Target detection performance in helmet-mounted and conventional dome displays

An experiment was conducted to assess visual target detection performance using a helmet-mounted display (HMD) and a conventional flight simulation dome display. Measures of workload and mood were also obtained. Participants in both viewing conditions scanned an area 120 degrees vertical by 240 degrees horizontal while attempting to locate targets that appeared to be approaching them from one of a possible 18 locations. Results indicated significantly superior performance in the conventional dome display. Workload and mood measures also showed a significant advantage for the dome display. Results are discussed in terms of their implications for the design and use of HMD systems as components of airborne virtual environment interfaces.     

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.     

Virtual reality in the rehabilitation of the upper limb after stroke: the user's perspective.

Our group has developed a relatively low-cost virtual reality (VR) system for rehabilitation of the upper limb following stroke. Our system is immersive in that the participant views a representation of their arm and hand, reaching and retrieving objects in the virtual environment (VE), through a head-mounted display (HMD). This is thought to increase the participant's sense of presence in the VE and may lead to improved rehabilitation outcomes. However, use of immersion, particularly with our low-cost system, may increase the incidence of side effects reported. Therefore, the aim of this project was to assess the interaction of healthy users and those following stroke, in terms of their experience of presence in the VE and the rate of self-reported side effects. Differences in rates of perceived exertion, levels of enjoyment, and sense of control between both groups were also explored.     

Virtual/real transfer of spatial knowledge: benefit from visual fidelity provided in a virtual environment and impact of active navigation

The purpose of this study was to evaluate the effect the visual fidelity of a virtual environment (VE) (undetailed vs. detailed) has on the transfer of spatial knowledge based on the navigation mode (passive vs. active) for three different spatial recall tasks (wayfinding, sketch mapping, and picture sorting). Sixty-four subjects (32 men and 32 women) participated in the experiment. Spatial learning was evaluated by these three tasks in the context of the Bordeaux district. In the wayfinding task, the results indicated that the detailed VE helped subjects to transfer their spatial knowledge from the VE to the real world, irrespective of the navigation mode. In the sketch-mapping task, the detailed VE increased performances compared to the undetailed VE condition, and allowed subjects to benefit from the active navigation. In the sorting task, performances were better in the detailed VE; however, in the undetailed version of the VE, active learning either did not help the subjects or it even deteriorated their performances. These results are discussed in terms of appropriate perceptive-motor and/or spatial representations for each spatial recall task.     

Is the street-crossing behavior with a head-mounted display different from that behavior in a CAVE? A study among young adults and children

The use of virtual reality (VR) has become increasingly popular in the field of traffic psychology, where realistic traffic situations can be simulated and pedestrians‘ actual crossing behavior can be studied. There are two main kinds of pedestrian simulators: one uses a technology based on rear-projection screens (Cave Automatic Virtual Environment, or CAVE); the other uses a head-mounted display (HMD). Despite their extensive use, it is yet to determine whether they are equally suitable for studying street crossing. The present study was aimed at comparing street-crossing behavior and subjective evaluations in an HMD-based (HTC vive pro) pedestrian simulator and a CAVE-like pedestrian simulator, among young adults and 12-year-old children. Thirty young adults and twenty-six children performed 36 street-crossing trials (combining different speeds, traffic conditions, and gap sizes) on each of the two simulators. The results indicated that, compared to the CAVE-condition participants, HMD-condition participants accepted more crossing trials (hence, shorter gaps), initiated their crossings sooner, crossed at a slower speed, had shorter safety margins, and caused more collisions. The main difference between the two devices was in crossing initiation, which occurred markedly earlier (1.72 s) with the HMD than in the CAVE: the perception–action coupling was less finely tuned in the CAVE, probably because visual information in front of the pedestrian was missing due the absence of ground projection and 3D rendering. A significant effect of vehicle-approach speed was observed for both devices, with more unsafe behaviors at 60 km/h than at 40 km/h. Children displayed riskier crossing behavior than young adults did, with more accepted crossings, slower crossing speeds, shorter safety margins, and higher collision rates, especially in the HMD. Compared to the CAVE, the HMD received higher ratings for level of presence and a preference for VR, but also higher simulator-sickness scores. No adverse effects of exposure to virtual reality was found on stereoacuity or postural balance. The suitability of using CAVE and HMD simulators is discussed, especially for studying child pedestrians.     

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.     

