Search Results (9)

The full-body illusion (FBI) is a phenomenon where individuals experience body perception not in their physical body but in an external virtual body. Previous studies have shown that the relationship between the self and the virtual body influences the occurrence and intensity of the FBI. However, the influence of interpersonal factors on the FBI has not been explored. This study investigated the effect of interpersonal synchrony on body perception through an evaluation experiment involving the FBI. Specifically, the participant and an experimenter clapped together while their movements were recorded by a video camera placed behind the participant and displayed to them via a head-mounted display (HMD). This setup presented synchronous visuotactile stimuli, aligning the visual feedback with the tactile sensations in the participant’s hands, to induce the FBI. The experimenter’s clapping rhythm was manipulated to either be synchronous or asynchronous with the participant’s rhythm, thus controlling the state of movement synchronization between the participant and the experimenter. The impact on the participant’s body perception was then assessed through subjective reports. The results indicated that when the clapping rhythm was synchronized with the other person, there was a significant reduction in touch referral to the participant’s virtual body. Additionally, there was a trend toward a reduction in ownership. This study demonstrated for the first time that interpersonal synchrony affects body perception. Full article

Force-feedback devices enhance task performance in most robot teleoperations. However, their increased size with additional degrees of freedom can limit the robot’s applicability. To address this, an interface that visually presents force feedback is proposed, eliminating the need for bulky physical devices. Our telepresence system renders robotic hands transparent in the camera image while displaying virtual hands. The forces applied to the robot deform these virtual hands. The deformation creates an illusion that the operator’s hands are deforming, thus providing pseudo-haptic feedback. We conducted a weight comparison experiment in a virtual reality environment to evaluate force sensitivity. In addition, we conducted an object touch experiment to assess the speed of contact detection in a robot teleoperation setting. The results demonstrate that our method significantly surpasses conventional pseudo-haptic feedback in conveying force differences. Operators detected object touch 24.7% faster using virtual hand deformation compared to conditions without feedback. This matches the response times of physical force-feedback devices. This interface not only increases the operator’s force sensitivity but also matches the performance of conventional force-feedback devices without physically constraining the operator. Therefore, the interface enhances both task performance and the experience of teleoperation. Full article

Virtual Body Ownership Illusion (Virtual BOI) refers to the perceptual, cognitive, and behavioral changes that occur due to the illusion that a virtual body is one’s own actual body. Recent research has focused on inducing Virtual Body Ownership Illusion (Virtual BOI) using various physical conditions of VR environments such as haptic feedback and 360-degree immersion, among others. The level of Virtual BOI has been recognized as an important factor in VR-based clinical therapy programs where patient immersion is crucial. However, a common issue is the lack of standardized evaluation tools for Virtual BOI, with most experiments relying on ad hoc tools based on experimental conditions or lacking consideration for the physical design elements of VR. This measurement tool was designed to consider the characteristics of recent VR devices, such as haptics and hand tracking, in the design of experiments and questionnaires. The tool is composed of sub-attributes related to VR technology, including Embodiment, Presence, Visuo-tactile, Visuo-proprioceptive, and Visuo-Motor. Based on a review of the existing literature, we hypothesized that the Virtual BOI scores would vary depending on manipulation methods, viewpoints, and haptic conditions. An experiment was conducted with 39 participants, who performed the same task under four different conditions using a virtual hand. Virtual BOI scores were assessed using the evaluation tool developed for this study. The questionnaire underwent CFA, and three items with factor loadings below 0.5 were removed, resulting in a total of 14 items. Each subscale demonstrated high reliability, with Cronbach’s alpha values greater than 0.60. When developing experiments, clinical programs, or VR content related to Virtual BOI, the evaluation tool presented in this study can be used to assess the level of Virtual BOI. Additionally, by considering technological elements such as haptics and hand tracking, VR environments can be designed to enhance the level of Virtual BOI. Full article

This study explores the conventional ‘funneling’ method by introducing two extra locations beyond the virtual reality (VR) controller boundaries, terming it the extended funneling technique. Thirty-two participants engaged in a localization task, with their responses recorded using eye-tracking technology. They were tasked with localizing a virtual ping-pong ball as it bounced both within and outside their virtual hands on a virtual board. Both the experimental and control groups received simultaneous spatial audio and vibrotactile feedback. The experimental group received vibrotactile feedback with extended funneling, while the control group received vibrotactile feedback without funneling for comparison. The results indicate that the experimental group, benefiting from the extended funneling technique, demonstrated a significantly higher accuracy rate (41.79%) in localizing audio–vibrotactile stimuli compared to the control group (28.21%). No significant differences emerged in embodiment or workload scores. These findings highlight the effectiveness of extended funneling for enhancing the localization of sensory stimuli in VR. Full article

