping techniques, which aimed to normalize and resolve their ambivalence to change lifestyle habits. CG participants, embodied in their virtual bodies, participated in a pre-established discourse with a virtual counselor giving them psychoeducational advice about how to change lifestyle habits. A mixed-methods design was used, involving a semi-structured interview and self-report questionnaires, including readiness to change habits (Readiness Rulers), body ownership (Body Ownership Questionnaire, BOQ), and system usability (System Evaluation Questionnaire, SEQ). Thematic content analysis was carried out for qualitative data while statistical data analysis was carried out using SPSS 20.0. Results: Participants from both groups showed high readiness to change lifestyle (Readiness Rulers) before engaging with the virtual experiences, which was maintained at the same level after the interventions and their scores on the SEQ and BOQ were satisfactory. Regarding qualitative information obtained from the interviews, almost all participants found the VR experience to be novel, interesting, and enjoyable. A higher acceptability was observed among PLWO from the EG than normal weight participants from the same group, a promising finding for the ConVRSelf platform, which had been specifically designed to address the needs of PLWO. Conclusion: The ConVRSelf system is well-accepted by participants and is ready to be tested with PLWO in a clinical setting.

Clinical efficacy of a virtual reality tool for the treatment of obesity: study protocol of a randomised controlled trial.

INTRODUCTION: Previous research has shown that it is feasible to integrate motivational interviewing techniques with behavioural and psychological interventions for the treatment of obesity. Moreover, these combined interventions have the potential to improve health-related outcomes of people living with obesity (PLWO) and to afford maintenance of behavioural changes over time. In addition, the use of virtual reality (VR) embodiment techniques in the treatment of eating disorders and obesity has promising preliminary effectiveness. The objective of this study is to assess the clinical efficacy of a VR intervention that uses embodiment and body-swapping techniques and has been specifically developed to cover the needs of PLWO. METHODS AND ANALYSIS: A randomised control trial will be carried out with an estimated sample of 96 participants with body mass index (BMI)>30. The whole duration of the trial will be 12 months. Participants will be recruited from the external consultations of the Vall d'Hebron University Hospital and be randomly assigned to three groups. The experimental group 1 will engage in a virtual self-conversation using the ConVRself platform, the experimental group 2 will participate in a 'pre-established discourse' provided by the virtual counsellor, who will give psychoeducation advice, and the control group will continue with treatment as usual. Readiness to change, BMI, eating habits and physical activity, psychological well-being, body image satisfaction, quality of life in relation to body image, and weight bias internalisation will be assessed at baseline, post intervention, 1-week and 4-week follow-up. Finally, variables related to adherence and satisfaction with the VR tool will be evaluated for the experimental groups. ETHICS AND DISSEMINATION: This study was approved by the Research Projects Committee of the Vall d'Hebron University Hospital. Findings will be disseminated through peer-reviewed journals, reports to the funding body, conferences and other events for the scientific and clinical community, and the general public. TRIAL REGISTRATION NUMBER: NCT05094557.

Neural correlates of disturbance in the sense of agency in schizophrenia: An fMRI study using the 'enfacement' paradigm.

An altered sense of self-awareness and agency has been proposed to underlie symptoms of schizophrenia. In this study, we used the enfacement illusion paradigm - in which perception of another person's face leads to changes in perception of one's own peri-personal space - to examine the brain correlates of the sense of agency and its potential disruption in schizophrenia. Thirty-three schizophrenic patients and 27 healthy controls underwent fMRI scanning during performance of a task designed to elicit the enfacement illusion. Activations were examined using whole-brain analysis and also in an a priori identified region of interest (ROI) in the temporoparietal junction (TPJ), a region that has been described as involved in self/other differentiation and sense of agency. Both groups showed a pattern of cortical activation involving the pre and postcentral cortex, Rolandic operculum, insula, parietal, temporal and occipital cortex bilaterally as well as TPJ (but only right-side in patients). Examination of the TPJ ROI revealed significantly reduced activation on the left in the patients that was associated with poorer insight. The findings suggest brain functional abnormality in schizophrenia related to the formation or maintenance of processes related to self and/or agency. Decreased function in the TPJ may have a role in the impaired insight seen in patients with the disorder.

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

KEY POINTS: Embodiment of a virtual body was induced and its movements were controlled by two different brain-computer interface (BCI) paradigms - one based on signals from sensorimotor versus one from visual cortical areas. BCI-control of movements engenders agency, but not equally for all paradigms. Cortical sensorimotor activation correlates with agency and responsibility. This has significant implications for neurological rehabilitation and neuroethics. ABSTRACT: 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 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 area 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.

