First Person Perspective of Seated Participants Over a Walking Virtual Body Leads to Illusory Agency Over the Walking

Agency, the attribution of authorship to an action of our body, requires the intention to carry out the action, and subsequently a match between its predicted and actual sensory consequences. However, illusory agency can be generated through priming of the action together with perception of bodily action, even when there has been no actual corresponding action. Here we show that participants can have the illusion of agency over the walking of a virtual body even though in reality they are seated and only allowed head movements. The experiment (n = 28) had two factors: Perspective (1PP or 3PP) and Head Sway (Sway or NoSway). Participants in 1PP saw a life-sized virtual body spatially coincident with their own from a first person perspective, or the virtual body from third person perspective (3PP). In the Sway condition the viewpoint included a walking animation, but not in NoSway. The results show strong illusions of body ownership, agency and walking, in the 1PP compared to the 3PP condition, and an enhanced level of arousal while the walking was up a virtual hill. Sway reduced the level of agency. We conclude with a discussion of the results in the light of current theories of agency

First person perspective of seated participants over a walking virtual body leads to illusory agency over the walking

Agency, the attribution of authorship to an action of our body, requires the intention to carry out the action, and subsequently a match between its predicted and actual sensory consequences. However, illusory agency can be generated through priming of the action together with perception of bodily action, even when there has been no actual corresponding action. Here we show that participants can have the illusion of agency over the walking of a virtual body even though in reality they are seated and only allowed head movements. The experiment (n = 28) had two factors: Perspective (1PP or 3PP) and Head Sway (Sway or NoSway). Participants in 1PP saw a life-sized virtual body spatially coincident with their own from a first person perspective, or the virtual body from third person perspective (3PP). In the Sway condition the viewpoint included a walking animation, but not in NoSway. The results show strong illusions of body ownership, agency and walking, in the 1PP compared to the 3PP condition, and an enhanced level of arousal while the walking was up a virtual hill. Sway reduced the level of agency. We conclude with a discussion of the results in the light of current theories of agency

The Effects of Visuomotor Calibration to the Perceived Space and Body, through Embodiment in Immersive Virtual Reality

We easily adapt to changes in the environment that involve cross-sensory discrepancies (e.g., between vision and proprioception). Adaptation can lead to changes in motor commands so that the experienced sensory consequences are appropriate for the new environment (e.g., we program a movement differently while wearing prisms that shift our visual space). In addition to these motor changes, perceptual judgments of space can also be altered (e.g., how far can I reach with my arm?). However, in previous studies that assessed perceptual judgments of space after visuomotor adaptation, the manipulation was always a planar spatial shift, whereas changes in body perception could not directly be assessed. In this study, we investigated the effects of velocity-dependent (spatiotemporal) and spatial scaling distortions of arm movements on space and body perception, taking advantage of immersive virtual reality. Exploiting the perceptual illusion of embodiment in an entire virtual body, we endowed subjects with new spatiotemporal or spatial 3D mappings between motor commands and their sensory consequences. The results imply that spatiotemporal manipulation of 2 and 4 times faster can significantly change participants’ proprioceptive judgments of a virtual object’s size without affecting the perceived body ownership, although it did affect the agency of the movements. Equivalent spatial manipulations of 11 and 22 degrees of angular offset also had a significant effect on the perceived virtual object’s size; however, the mismatched information did not affect either the sense of body ownership or agency. We conclude that adaptation to spatial and spatiotemporal distortion can similarly change our perception of space, although spatiotemporal distortions can more easily be detected

Shared neurocognitive mechanisms of attenuating self-touch and illusory self-touch

Despite the fact that any successful achievement of willed actions necessarily entails the sense of body ownership (the feeling of owning the moving body parts), it is still unclear how this happens. To address this issue at both behavioral and neural levels, we capitalized on sensory attenuation (SA) phenomenon (a self-generated stimulus is perceived as less intense than an identical externally generated stimulus). We compared the intensity of somatosensory stimuli produced by one's own intended movements and by movements of an embodied fake hand. Then, we investigated if in these two conditions SA was equally affected by interfering with the activity of the supplementary motor area (SMA; known to be related to motor intention and SA) using single-pulse transcranial magnetic stimulation. We showed that ownership of the fake hand triggered attenuation of somatosensory stimuli generated by its movements that were comparable to the attenuation of self-generated stimuli. Furthermore, disrupting the SMA eliminated the SA effect regardless of whether it was triggered by actual participant's movements or by illusory ownership. Our findings suggest that SA triggered by body ownership relies, at least in part, on the activation of the same brain structures as SA triggered by motor-related signals

