Field dependency and the sense of object-presence in haptic virtual environments.

Virtual environment (VE) users often report having a sense of being present in the virtual place or a sense that the virtual object is present in their environment. This sense of presence depends on both the technological fidelity (e.g., in graphics, haptics) and the users' cognitive/ personality characteristics. This study examined the correlation between user's cognitive style on the field-dependency dimension and the level of object-presence they reported in a haptic VE. Results indicated that field-independent individuals reported higher presence ratings compared to field-dependent participants. We hypothesize that field-independents' advantage in reorganizing the perceptual field and constructing it according to their previously acquired internal knowledge enables them to cognitively reconstruct the VE experience more efficiently by selectively attending only to the relevant cues and by filling in the gap of missing information with their previous knowledge and creative imagination. This active and creative cognitive process may be behind the enhanced sense of presence. In addition, we raise a possible linkage between field dependency, the sense of presence, and simulator sickness phenomenon.     

Factors that influence presence in educational virtual environments.

The present article is a part of a project for the measurement of presence in educational virtual environments (VEs), since presence is correlated with higher levels of cognitive performance and emotional development, factors that contribute to knowledge construction. The aim of our study was to investigate the sense of presence of 12-year-old pupils within an educational VE representing an ancient Greek house through a sense of embodiment and the ability to handle task performance, while using various peripheral devices. This is the first report on presence measurement with children, based on the indication that children and adults may apply very unrelated criteria. Our results showed statistically significant differences on the level of tiredness and ease of use in using six different input devices. The combination of the keyboard and mouse and the keyboard on its own were the least tedious and easiest input devices, giving a sense of presence as stated by the pupils. Environmental richness and the high level of interactivity within the VE resulted in a high degree of presence for almost all the pupils. The majority of them felt a sense of presence whilst driving the avatar, indicating that presence is significantly correlated with pupils' degree of association with their virtual bodies. All the pupils felt a sense of presence when wearing the head-mounted display. Our findings are in line with those of other researchers and show evidence of personal, social and environmental presence.     

A treadmill and motion coupled virtual reality system for gait training post-stroke.

A virtual reality (VR)-based locomotor training system has been developed for gait rehabilitation post-stroke. The system consists of a self-paced treadmill mounted onto a 6-degrees-of-freedom motion platform. Virtual environments (VEs) that are synchronized with the speed of the treadmill and the motions of the platform are rear-projected onto a screen in front of the walking subject. A feasibility study was conducted to test the capability of two stroke patients and one healthy control to be trained with the system. Three VE scenarios (corridor walking, street crossing, and park stroll) were woven into a gait-training program that provided three levels of complexity (walking speed, slopes, collision avoidances), progression criteria (number of successful trials) and knowledge of results. Results show that, with practice, patients can effectively increase their gait speed as demanded by the task and adapt their gait with respect to the change in physical terrain. However, successful completion of tasks requiring adaptation to increasing demands related to speed and physical terrains does not necessarily predict the patient's ability to anticipate and avoid collision with obstacles during walking. This feasibility study demonstrates that persons with stroke are able to adapt to this novel VR system and be immersed in the VEs for gait training.     

Comparison of grasping movements made by healthy subjects in a 3-dimensional immersive virtual versus physical environment

Virtual reality (VR) technology is being used with increasing frequency as a training medium for motor rehabilitation. However, before addressing training effectiveness in virtual environments (VEs), it is necessary to identify if movements made in such environments are kinematically similar to those made in physical environments (PEs) and the effect of provision of haptic feedback on these movement patterns. These questions are important since reach-to-grasp movements may be inaccurate when visual or haptic feedback is altered or absent. Our goal was to compare kinematics of reaching and grasping movements to three objects performed in an immersive three-dimensional (3D) VE with haptic feedback (cyberglove/grasp system) viewed through a head-mounted display to those made in an equivalent physical environment (PE). We also compared movements in PE made with and without wearing the cyberglove/grasp haptic feedback system. Ten healthy subjects (8 women, 62.1 ± 8.8 years) reached and grasped objects requiring 3 different grasp types (can, diameter 65.6 mm, cylindrical grasp; screwdriver, diameter 31.6 mm, power grasp; pen, diameter 7.5 mm, precision grasp) in PE and visually similar virtual objects in VE. Temporal and spatial arm and trunk kinematics were analyzed. Movements were slower and grip apertures were wider when wearing the glove in both the PE and the VE compared to movements made in the PE without the glove. When wearing the glove, subjects used similar reaching trajectories in both environments, preserved the coordination between reaching and grasping and scaled grip aperture to object size for the larger object (cylindrical grasp). However, in VE compared to PE, movements were slower and had longer deceleration times, elbow extension was greater when reaching to the smallest object and apertures were wider for the power and precision grip tasks. Overall, the differences in spatial and temporal kinematics of movements between environments were greater than those due only to wearing the cyberglove/grasp system. Differences in movement kinematics due to the viewing environment were likely due to a lack of prior experience with the virtual environment, an uncertainty of object location and the restricted field-of-view when wearing the head-mounted display. The results can be used to inform the design and disposition of objects within 3D VEs for the study of the control of prehension and for upper limb rehabilitation.     