An experimental study of a virtual reality counselling paradigm using embodied self-dialogue.

When faced with a personal problem people typically give better advice to others than to themselves. A previous study showed how it is possible to enact internal dialogue in virtual reality (VR) through participants alternately occupying two different virtual bodies - one representing themselves and the other Sigmund Freud. They could maintain a self-conversation by explaining their problem to the virtual Freud and then from the embodied perspective of Freud see and hear the explanation by their virtual doppelganger, and then give some advice. Alternating between the two bodies they could maintain a self-dialogue, as if between two different people. Here we show that the process of alternating between their own and the Freud body is important for successful psychological outcomes. An experiment was carried out with 58 people, 29 in the body swapping Self-Conversation condition and 29 in a condition where they only spoke to a Scripted Freud character. The results showed that the Self-Conversation method results in a greater perception of change and help compared to the Scripted. We compare this method with the distancing paradigm where participants imagine resolving a problem from a first or third person perspective. We consider the method as a possible strategy for self-counselling.

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. FUNDING: Oxford VR, and the National Institute of Health Research Oxford Health Biomedical Research Centre.

Mimicking Schizophrenia: Reducing P300b by Minimally Fragmenting Healthy Participants' Selves Using Immersive Virtual Reality Embodiment.

The most robust and clear biological index differentiating persons with schizophrenia from healthy controls is the drastic reduction of the amplitude of their P300b event-related brain potential (ERP). However, the cause of that reduction remains obscure. Nevertheless, the P300b belongs to the family of the late posterior positivities (LPPs) which are closely related to the consciousness of the meaning of the stimulus in the task for the participants themselves (e.g., the: I am seeing the target stimulus for which I have to respond). The fragmentation of the self present in schizophrenia, could thus be the cause. If this were true, then P300bs should be somewhat reduced in healthy participants when their self representations are temporarily and minimally fragmented. We tested this hypothesis by using the innocuous fragmentation of the self that occurs in virtual reality (VR). There, participants can have a fragment of their self in an avatar they feel embodied in, within a VR room, while having another fragment of their self in their real body in the real room where they know they are. Our participants were thus equipped with a head mounted display in which they viewed a virtual room where a female humanoid avatar was facing them. She was lifting her right hand in synchrony with the participants, in order to induce in them a feeling of embodiment. Stimuli were a frequent green- and a rare red-disk, the oddball stimulus, occurring over the right hand of the avatar. Participants had to perform a Go/NoGo task, lifting their right hand to the frequent green disk and repressing this action for the oddball red disk. In the syncMove block of trials the avatar was lifting her right hand synchronously with the participant, disturbing her self representation as confirmed by the debriefing session. In the noMove block, the avatar remained immobile. In the classic block, only the red and the green disk were displayed on a monochrome background, neither the room nor the avatar were shown. As predicted, P300bs were found to be smaller in the syncMove block than in the noMove- and the classic-block in participants who had the classically large P300b oddball effect between ERPs to the frequent and those to the rare stimuli. Reduced P300bs of schizophrenia could thus be partly due to self fragmentation. Results may also open an avenue of research to the functional significance of LPPs and the content of the consciousness indexed by these potentials.

Patterns of activation and de-activation associated with cue-guided spatial navigation: A whole-brain, voxel-based study.

Functional imaging studies have implicated the hippocampus and parahippocampal gyrus in cue-guided spatial navigation, but also many other regions. Furthermore, little is known about de-activations that take place during performance of navigation tasks, something that is of interest given that the hippocampus is a component of the default mode network, which de-activates during attention-demanding tasks. In this study 22 healthy subjects underwent whole-brain functional Magnetic Resonance Imaging (fMRI) while they navigated toward a previously learned goal in a virtual reality environment. At a threshold of p<0.05 corrected, the subjects showed a pattern of widespread cortical activations, including the parahippocampal and retrosplenial cortex and also parts of the frontal, temporal and occipital cortex. Hippocampal activation, however, was restricted to the posterior portion of the structure bilaterally. De-activations were seen in the medial frontal cortex and other regions of the default mode network, but not in the posterior cingulate cortex/precuneus. The findings support the involvement of the hippocampus in cue-guided navigation, but suggest that its posterior regions are particularly important. Cue-guided spatial navigation is associated with de-activation in some but not all parts of the default mode network.

Virtual race transformation reverses racial in-group bias.