Embodying compassion: A virtual reality paradigm for overcoming excessive self-criticism

Virtual reality has been successfully used to study and treat psychological disorders such as phobias and posttraumatic stress disorder but has rarely been applied to clinically-relevant emotions other than fear and anxiety. Self-criticism is a ubiquitous feature of psychopathology and can be treated by increasing levels of self-compassion. We exploited the known effects of identification with a virtual body to arrange for healthy female volunteers high in self-criticism to experience self-compassion from an embodied first-person perspective within immersive virtual reality. Whereas observation and practice of compassionate responses reduced self-criticism, the additional experience of embodiment also increased self-compassion and feelings of being safe. The results suggest potential new uses for immersive virtual reality in a range of clinical conditions.N/

Psychometrics of Disembodiment and Its Differential Modulation by Visuomotor and Visuotactile Mismatches

Altered states of embodiment are fundamental to the scientific understanding of bodily self consciousness. The feeling of disembodiment during everyday activities is common to clinical conditions; however, the direct study of disembodiment in experimental setups is rare compared to the extensive investigation of illusory embodiment of an external object. Using mixed reality to modulate embodiment through temporally mismatching sensory signals from the own body, we assessed how such mismatches affect phenomenal and physiological aspects of embodiment and measured perceptual thresholds for these across multimodal signals. The results of a principal component analysis suggest that multimodal mismatches generally induce disembodiment by increasing the sense of disownership and deafference and decreasing embodiment; however, this was not generally reflected in physiological changes. Although visual delay decreased embodiment both during active movement and passive touch, the effect was stronger for the former. We discuss the relevance of these findings for understanding bodily self plasticity

Learning empathy through virtual reality : Multiple strategies for training empathy-related abilities using body ownership Illusions in embodied virtual reality

Several disciplines have investigated the interconnected empathic abilities behind the proverb “to walk a mile in someone else’s shoes” to determine how the presence, and absence, of empathy-related phenomena affect prosocial behavior and intergroup relations. Empathy enables us to learn from others’ pain and to know when to offer support. Similarly, virtual reality (VR) appears to allow individuals to step into someone else’s shoes, through a perceptual illusion called embodiment, or the body ownership illusion. Considering these perspectives, we propose a theoretical analysis of different mechanisms of empathic practices in order to define a possible framework for the design of empathic training in VR. This is not intended to be an extensive review of all types of practices, but an exploration of empathy and empathy-related phenomena. Empathy-related training practices are analyzed and categorized. We also identify different variables used by pioneer studies in VR to promote empathy-related responses. Finally, we propose strategies for using embodied VR technology to train specific empathy-related abilities

Characterizing first and third person viewpoints and their alternation for embodied interaction in virtual reality

Empirical research on the bodily self has shown that the body representation is malleable, and prone to manipulation when conflicting sensory stimuli are presented. Using Virtual Reality (VR) we assessed the effects of manipulating multisensory feedback (full body control and visuo-tactile congruence) and visual perspective (first and third person perspective) on the sense of embodying a virtual body that was exposed to a virtual threat. We also investigated how subjects behave when the possibility of alternating between first and third person perspective at will was presented. Our results support that illusory ownership of a virtual body can be achieved in both first and third person perspectives under congruent visuo-motor-tactile condition. However, subjective body ownership and reaction to threat were generally stronger for first person perspective and alternating condition than for third person perspective. This suggests that the possibility of alternating perspective is compatible with a strong sense of embodiment, which is meaningful for the design of new embodied VR experiences

As light as your scent: effects of smell and sound on body image perception

How people mentally represent their body appearance (i.e., body image perception - BIP) does not always match their actual body. BIP distortions can lead to a detriment in physical and emotional health. Recent works in HCI have shown that technology can be used to change people’s BIP through visual, tactile, proprioceptive, and auditory stimulation. This paper investigates, for the first time, the effect of olfactory stimuli, by looking at a possible enhancement of a known auditory effect on BIP.We present two studies building on emerging knowledge in the field of crossmodal correspondences. First, we explored the correspondences between scents and body shapes. Then, we investigated the impact of combined scents and sounds on one’s own BIP. Our results show that scent stimuli can be used to make participants feel lighter or heavier (i.e., using lemon or vanilla) and to enhance the effect of sound on perceived body lightness. We discuss how these findings can inform future research and design directions to overcome body misperception and create novel augmented and embodied experiences