Owning an overweight or underweight body: distinguishing the physical, experienced and virtual body

Our bodies are the most intimately familiar objects we encounter in our perceptual environment. Virtual reality provides a unique method to allow us to experience having a very different body from our own, thereby providing a valuable method to explore the plasticity of body representation. In this paper, we show that women can experience ownership over a whole virtual body that is considerably smaller or larger than their physical body. In order to gain a better understanding of the mechanisms underlying body ownership, we use an embodiment questionnaire, and introduce two new behavioral response measures: an affordance estimation task (indirect measure of body size) and a body size estimation task (direct measure of body size). Interestingly, after viewing the virtual body from first person perspective, both the affordance and the body size estimation tasks indicate a change in the perception of the size of the participant’s experienced body. The change is biased by the size of the virtual body (overweight or underweight). Another novel aspect of our study is that we distinguish between the physical, experienced and virtual bodies, by asking participants to provide affordance and body size estimations for each of the three bodies separately. This methodological point is important for virtual reality experiments investigating body ownership of a virtual body, because it offers a better understanding of which cues (e.g. visual, proprioceptive, memory, or a combination thereof) influence body perception, and whether the impact of these cues can vary between different setups

Phenomenal regression to the real object in physical and virtual worlds

© 2014, Springer-Verlag London. In this paper, we investigate a new approach to comparing physical and virtual size and depth percepts that captures the involuntary responses of participants to different stimuli in their field of view, rather than relying on their skill at judging size, reaching or directed walking. We show, via an effect first observed in the 1930s, that participants asked to equate the perspective projections of disc objects at different distances make a systematic error that is both individual in its extent and comparable in the particular physical and virtual setting we have tested. Prior work has shown that this systematic error is difficult to correct, even when participants are knowledgeable of its likelihood of occurring. In fact, in the real world, the error only reduces as the available cues to depth are artificially reduced. This makes the effect we describe a potentially powerful, intrinsic measure of VE quality that ultimately may contribute to our understanding of VE depth compression phenomena

Can virtual reality predict body part discomfort and performance of people in realistic world for assembling tasks?

This paper presents our work on relationship of evaluation results between virtual environment (VE) and realistic environment (RE) for assembling tasks. Evaluation results consist of subjective results (BPD and RPE) and objective results (posture and physical performance). Same tasks were performed with same experimental configurations and evaluation results were measured in RE and VE respectively. Then these evaluation results were compared. Slight difference of posture between VE and RE was found but not great difference of effect on people according to conventional ergonomics posture assessment method. Correlation of BPD and performance results between VE and RE are found by linear regression method. Moreover, results of BPD, physical performance, and RPE in VE are higher than that in RE with significant difference. Furthermore, these results indicates that subjects feel more discomfort and fatigue in VE than RE because of additional effort required in VE

Perception and Emotion in Virtual Reality: The Role of the Body and the Contribution of Presence

This thesis reports four studies in the context of virtual reality (VR), feelings of presence, emotion, and perception. Previous research established the existence of cross-dimensional perceptual interrelations such as the interconnection between experienced motion and subjective time. This is thought to result from a common perceptual system. However, the specifics of this system are a matter of ongoing research. An important binding factor between perceptual dimensions is the bodily self, which was described as a reference for perception. In Study I, manipulations of the size of a virtual self-representation were shown to affect the spatial judgment of objects. In Study II, the degree of self-motion in an immersive virtual environment (IVE) influenced the subjective perception of time, corroborating previous findings about the common perceptual system. Besides the virtual self-representation, there is another important variable in VR experiments: Presence is described as the feeling of being in a mediated environment. Presence was not associated with improved performance in the spatial and temporal judgments of Studies I and II. However, in Study III, presence in a gaming activity was linked to improved mood after an experimental stress-induction. This especially applied to VR gaming, where impressions about the subjective realism of the IVE might have been crucial for mood repair. As outlined in Study IV, it is important to distinguish between presence as an attentional allocation to the mediated world and as an individual judgment about its realism. Taken together, the results from all studies corroborate the idea of the self as a fundamental perceptual reference, confirm results about the psychological connection between space and time, emphasize the benefits of VR gaming in improving mood, and elucidate the role of perceived realism in assessing presence in IVEs

Enhancing Perception and Immersion in Pre-Captured Environments through Learning-Based Eye Height Adaptation