People generally show greater preference for members of their own racial group compared to racial out-group members. This type of 'in-group bias' is evident in mimicry behaviors. We tend to automatically mimic the behaviors of in-group members, and this behavior is associated with interpersonal sensitivity and empathy. However, mimicry is reduced when interacting with out-group members. Although race is considered an unchangeable trait, it is possible using embodiment in immersive virtual reality to engender the illusion in people of having a body of a different race. Previous research has used this technique to show that after a short period of embodiment of White people in a Black virtual body their implicit racial bias against Black people diminishes. Here we show that this technique powerfully enhances mimicry. We carried out an experiment with 32 White (Caucasian) female participants. Half were embodied in a White virtual body and the remainder in a Black virtual body. Each interacted in two different sessions with a White and a Black virtual character, in counterbalanced order. The results show that dyads with the same virtual body skin color expressed greater mimicry than those of different color. Importantly, this effect occurred depending on the virtual body's race, not participants' actual racial group. When embodied in a Black virtual body, White participants treat Black as their novel in-group and Whites become their novel out-group. This reversed in-group bias effect was obtained regardless of participants' level of implicit racial bias. We discuss the theoretical and practical implications of this surprising psychological phenomenon.

Examining hippocampal function in schizophrenia using a virtual reality spatial navigation task.

BACKGROUND: Structural pathology in the hippocampus is well-documented in schizophrenia, but brain functional changes have not been consistently found. We used spatial navigation in a virtual reality environment, a task that is known to produce robust hippocampal activation in healthy subjects, to examine task-related activations and de-activations in the disorder. METHODS: Twenty-seven DSM IV schizophrenia patients and 32 healthy controls underwent fMRI while they navigated to a goal through a virtual reality town. Activations and de-activations were examined at the whole brain level and also using a region-of-interest (ROI) in the hippocampus. RESULTS: Spatial navigation was associated with activation in the posterior hippocampus and parahippocampal gyrus plus widespread neocortical areas. The patients showed reduced activation compared to the controls in the left dorsolateral prefrontal cortex (DLPFC) and the left occipital/temporal cortex. No differences in hippocampal activation were seen either at the whole-brain level or in the ROI analysis. The patients showed failure of de-activation affecting some but not all subregions of the default mode network. CONCLUSIONS: Schizophrenia is associated with task-related hypoactivation in the DLPFC during spatial navigation, but not with functional changes in the hippocampus. The failure of de-activation also found adds to evidence for default mode network dysfunction in the disorder.

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.

Beaming into the rat world: enabling real-time interaction between rat and human each at their own scale.

Immersive virtual reality (IVR) typically generates the illusion in participants that they are in the displayed virtual scene where they can experience and interact in events as if they were really happening. Teleoperator (TO) systems place people at a remote physical destination embodied as a robotic device, and where typically participants have the sensation of being at the destination, with the ability to interact with entities there. In this paper, we show how to combine IVR and TO to allow a new class of application. The participant in the IVR is represented in the destination by a physical robot (TO) and simultaneously the remote place and entities within it are represented to the participant in the IVR. Hence, the IVR participant has a normal virtual reality experience, but where his or her actions and behaviour control the remote robot and can therefore have physical consequences. Here, we show how such a system can be deployed to allow a human and a rat to operate together, but the human interacting with the rat on a human scale, and the rat interacting with the human on the rat scale. The human is represented in a rat arena by a small robot that is slaved to the human's movements, whereas the tracked rat is represented to the human in the virtual reality by a humanoid avatar. We describe the system and also a study that was designed to test whether humans can successfully play a game with the rat. The results show that the system functioned well and that the humans were able to interact with the rat to fulfil the tasks of the game. This system opens up the possibility of new applications in the life sciences involving participant observation of and interaction with animals but at human scale.

Visual realism enhances realistic response in an immersive virtual environment--part 2.

Does realistic lighting in an immersive VR application enhance presence--that is, the participants' feeling that they're actually in the scene and behaving accordingly? Part 1 of this study indicated that presence is more likely with real-time ray tracing than with ray casting. However, that research couldn't separate the effects of overall illumination quality from the dynamic effects of real-time shadows and reflections. In a new experiment, 20 people experienced a scene rendered with either global or local illumination. Both conditions included dynamically changing shadows and reflections. Illumination quality didn't affect presence, so the earlier result must have been caused by dynamic shadows and reflections. Nevertheless, global illumination did result in greater plausibility--that is, participants were more likely to respond as if the virtual events were real. These results indicate that global illumination does affect participant responses and is worth the effort.

Multisensory stimulation can induce an illusion of larger belly size in immersive virtual reality.