Use of Virtual Environments for the Acquisition of Spatial Knowledge: Comparison Among Different Visual Displays

This experiment investigated the effects of three visual display systems differing in immersiveness: A wide field of view (FOV) 3-D helmet-mounted display (HMD); a 3-D HMD with a narrow FOV; and a stationary, rear-projection, wide screen display (WSD). Soldiers explored a virtual environment (VE) representing an actual, unfamiliar heliport. Measures of spatial knowledge of the heliport and presence were recorded. Pretest-posttest differences showed that exploration of the VE transferred to the actual heliport. Visual display had no effect on spatial knowledge of the heliport or on presence. Measures of susceptibility to presence correlated with reported presence only in the WSD condition. Results question popular notions about VEs, which assume that visual-spatial learning is more effective the more immersive the visual display.     

An experimental study on fear of public speaking using a virtual environment.

This paper examines a necessary condition for successful exploitation of a virtual environment (VE) in therapeutic intervention for fear of public speaking. The condition is that clients experience a degree of anxiety in the VE that is similar to what they would have been expected to experience in a similar real world setting. We refer to this as a "presence" response. The experimental study involved 20 people who were confident public speakers and 16 who were phobic, assessed on a standard psychological scale. Half of each group spoke within a VE depicting an empty seminar room, and the other half within the same room but populated by a neutrally behaving virtual audience of five people. Three responses were measured--a questionnaire-based measure of anxiety, a measure of self-focused attention on somatic responses, and actual heart rate. On all responses, the people with phobia showed a significant increase in signs of anxiety when speaking to the virtual audience compared to the empty room, whereas the confident people did not. The result was strong in spite of the relatively low representational and behavioral fidelity of the virtual characters.     

Cross-association analysis of EEG and EMG signals according to movement intention state

Rehabilitation within three months plays a significant role in the recovery of damaged motor functions following the onset of a stroke. To increase the effectiveness of rehabilitation, it is important to perform rehabilitative exercises with movement intention. This study analyzed the association between electroencephalogram (EEG) and electromyogram (EMG) signals in healthy individuals in an attempt to verify the differences between the two signals in corticomuscular connectivity as well as the time delay in the flow of information in accordance with the presence of movement intention. To examine the relationship between the brain and muscles, coherence and mutual information analyses were performed on the EEG signals in the motor cortex and EMG signals in the flexor digitorum superficialis muscle during grasping training. Coherence and mutual information between EEG and EMG signals were significantly higher and the time delay of information flow was shorter when subjects performed active exercise with movement intention than when they performed passive exercise without movement intention. These findings could be applied to the rehabilitation of stroke patients to develop a rehabilitative training system with heightened effectiveness through verification of the presence of movement intention in the patients.     

Does Narrative Feedback Enhance Children's Motor Learning in a Virtual Environment?

Augmented feedback has motivational and informational functions in motor learning, and is a key feature of practice in a virtual environment (VE). This study evaluated the impact of narrative (story-based) feedback as compared to standard feedback during practice of a novel task in a VE on typically developing children's motor learning, motivation and engagement. Thirty-eight children practiced navigating through a virtual path, receiving narrative or non-narrative feedback following each trial. All participants improved their performance on retention but not transfer, with no significant differences between groups. Self-reported engagement was associated with acquisition, retention and transfer for both groups. A narrative approach to feedback delivery did not offer an additive benefit; additional affective advantages of augmented feedback for motor learning in VEs should be explored.     