Pre-captured immersive environments using omnidirectional cameras provide a wide range of virtual reality applications. Previous research has shown that manipulating the eye height in egocentric virtual environments can significantly affect distance perception and immersion. However, the influence of eye height in pre-captured real environments has received less attention due to the difficulty of altering the perspective after finishing the capture process. To explore this influence, we first propose a pilot study that captures real environments with multiple eye heights and asks participants to judge the egocentric distances and immersion. If a significant influence is confirmed, an effective image-based approach to adapt pre-captured real-world environments to the user's eye height would be desirable. Motivated by the study, we propose a learning-based approach for synthesizing novel views for omnidirectional images with altered eye heights. This approach employs a multitask architecture that learns depth and semantic segmentation in two formats, and generates high-quality depth and semantic segmentation to facilitate the inpainting stage. With the improved omnidirectional-aware layered depth image, our approach synthesizes natural and realistic visuals for eye height adaptation. Quantitative and qualitative evaluation shows favorable results against state-of-the-art methods, and an extensive user study verifies improved perception and immersion for pre-captured real-world environments.Comment: 10 pages, 13 figures, 3 tables, submitted to ISMAR 202

Embodiment and the Self: using Virtual Reality and Full Body Illusion to change bodily self-representation, perception and behaviour

Virtual Reality (VR) is an important tool for researchers of many different fields, from cognitive neuroscience to social psychology. The present work will explore the use of VR, and in particular of immersive virtual reality (IVR), in the study of some key aspects of our bodily self and bodily related behaviour and perception. In the first part of the present work we will discuss the combined used of IVR and full body illusion (FBI) in the study of body image distortion (BID) in anorexia nervosa (AN). The first chapter will serve as a general introduction to AN and its most prominent clinical characteristics, as well as introducing some key concepts like the malleability of the bodily-self through multisensory bodily illusions and a brief overview of a series of studies that applied both IVR and embodiment illusions to manipulate participants’ body representation. The second chapter will present a study in which we used the embodiment illusion of different sized avatars to characterize and reduce both the perceptual (body overestimation) and cognitive-emotional (body dissatisfaction) components of BID in AN. For this study we built personalized avatars for each participants (healthy controls (HC) and AN patients) and applied synchronous and asynchronous interpersonal multisensory stimulation (IMS) to three different virtual bodies (the perceived one, a +15% fatter one and a -15% thinner one). The different components of BID were measured by asking participants to choose the body that best resembled their real and ideal body before and after the embodiment illusion was induced. The results of this study showed a higher body dissatisfaction in AN patients, who also reported stronger negative emotions after being exposed to the largest avatar. However, the embodiment procedure did not affect BID in AN patients. Based on the results of the previous study, in the study presented in the third chapter we decided to shift our focus from somatorepresentation, i.e. the explicit representation of the body which comprise both cognitive and emotional components of body image, to somatoperception, i.e. the implicit representation of the body which comprise both body perception and body schema. In this study we applied a FBI over an underweight (BMI = 15) and normal weight (BMI = 19) avatar and measured the effect of the embodiment illusion on participants’ (AN and HC) body perception and body schema estimations. To measure body perception, we asked participants to estimate the width of their hips while their vision was blocked, whereas for the body schema estimation participants had to estimate the minimum door’s aperture width in order to pass through it inside an IVR scenario. The results showed that AN patients reported an overestimation in both body perception and body schema estimations. Furthermore, in AN patients we saw a change in the body schema estimation accordingly to the size of the embodied avatar, thus showing a higher bodily self-plasticity compared to HC. In the fourth chapter of the present work we will go over the results of the two aforementioned studies and will briefly discuss some possible future directions. Finally, the last two chapters of the thesis will present two research projects that will respectively utilize IVR and the embodiment illusion for the study of individual dishonest behaviour in digital interactions (chapter 5) and for the modulation of acute and chronic pain (chapter 6). As the COVID-19 pandemic deeply affected the work on both these studies, these two final chapters will only present a general introduction and the methods/technical implementation for both research projects

Movement, Action, and Situation: Presence in Virtual Environments

Presence is commonly defined as the subjective feeling of "being there". It has been mainly conceived of as deriving from immersion, interaction, and social and narrative involvement with suitable technology. We argue that presence depends on a suitable integration of aspects relevant to an agent's movement and perception, to her actions, and to her conception of the overall situation in which she finds herself, as well as on how these aspects mesh with the possibilities for action afforded in the interaction with the virtual environment

