The Sense of embodiment in virtual reality

What does it feel like to own, to control, and to be inside a body? The multidimensional nature of this experience together with the continuous presence of one's biological body, render both theoretical and experimental approaches problematic. Nevertheless, exploitation of immersive virtual reality has allowed a reframing of this question to whether it is possible to experience the same sensations towards a virtual body inside an immersive virtual environment as toward the biological body, and if so, to what extent. The current paper addresses these issues by referring to the Sense of Embodiment (SoE). Due to the conceptual confusion around this sense, we provide a working definition which states that SoE consists of three subcomponents: the sense of self-location, the sense of agency, and the sense of body ownership. Under this proposed structure, measures and experimental manipulations reported in the literature are reviewed and related challenges are outlined. Finally, future experimental studies are proposed to overcome those challenges, toward deepening the concept of SoE and enhancing it in virtual applications

Illusory ownership of a virtual child body causes overestimation of object sizes and implicit attitude changes

An illusory sensation of ownership over a surrogate limb or whole body can be induced through specific forms of multisensory stimulation, such as synchronous visuotactile tapping on the hidden real and visible rubber hand in the rubber hand illusion. Such methods have been used to induce ownership over a manikin and a virtual body that substitute the real body, as seen from firstperson perspective, through a head-mounted display. However, the perceptual and behavioral consequences of such transformed body ownership have hardly been explored. In Exp. 1, immersive virtual reality was used to embody 30 adults as a 4-y-old child (condition C), and as an adult body scaled to the same height as the child (condition A), experienced from the first-person perspective, and with virtual and real body movements synchronized. The result was a strong body-ownership illusion equally for C and A. Moreover there was an overestimation of the sizes of objects compared with a nonembodied baseline, which was significantly greater for C compared with A. An implicit association test showed that C resulted in significantly faster reaction times for the classification of self with child-like compared with adult-like attributes. Exp. 2 with an additional 16 participants extinguished the ownership illusion by using visuomotor asynchrony, with all else equal. The size-estimation and implicit association test differences between C and A were also extinguished. We conclude that there are perceptual and probably behavioral correlates of bodyownership illusions that occur as a function of the type of body in which embodiment occurs

Erg-O: ergonomic optimization of immersive virtual environments

Interaction in VR involves large body movements, easily inducing fatigue and discomfort. We propose Erg-O, a manipulation technique that leverages visual dominance to maintain the visual location of the elements in VR, while making them accessible from more comfortable locations. Our solution works in an open-ended fashion (no prior knowledge of the object the user wants to touch), can be used with multiple objects, and still allows interaction with any other point within user's reach. We use optimization approaches to compute the best physical location to interact with each visual element, and space partitioning techniques to distort the visual and physical spaces based on those mappings and allow multi-object retargeting. In this paper we describe the Erg-O technique, propose two retargeting strategies and report the results from a user study on 3D selection under different conditions, elaborating on their potential and application to specific usage scenarios

Illusory ownership of a virtual child body causes overestimation of object sizes and implicit attitude changes

An illusory sensation of ownership over a surrogate limb or whole body can be induced through specific forms of multisensory stimulation, such as synchronous visuotactile tapping on the hidden real and visible rubber hand in the rubber hand illusion. Such methods have been used to induce ownership over a manikin and a virtual body that substitute the real body, as seen from firstperson perspective, through a head-mounted display. However, the perceptual and behavioral consequences of such transformed body ownership have hardly been explored. In Exp. 1, immersive virtual reality was used to embody 30 adults as a 4-y-old child (condition C), and as an adult body scaled to the same height as the child (condition A), experienced from the first-person perspective, and with virtual and real body movements synchronized. The result was a strong body-ownership illusion equally for C and A. Moreover there was an overestimation of the sizes of objects compared with a nonembodied baseline, which was significantly greater for C compared with A. An implicit association test showed that C resulted in significantly faster reaction times for the classification of self with child-like compared with adult-like attributes. Exp. 2 with an additional 16 participants extinguished the ownership illusion by using visuomotor asynchrony, with all else equal. The size-estimation and implicit association test differences between C and A were also extinguished. We conclude that there are perceptual and probably behavioral correlates of bodyownership illusions that occur as a function of the type of body in which embodiment occurs

Shared Decision Making in a Collaborative Task with Reciprocal Haptic Feedback - an Efficiency-Analysis

Abstract — When robots leave industrial settings, they have to be designed allowing intuitive communication with the humans they interact with. The current paper focuses on collaboration in kinesthetic tasks. Herein, we investigate decision situations. This way, the need of communication between partners can be addressed. The current paper introduces for the first time an experimental paradigm which allows studying the effect of decision making in haptic collaboration. Because reciprocal haptic feedback is challenging to provide, we analyze its efficiency in human-human collaboration to understand when it is worth to invest in this additional modality. A one degree of tracking experiment with two human partners revealed that the additional physical effort accompanying reciprocal haptic feedback is directly transformed into higher performance (compared to a control condition without reciprocal haptic feedback). Thus, the presented results motivate further research on the nature of the haptic negotiation between human partners to achieve the same performance benefits in kinesthetic collaboration with robotic partners. I

Control-theoretic Model of Haptic Human-Human Interaction in a Pursuit Tracking Task

Abstract — Achieving natural and intuitive interaction is one of the main challenges in physical human-robot interaction. We approach this challenge by modeling haptic human-human interaction with the final goal of transferring found relationships to human-robot interaction. The focus of this paper is on two human operators performing collaboratively a joint object manipulation, i.e. a pursuit tracking task. McRuer’s crossover model is a well established method to describe the behavior of one human operator performing such a task. In this paper, we extent McRuer’s approach to two human operators performing the task collaboratively. Results based on experimetally gained data show that the interacting partners adapt their behavior to each other and to the task in such a way that the crossover model can still be applied to the interacting dyad. It is also shown that the individual’s behavior changes when interacting with a partner in contrast to performing the task alone. I

Development and evaluation of a device for the haptic rendering of rotatory car doors

Virtual prototyping of car doors enhanced with haptic feedback is a promising way to decrease the number of physical prototypes. We clarify, correct, summarize, and extend our previous work on the haptic simulation of car doors. A fundamental issue is the derivation of the performance specification of a task-optimized haptic interface, which is based on the knowledge of the typical user interaction with a car door and a comprehensive model of the dynamics of a rotatory car door. We reason that a direct drive with a high torque output (≥ 100 N·m) and a high control bandwidth has to be used. Consequently, we created a backlash-free very stiff device providing a safe and high-fidelity haptic rendering. Finally, we conducted an extensive user study with 17 participants. An important result is that the haptic simulation can be reliably used to evaluate different door concepts if the difference between them is larger than 5 N·m. Furthermore, the participants did not like a high effort for closing the door, while both a low and a medium effort are appreciated. This is in accordance with the heuristic findings of the automotive industry, which shows the effectiveness of our virtual prototyping approach. © 2009 IEEE

Predictability of a Human Partner in a Pursuit Tracking Task without Haptic Feedback

We are interested in whether humans create a model of their partner when they jointly manipulate an object in a virtual task without haptic feedback. In such a scenario the partner is perceived as a disturbance because she/he is responsible for inconsistencies between the visual and proprioceptive feedback of the individual. To gain basic knowledge on the predictability of such disturbances we compare a pre-recorded human partner with predictable (time delay) and unpredictable (random) disturbances and two additional control conditions in a pursuit tracking task. Results indicate that the influence of the pre-recorded partner is partly predictable, therefore we assume that a model of the partner’s behavior is built by the human.