Visual ergonomics of head-mounted displays

Head-mounted displays (HMDs) are increasingly used in the field and in the laboratory. Prolonged use of HMDs requires their ergonomics to be optimized in order to reduce discomfort. Among factors causing visual load are the physical/optical properties of eyepieces used in HMDs. Many HMD eyepieces are adjusted manually to fit the individual requirements of the user. Proper adjustment of the eyepieces requires some knowledge of visual ergonomics. Additionally, in order to enable comfortable viewing, restrictions on the visual information presented in HMDs, such as the motion of objects in virtual depth, must be considered. Visual performance and therefore visual load depends on the display technology used in HMDs.     

Visual short-term memory benefit for objects on different 3-D surfaces

Visual short-term memory (VSTM) plays an important role in visual cognition. Although objects are located on different 3-dimensional (3-D) surfaces in the real world, how VSTM capacity may be influenced by the presence of multiple 3-D surfaces has never been examined. By manipulating binocular disparities of visual displays, the authors found that more colored objects could be held in VSTM when they were placed on 2 rather than on 1 planar 3-D surfaces. This between-surface benefit in VSTM was present only when binding of objects' colors to their 3-D locations was required (i.e., when observers needed to remember which color appeared where). When binding was not required, no between-surface benefit in VSTM was observed. This benefit in VSTM could not be attributed to the number of spatial locations attended within a given surface. It was not due to a general perceptual grouping effect either, because grouping by motion and grouping by different regions of the same surface did not yield the same benefit. This increment in capacity indicates that VSTM benefits from the placement of objects in a 3-D scene.     

The effect of landmark and body-based sensory information on route knowledge

Two experiments investigated the effects of landmarks and body-based information on route knowledge. Participants made four out-and-back journeys along a route, guided only on the first outward trip and with feedback every time an error was made. Experiment 1 used 3-D virtual environments (VEs) with a desktop monitor display, and participants were provided with no supplementary landmarks, only global landmarks, only local landmarks, or both global and local landmarks. Local landmarks significantly reduced the number of errors that participants made, but global landmarks did not. Experiment 2 used a head-mounted display; here, participants who physically walked through the VE (translational and rotational body-based information) made 36% fewer errors than did participants who traveled by physically turning but changing position using a joystick. Overall, the experiments showed that participants were less sure of where to turn than which way, and journey direction interacted with sensory information to affect the number and types of errors participants made.     

Treatment of acrophobia in virtual reality: the role of immersion and presence

In this study the effects of virtual reality exposure therapy (VRET) were investigated in patients with acrophobia. Feelings of presence in VRET were systematically varied by using either a head-mounted display (HMD) (low presence) or a computer automatic virtual environment (CAVE) (high presence). VRET in general was found to be more effective than no treatment. No differences were found in effectiveness between VRET using an HMD or CAVE. Results were maintained at 6 months follow-up. Results of VRET were comparable with those of exposure in vivo (Cyberpsychology and Behavior 4 (2001) 335). In treatment completers no relationship was found between presence and anxiety. Early drop-outs experienced less acrophobic complaints and psychopathology in general at pre-test. They also experienced less presence and anxiety in the virtual environment used in session one as compared to patients that completed VRET.     

Spatial updating during locomotion does not eliminate viewpoint-dependent visual object processing

Two experiments were conducted to investigate whether locomotion to a novel test view would eliminate viewpoint costs in visual object processing. Participants performed a sequential matching task for object identity or object handedness, using novel 3-D objects displayed in a head-mounted display. To change the test view of the object, the orientation of the object in 3-D space and the test position of the observer were manipulated independently. Participants were more accurate when the test view was the same as the learned view than when the views were different no matter whether the view change of the object was 50° or 90°. With 50° rotations, participants were more accurate at novel test views caused by participants’ locomotion (object stationary) than caused by object rotation (observer stationary) but this difference disappeared when the view change was 90°. These results indicate that facilitation of spatial updating during locomotion occurs within a limited range of viewpoints, but that such facilitation does not eliminate viewpoint costs in visual object processing.     

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.     

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.     

Segregation by color and stereoscopic depth in three-dimensional visual space

Two experiments were conducted to investigate how color and stereoscopic depth information are used to segregate objects for visual search in three-dimensional (3-D) visual space. Eight observers were asked to indicate the alphanumeric category (letter or digit) of the target which had its unique color and unique depth plane. In Experiment 1, distractors sharing a common depth plane or a common color appeared in spatial contiguity in thexy plane. The results suggest that visual search for the target involves examination of kernels formed by homogeneous items sharing the same color and depth. In Experiment 2, thexy contiguity of distractors sharing a common color or a common depth plane was varied. The results showed that when target-distractor distinction becomes more difficult on one dimension, the other dimension becomes more important in performing visual search, as indicated by a larger effect on search time. This suggests that observers can make optimal use of the information available. Finally, color had a larger effect on search time than did stereoscopic depth. Overall, the results support models of visual processing which maintain that perceptual segregation and selective attention are determined by similarity among objects in 3-D visual space on both spatial and nonspatial stimulus dimensions.     