Expectations and Beliefs in Immersive Virtual Reality Environments: Managing of Body Perception

Real and Perceived Feet Orientation Under Fatiguing and Non-Fatiguing Conditions in an Immersive Virtual Reality Environment ABSTRACT Lower limbs position sense is a complex yet poorly understood mechanism, influenced by many factors. Hence, we investigated the position sense of lower limbs through feet orientation with the use of Immersive Virtual Reality (IVR). Participants had to indicate how they perceived the real 1050 orientation of their feet by orientating a virtual representation of the feet that was shown in an IVR 1051 scenario. We calculated the angle between the two virtual feet (α-VR) after a high-knee step-in-1052 place task. Simultaneously, we recorded the real angle between the two feet (α-R) (T1). Hence, we 1053 assessed if the acute fatigue impacted the position sense. The same procedure was repeated after 1054 inducing muscle fatigue (T2) and after 10 minutes from T2 (T3). Finally, we also recorded the time 1055 needed to confirm the perceived position before and after the acute fatigue protocol. Thirty healthy 1056 adults (27.5 ± 3.8: 57% female, 43% male) were immersed in an IVR scenario with a representation 1057 of two feet. We found a mean difference between α-VR and α-R of 20.89° [95% CI: 14.67°, 27.10°] 1058 in T1, 16.76° [9.57°, 23.94°] in T2, and 16.34° [10.00°, 22.68°] in T3. Participants spent 12.59, 17.50 1059 and 17.95 seconds confirming the perceived position of their feet at T1, T2, T3, respectively. 1060 Participants indicated their feet as forwarding parallel though divergent, showing a mismatch in the 1061 perceived position of feet. Fatigue seemed not to have an impact on position sense but delayed the 1062 time to accomplish this task.The Effect of Context on Eye-Height Estimation in Immersive Virtual Reality: a Cross-Sectional Study ABSTRACT Eye-height spatial perception provides a reference to scale the surrounding environment. It is the result of the integration of visual and postural information. When these stimuli are discordant, the perceived spatial parameters are distorted. Previous studies in immersive virtual reality (IVR) showed that spatial perception is influenced by the visual context of the environment. Hence, this study explored how manipulating the context in IVR affects individuals’ eye-height estimation. Two groups of twenty participants each were immersed in two different IVR environments, represented by a closed room (Wall - W) and an open field (No Wall - NW). Under these two different conditions, participants had to adjust their virtual perspective, estimating their eye height. We calculated the perceived visual offset as the difference between virtual and real eye height, to assess whether the scenarios and the presence of virtual shoes (Feet, No Feet) influenced participants’ estimates at three initial offsets (+100 cm, +0 cm, -100 cm). We found a mean difference between the visual 1679 offsets registered in those trials that started with 100 cm and 0 cm offsets (17.24 cm [8.78; 25.69]) 1680 and between 100 cm and -100 cm offsets (22.35 cm [15.65; 29.05]). Furthermore, a noticeable mean difference was found between the visual offsets recorded in group W, depending on the presence or absence of the virtual shoes (Feet VS No Feet: -6.12 [-10.29, -1.95]). These findings describe that different contexts influenced eye-height perception.Positive Expectations led to Motor Improvement: an Immersive Virtual Reality Pilot Study ABSTRACT This pilot study tested the feasibility of an experimental protocol that evaluated the effect of different positive expectations (verbal and visual-haptic) on anterior trunk flexion. Thirty-six participants were assigned to 3 groups (G0, G+ and G++) that received a sham manoeuvre while immersed in Immersive Virtual Reality (IVR). In G0, the manouvre was paired with by neutral verbal statement. In G+ and G++ the manouvre was paired with a positive verbal statement, but only G++ received a visual-haptic illusion. The illusion consisted of lifting a movable tile placed in front of the participants, using its height to raise the floor level in virtual reality. In this way, participants experienced the perception of touching the floor, through the tactile and the virtual visual afference. The distance between fingertips and the floor was measured before, immediately after, and after 5 minutes from the different manouvres. A major difference in anterior trunk flexion was found for G++ compared to the other groups, although it was only significant compared to G0. This result highlighted the feasibility of the present study for future research on people with mobility limitations (e.g., low back pain or kinesiophobia) and the potential role of a visual-haptic illusion in modifying the performance of trunk flexion