The Use of the Term Virtual Reality in Post-Stroke Rehabilitation: A Scoping Review and Commentary

Virtual reality (VR) offers many opportunities for post-stroke rehabilitation. However, “VR” can refer to several types of computer-based rehabilitation systems. Since these systems may impact the feasibility and the efficacy of VR interventions, consistent terminology is important. In this study, we aimed to optimize the terminology for VR-based post-stroke rehabilitation by assessing whether and how review papers on this topic defined VR and what types of mixed reality systems were discussed. In addition, this review can inspire the use of consistent terminology for other researchers working with VR. We assessed the use of the term VR in review papers on post-stroke rehabilitation extracted from Scopus, Web of Science and PubMed. We also developed a taxonomy distinguishing 16 mixed reality systems based on three factors: immersive versus semi-immersive displays, the way in which real and virtual information is mixed, and the main input device. 64% of the included review papers (N = 121) explicitly defined VR and 33% of them described different subtypes of VR, with immersive and non-immersive VR as the most common distinction. The most frequently discussed input devices were motion-capture cameras and handheld devices, while regular 2D monitors were the most frequently mentioned output devices. Our analysis revealed that reviews on post-stroke VR rehabilitation did not or only broadly defined “VR” and did not focus on a specific system. Since the efficacy and feasibility of rehabilitation may depend on the specific system, we propose a new data-driven taxonomy to distinguish different systems, which is expected to facilitate communication amongst researchers and clinicians working with virtual reality.     

Using a virtual reality system to study balance and walking in a virtual outdoor environment: a pilot study.

Falls and fall-related injuries are a major problem for elderly persons. Most falls occur during walking and turning, and the risk of falling increases when attention is diverted to something besides walking. It is often difficult to standardize methods for testing balance and fall tendency in a clinically relevant setting. We describe the development of a system using a virtual environment (VE) to assess how attention demanding and unexpected events influence a person's capacity to control balance and movement. The hardware in the system consists of a head-mounted display (HMD), a magnetic tracker system, and two SGI computers. The software consists of the image generation of the VE and the management and visualization of motion tracking data. In a preliminary pilot study eight subjects (age 23-80) participated. Each subject walked on a normal floor and was visually presented a familiar outdoor environment in the HMD. They were exposed to different unexpected events, such as a virtual snowfall and tilting of the VE. Disturbances of balance and walking patterns such as changes in speed, stride length and balance reactions like slipping were observed. Two subjects experienced symptoms of cyber sickness with a SSQ score above 25 points. Walking with sensors only did not affect walking time, but in VE the subjects generally walked more slowly. Virtual tilting of the environment had an impact on balance performance during walking. This effect was not observed while the test subjects were walking in a virtual snowfall. The model needs further development but may hold a potential for clinical use.     

Active versus passive learning and testing in a complex outside built environment

A review of the evidence on active and passive learning in virtual environments (VEs) suggests that both conditions have shown superiority under some conditions of learning and testing, but there is no consistent outcome pattern. Measures of transfer between virtual and real environments have also revealed a variety of outcomes. Following either active or passive learning in a VE, experiment 1 assessed measures of orientation and distance estimation in that VE and in a real-world equivalent environment. On measures of direct and relative distance, more accurate estimates were found for active than passive VE explorers. A suggestion was also noted for the orientation estimates to benefit from real-world rather than VE testing. With an improvement to the procedure, experiment 2 found similar real versus virtual orientation judgements, suggesting that an opportunity for active learning during the test procedure probably influenced orientation measures in experiment 1. We conclude that the effects of interactivity are unreliable and vary with the measures used, and that testing in virtual and real environments leads to similar outcomes.     

虚拟环境中临境感及其测量方法

虚拟环境（VE）中的临境感是用户感知身处VE而产生的一种主观体验,是评价VE的重要指标。VE临境感产生的基础在于个体VE某一特征的集中注意,其程度强弱在一定范围内取决于个体分配于VE的注意资源量,受诸如计算机技术设备等系统因素、表现为个体差异的用户因素以及人机对话过程中交互因素的影响。在此基础上本文从生理指标（生理测量法、心率变化和皮肤电阻变化）、行为指标（姿势变化和冲突条件下的刺激定位）、心理物理学（对比法和跨通道匹配法）、主观评价（WS-PQ、SUS-PQ、ITC-SOPI和直接主观评价法）和绩效衡量对VE临境感的测量方法进行总结和简单评价。     

Transformation of flow in rehabilitation: The role of advanced communication technologies

Authentic rehabilitation requires the active participation of patients and their involvement with opportunities for action and development. Within this framework, in this article we outline the possibility of using two emerging computing and communication technologies—ambient intelligence (AmI) and virtual reality (VR)—for a new breed of rehabilitative and clinical applications based on a strategy defined astransformation of flow. Transformation of flow is a person’s ability to exploit an optimal (flow) experience to identify and use new and unexpected psychological resources as sources of involvement. We identify the feeling ofpresence—the feeling of being in a world that exists outside oneself—as the theoretical link between the technology and rehabilitation. AmI and VR are used to trigger broad empowerment processes induced by a strong sense of presence, leading to greater agency and control over one’s actions and environment.     