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.     

Spatial context learning in visual search and change detection

Humans conduct visual search more efficiently when the same display is presented for a second time, showing learning of repeated spatial contexts. In this study, we investigate spatial context learning in two tasks: visual search and change detection. In both tasks, we ask whether subjects learn to associate the target with the entire spatial layout of a repeated display (configural learning) or with individual distractor locations (nonconfigural learning). We show that nonconfigural learning results from visual search tasks, but not from change detection tasks. Furthermore, a spatial layout acquired in visual search tasks does not enhance change detection on the same display, whereas a spatial layout acquired in change detection tasks moderately enhances visual search. We suggest that although spatial context learning occurs in multiple tasks, the content of learning is, in part, task specific.     

Spatial knowledge of a real school environment acquired from virtual or physical models by able-bodied children and children with physical disabilities

In Experiment 1, 2 groups of able-bodied children were exposed to both a complex single-tier virtual environment (VE) and a physical model of a different environment. For 1 group, the VE accurately modeled a real school, and for the other group the physical model did so. In transfer testing in the real school, orientation accuracy was greater in the group exposed to the VE of the real school. In Experiment 2, children with physical disabilities explored the VE model of the real school and were tested as in the 1st experiment. Measures of orientation accuracy and map-placing were significantly better in this group than in the guessing adult control group. The results illustrate the potential for VEs as useful spatial training media.     

Internally augmented displays: contingent aftereffects as performance aids

Previous research on visual contingent aftereffects has been concerned with examining the effects of various parameters (e.g., spatial frequency and luminance) on the adaptation to, and decay of, contingent aftereffects. The current study tested the viability of using visual contingent aftereffects in a display context. Using established characteristics of contingent aftereffects, a program of contingent aftereffect adaptation was designed. Studies were conducted to determine if subjects who were adapted to see visual contingent aftereffects invoked by a visual display could achieve more rapid or certain identification of a display under low luminance conditions. The results confirmed (a) that contingent aftereffects can improve performance on a visual discrimination task requiring information from a display and (b) that contingent aftereffects are more enhanced at low levels of illumination.     

Three-dimensional audio versus head-down traffic alert and collision avoidance system displays

The advantage of a head-up auditory display for situational awareness was evaluated in an experiment designed to measure and compare the acquisition time for capturing visual targets under two conditions: standard head-down Traffic Alert and Collision Avoidance System display and three-dimensional (3-D) audio Traffic Alert and Collision Avoidance System presentation. (The technology used for 3-D audio presentation allows a stereo headphone user to potentially localize a sound at any externalized position in 3-D auditory space). Ten commercial airline crews were tested under full-mission simulation conditions at the NASA-Ames Crew-Vehicle Systems Research Facility Advanced Concepts Flight Simulator. Scenario software generated targets corresponding to aircraft that activated a 3-D aural advisory (the head-up auditory condition) or a standard, visual-audio TCAS advisory (map display with monaural audio alert). Results showed a significant difference in target acquisition time between the two conditions, favoring the 3-D audio Traffic Alert and Collision Avoidance System condition by 500 ms.     

Internal representation of visual texture as the basis for the judgment of similarity

The relationship between Fourier spectra of visual textures (represented both by the actual frequency components and by the response of four hypothetical channels selectively sensitive to spatial frequency) and the perceptual appearance of the textures was investigated. Thirty textures were synthesized by combining seven spatial frequencies whose amplitudes were randomly chosen and then scaled to give an overall contrast of .9. Similarity judgments were collected using both the method of triadic comparison (two subjects, 4,060 trials each) and the method of paired comparison (six subjects, 435 trials each). The similarity judgments were subjected to MDSCAL and INDSCAL dimensions were found to be optimally oriented in terms of spatial frequency information without rotation. The seven spatial frequency components accounted for 90.6% of the variance in the 3-D INDSCAL space, while the four channels accounted for 91.8% of the variance in the first two dimensions. The data further suggest that the four channels may interact in an opponent process manner. The results support the idea that the visual internal representation of stimuli is based on spatial frequency analysis rather than feature extraction.