BACKGROUND: Body change illusions have been of great interest in recent years for the understanding of how the brain represents the body. Appropriate multisensory stimulation can induce an illusion of ownership over a rubber or virtual arm, simple types of out-of-the-body experiences, and even ownership with respect to an alternate whole body. Here we use immersive virtual reality to investigate whether the illusion of a dramatic increase in belly size can be induced in males through (a) first person perspective position (b) synchronous visual-motor correlation between real and virtual arm movements, and (c) self-induced synchronous visual-tactile stimulation in the stomach area. METHODOLOGY: Twenty two participants entered into a virtual reality (VR) delivered through a stereo head-tracked wide field-of-view head-mounted display. They saw from a first person perspective a virtual body substituting their own that had an inflated belly. For four minutes they repeatedly prodded their real belly with a rod that had a virtual counterpart that they saw in the VR. There was a synchronous condition where their prodding movements were synchronous with what they felt and saw and an asynchronous condition where this was not the case. The experiment was repeated twice for each participant in counter-balanced order. Responses were measured by questionnaire, and also a comparison of before and after self-estimates of belly size produced by direct visual manipulation of the virtual body seen from the first person perspective. CONCLUSIONS: The results show that first person perspective of a virtual body that substitutes for the own body in virtual reality, together with synchronous multisensory stimulation can temporarily produce changes in body representation towards the larger belly size. This was demonstrated by (a) questionnaire results, (b) the difference between the self-estimated belly size, judged from a first person perspective, after and before the experimental manipulation, and (c) significant positive correlations between these two measures. We discuss this result in the general context of body ownership illusions, and suggest applications including treatment for body size distortion illnesses.

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.

First person experience of body transfer in virtual reality.

BACKGROUND: Altering the normal association between touch and its visual correlate can result in the illusory perception of a fake limb as part of our own body. Thus, when touch is seen to be applied to a rubber hand while felt synchronously on the corresponding hidden real hand, an illusion of ownership of the rubber hand usually occurs. The illusion has also been demonstrated using visuomotor correlation between the movements of the hidden real hand and the seen fake hand. This type of paradigm has been used with respect to the whole body generating out-of-the-body and body substitution illusions. However, such studies have only ever manipulated a single factor and although they used a form of virtual reality have not exploited the power of immersive virtual reality (IVR) to produce radical transformations in body ownership. PRINCIPAL FINDINGS: Here we show that a first person perspective of a life-sized virtual human female body that appears to substitute the male subjects' own bodies was sufficient to generate a body transfer illusion. This was demonstrated subjectively by questionnaire and physiologically through heart-rate deceleration in response to a threat to the virtual body. This finding is in contrast to earlier experimental studies that assume visuotactile synchrony to be the critical contributory factor in ownership illusions. Our finding was possible because IVR allowed us to use a novel experimental design for this type of problem with three independent binary factors: (i) perspective position (first or third), (ii) synchronous or asynchronous mirror reflections and (iii) synchrony or asynchrony between felt and seen touch. CONCLUSIONS: The results support the notion that bottom-up perceptual mechanisms can temporarily override top down knowledge resulting in a radical illusion of transfer of body ownership. The research also illustrates immersive virtual reality as a powerful tool in the study of body representation and experience, since it supports experimental manipulations that would otherwise be infeasible, with the technology being mature enough to represent human bodies and their motion.

The Use of Virtual Reality in the Study of People's Responses to Violent Incidents.

This paper reviews experimental methods for the study of the responses of people to violence in digital media, and in particular considers the issues of internal validity and ecological validity or generalisability of results to events in the real world. Experimental methods typically involve a significant level of abstraction from reality, with participants required to carry out tasks that are far removed from violence in real life, and hence their ecological validity is questionable. On the other hand studies based on field data, while having ecological validity, cannot control multiple confounding variables that may have an impact on observed results, so that their internal validity is questionable. It is argued that immersive virtual reality may provide a unification of these two approaches. Since people tend to respond realistically to situations and events that occur in virtual reality, and since virtual reality simulations can be completely controlled for experimental purposes, studies of responses to violence within virtual reality are likely to have both ecological and internal validity. This depends on a property that we call 'plausibility' - including the fidelity of the depicted situation with prior knowledge and expectations. We illustrate this with data from a previously published experiment, a virtual reprise of Stanley Milgram's 1960s obedience experiment, and also with pilot data from a new study being developed that looks at bystander responses to violent incidents.

Real-time global illumination for VR applications.

Real-time global illumination in VR systems enhances scene realism by incorporating soft shadows, reflections of objects in the scene, and color bleeding. The Virtual Light Field (VLF) method enables real-time global illumination rendering in VR. The VLF has been integrated with the Extreme VR system for real-time GPU-based rendering in a Cave Automatic Virtual Environment.