The Rutgers Arm, a rehabilitation system in virtual reality: a pilot study.

Stroke is one of the leading causes of death and disability worldwide. Its prevalence calls for innovative rehabilitation methods. The Rutgers Arm is a novel upper extremity rehabilitation system consisting of a low-friction table, three-dimensional (3D) tracker, custom forearm support, PC workstation, library of Java 3D virtual reality (VR) exercises, clinical database module, and a tele-rehabilitation extension. The system was tested on a chronic stroke subject, under local and tele-rehabilitation conditions, over 5 weeks of training. Results show improvements in arm motor control and shoulder range of motion, corresponding to improved Fugl-Meyer test scores. Exercise duration, level of difficulty, and patient motivation were maintained under tele-rehabilitaion. A 1-week retention trial showed that gains were maintained.     

Dynamic action in virtual environments: constraints on the accessibility of action knowledge in children and adults

In a series of three experiments, we probed the accessibility of action knowledge in different versions of a virtual environment (VE) with 7-year-old children and adults. Using a PHANToM haptic interface, participants performed a virtual throwing task in which they tried to propel a ball from a table to hit a target on the ground. In Experiments 1 and 2, the virtual scene was presented on a computer monitor, and, in Experiment 3, it was projected by using a video projector so that the vertical and horizontal dimensions and the spatial location of the VE corresponded to the real-world dimensions. Results indicate that action knowledge is accessible even in a nonimmersive VE, but also suggest that the need to recalibrate perceptual-motor mappings constrains the accessibility of this kind of intuitive knowledge.     

Individual differences in spatial learning from computer-simulated environments

A multivariate study examined relationships between the following factors: paper-and-pencil assessments of verbal and spatial ability, ability to form an accurate spatial representation of a large real-world environment, gender, computer attitudes and experience, proficiency with the navigational interface of a virtual environment (VE), and the ability to acquire and transfer spatial knowledge from a VE. Psychometrically assessed spatial ability and proficiency with the navigational interface were found to make substantial contributions to individual differences in the ability to acquire spatial information from a VE. Gender influenced many VE-related tasks, primarily through its relationship with interface proficiency and spatial ability. Measures of spatial knowledge of a VE maze were highly predictive of subsequent performance in a similar real-world maze, suggesting that VEs can be useful for training people about real-world spaces.     

Correcting distance estimates by interacting with immersive virtual environments: effects of task and available sensory information

The tendency to underestimate egocentric distances in immersive virtual environments (VEs) is not well understood. However, previous research (A. R. Richardson & D. Waller, 2007) has demonstrated that a brief period of interaction with the VE prior to making distance judgments can effectively eliminate subsequent underestimation. Here the authors examine the mechanism underlying the effect of VE interaction and the conditions that may give rise to it. In Experiment 1, after interacting with an immersive VE, participants tended to overestimate distances in the physical world, indicating that the interaction involved a recalibration of the perceptual-motor system. Experiment 2 demonstrates that visual information is not necessary (and that body-based information is necessary) during the interaction period for it to have a positive effect on subsequent distance estimation accuracy. Experiment 3 illustrates that the interaction task does not need to be goal directed in order to be effective.     

Dynamic action in virtual environments: Constraints on the accessibility of action knowledge in children and adults

In a series of three experiments, we probed the accessibility of action knowledge in different versions of a virtual environment (VE) with 7-year-old children and adults. Using a PHANToM^TM haptic interface, participants performed a virtual throwing task in which they tried to propel a ball from a table to hit a target on the ground. In Experiments 1 and 2, the virtual scene was presented on a computer monitor, and, in Experiment 3, it was projected by using a video projector so that the vertical and horizontal dimensions and the spatial location of the VE corresponded to the real-world dimensions. Results indicate that action knowledge is accessible even in a nonimmersive VE, but also suggest that the need to recalibrate perceptual-motor mappings constrains the accessibility of this kind of intuitive knowledge.     

First‐perspective alignment effects in a computer‐simulated environment

In Experiment 1, participants explored two desktop, virtual environments (VEs), each comprising three city streets connected at right angles; for each participant one VE was open and one was enclosed. Following the first VE exploration, orientation estimates to remembered test locations were most accurate when participants imagined themselves aligned, rather than 90° misaligned or 180° or contra‐aligned, with the first part of the route. In the second VE, the effect was attenuated and the data pattern conformed to that anticipated from an orientation‐free memory. Experiment 2 followed the procedure of Experiment 1, but omitted the alignment tests after the first VE; following the second VE exploration, orientation estimates presented a similar pattern to those in first test of Experiment 1. These data are discussed in terms of cognitive load.