Our research team previously identified a weight illusion in which a lifted object feels heavy when it continuously presents a sinusoidal vibration to the fingertips. However, the mechanism underlying this illusion remains unknown. We thus hypothesized that the autonomous grip force adjustment against a vibrating object would be one of the factors underlying the weight illusion. The autonomous grip force adjustment increases the motor outputs of a human hand system, subsequently raising the sense of effort to keep holding the lifted object. The grip forces and perceived heaviness were evaluated using vibratory stimuli with five different frequencies (30 Hz, 60 Hz, 100 Hz, 200 Hz, and 300 Hz) and three different amplitudes (156 $\mathsf{\mu }$m, 177 $\mathsf{\mu }$m, and 203 $\mathsf{\mu }$m). The results showed that the stimuli at lower frequencies or large amplitudes increased the grip forces more and felt heavier than the stimuli at higher frequencies or small amplitudes. Specifically, the 30 Hz stimuli felt the heaviest and increased the grip force the most. An increase in the grip force was positively correlated with the perceived heaviness. These results indicate that vibratory stimuli influence both the grip force and weight perception. Our findings can contribute to developing haptic displays to present virtual heaviness. Full article

We conducted a virtual reality study to explore virtual hand illusion through three levels of appearance (Appearance dimension: realistic vs. pixelated vs. toon hand appearances) and two levels of tactile feedback (Tactile dimension: no tactile vs. tactile feedback). We instructed our participants to complete a virtual assembly task in this study. Immediately afterward, we asked them to provide self-reported ratings on a survey that captured presence and five embodiment dimensions (hand ownership, touch sensation, agency and motor control, external appearance, and response to external stimuli). The results of our study indicate that (1) tactile feedback generated a stronger sense of presence, touch sensation, and response to external stimuli; (2) the pixelated hand appearance provided the least hand ownership and external appearance; and (3) in the presence of the pixelated hand, prior virtual reality experience of participants impacted their agency and motor control and their response to external stimuli ratings. This paper discusses our findings and provides design considerations for virtual reality applications with respect to the realistic appearance of virtual hands and tactile feedback. Full article

Virtual Reality (VR) is a technology that has been used to provide the Mirror Visual Feedback (MVF) illusion to patients with promising results. In the present work, the goal is to design, develop and test a portable VR-based MVF system that monitors behavioral information about the performance of a simple motor task. The developed application runs in a stand-alone VR system and allows the researcher to select the real and virtual hands used to perform the motor task. The system was evaluated with a group of twenty healthy volunteers (12 men and 8 women) with ages between 18 and 66 years. Participants had to repetitively perform a motor task in four different experimental conditions: two mirror conditions (performing real movements with the dominant and with the non-dominant hand) and two non-mirror conditions. A significant effect of the experimental condition on embodiment score (p < 0.001), response time (p < 0.001), performance time (p < 0.001), trajectory length (p < 0.004) and trajectory maximum horizontal deviation (p < 0.001) was observed. Furthermore, a significant effect of the experimental moment (initial, middle and final parts of the training) on the performance time was observed (p < 0.001). These results show that the monitored parameters provide relevant information to evaluate the participant’s task performance in different experimental conditions. Full article

Motor imagery (MI) is widely used to produce input signals for brain–computer interfaces (BCI) due to the similarities between MI-BCI and the planning–execution cycle. Despite its usefulness, MI tasks can be ambiguous to users and MI produces weaker cortical signals than motor execution. Existing MI guidance systems, which have been reported to provide visual guidance for MI and enhance MI, still have limitations: insufficient immersion for MI or poor expandability to MI for another body parts. We propose a guidance system for MI enhancement that can immerse users in MI and will be easy to extend to other body parts and target motions with few physical constraints. To make easily extendable MI guidance system, the virtual hand illusion is applied to the MI guidance system with a motion tracking sensor. MI enhancement was evaluated in 11 healthy people by comparison with another guidance system and conventional motor commands for BCI. The results showed that the proposed MI guidance system produced an amplified cortical signal compared to pure MI (p < 0.017), and a similar cortical signal as those produced by both actual execution (p > 0.534) and an MI guidance system with the rubber hand illusion (p > 0.722) in the contralateral region. Therefore, we believe that the proposed MI guidance system with the virtual hand illusion is a viable alternative to existing MI guidance systems in various applications with MI-BCI. Full article

“Out of the body” tactile illusion refers to the phenomenon in which one can perceive tactility as if emanating from a location external to the body without any stimulator present there. Taking advantage of such a tactile illusion is one way to provide and realize richer interaction feedback without employing and placing actuators directly at all stimulation target points. However, to further explore its potential, it is important to better understand the underlying physiological and neural mechanism. As such, we measured the brain wave patterns during such tactile illusion and mapped out the corresponding brain activation areas. Participants were given stimulations at different levels with the intention to create veridical (i.e., non-illusory) and phantom sensations at different locations along an external hand-held virtual ruler. The experimental data and analysis indicate that both veridical and illusory sensations involve, among others, the parietal lobe, one of the most important components in the tactile information pathway. In addition, we found that as for the illusory sensation, there is an additional processing resulting in the delay for the ERP (event-related potential) and involvement by the limbic lobe. These point to regarding illusion as a memory and recognition task as a possible explanation. The present study demonstrated some basic understanding; how humans process “virtual” objects and the way associated tactile illusion is generated will be valuable for HCI (Human-Computer Interaction). Full article