The visual depth perception is composed of monocular and binocular depth cues. Studies show that in absence of binocular depth cues the performance of visuomotor tasks like pointing to or grasping objects is limited. Thus, binocular depth cues are of great importance for motor control required in everyday life. However, binocular depth cues like retinal disparity (basis for stereopsis) might be influenced due to developmental disorders of the visual system. For example, amblyopia in which one eye's visual input is not processed leads to loss of stereopsis. The primary amblyopia treatment is occlusion of the healthy eye to force the amblyopic eye to train. However, improvements in stereopsis are poor. Therefore, binocular treatments arose that equilibrate both eyes' visual input to enable binocular vision. However, most approaches rely on divided stimuli which do not account for loss of stereopsis. We created a Virtual Reality (VR) with reduced monocular depth cues in which a stereoscopic task is shown to both eyes simultaneously, consisting of two balls jumping towards the user. One ball appears closer to the user which must be identified. To evaluate the task performance the reaction time is measured. We validated our approach with 18 participants with stereopsis under three contrast settings including one leading to monocular vision. The number of correct responses reduces from 90% under binocular vision to 52% under monocular vision corresponding to random guessing. Our results indicate that it is possible to disable monocular depth cues and create a dynamic stereoscopic task inside a VR.

Gait supervision plays an important role in the diagnosis, analysis and rehabilitation of motor impairments and neurodegenerative disorders. For example, in Parkinson's disease, gait assessment is used for progression observation and medication guidance. Previous work has presented the potential of virtual reality (VR) supported gait applications. While virtual environments and user representation strategies are used for gait applications, the influence of appearance and context cues on gait performance is not extensively researched. In this paper, we analyzed the influence of avatar appearance, environment awareness, and camera perspective on gait parameters relevant for clinical application. Four different avatar appearances, varying in abstraction, two environmental settings, as well as an egocentric and exocentric camera perspective were compared in three walking tasks on a treadmill. Our results show that variability, as an indicator for gait stability, is significantly impacted by VR exposure in comparison to a real world (in vivo) baseline. Further, our results revealed that walking tasks influence gait behavior significantly different in VR compared to in vivo. Overall, these findings suggest that particular care has to be taken when assessing gait characteristics acquired from subjects immersed in VR and that equivalence of results with in vivo may not be blindly assumed.

The Stroop Test is a well known and regularly employed stressor in laboratory research. In contrast to other methods, it is not based on fear of physical harm or social shame. Consequently, it is more likely accepted by a wide population. In our always-on, technology-driven, social-media centered world, large-scale in-field stress research will need adequate experimental tools to explore the increasing prevalence of stress-related diseases without bringing subjects into laboratories. This is why we designed the Stroop Room: A virtual reality-based adaptation of the Stroop Test using elements of the virtual world to extend the demands of the original test and at the same time make it easily accessible. It is open source and can be used and improved by anyone as an in-the-wild, repeatable, laboratory-quality stressor. In this work, the method is presented and an evaluation study described, to demonstrate its effectiveness in provoking cognitive stress.

We explore motion parameters, more specifically gait parameters, as an objective indicator to assess simulator sickness in Virtual Reality (VR). We discuss the potential relationships between simulator sickness, immersion, and presence. We used two different camera pose (position and orientation) estimation methods for the evaluation of motion tasks in a large-scale VR environment: a simple model and an optimized model that allows for a more accurate and natural mapping of human senses. Participants performed multiple motion tasks (walking, balancing, running) in three conditions: a physical reality baseline condition, a VR condition with the simple model, and a VR condition with the optimized model. We compared these conditions with regard to the resulting sickness and gait, as well as the perceived presence in the VR conditions. The subjective measures confirmed that the optimized pose estimation model reduces simulator sickness and increases the perceived presence. The results further show that both models affect the gait parameters and simulator sickness, which is why we further investigated a classification approach that deals with non-linear correlation dependencies between gait parameters and simulator sickness. We argue that our approach could be used to assess and predict simulator sickness based on human gait parameters and we provide implications for future research.

Cognitive skills and their assessment gain increasing importance in soccer. In the past, athletes' perceptual-cognitive capabilities were only assessed using 2D media with its limitations. We used a virtual reality 360° video environment, where 15 high-skilled and 15 low-skilled soccer players (age 24 ± 3 years) experienced nine real-life soccer scenes from varying perspectives. The experience was frozen at crucial time points where they had to decide for one of three soccer actions. The recognition-action time and risk-level for decision were determined. Furthermore, six different interaction concepts were evaluated with respect to user experience, presence and immersion to find the most adequate and appealing one for assessment and training in soccer. Results show that high-skillers had a significantly lower overall recognition-action time. Risk-values for decisions did not differ significantly between skill levels.

Stress or anxiety disorders are a growing problem in industrialized countries. Those can be effectively countered by several relaxation techniques which are more effective using biofeedback. Modern virtual reality hardware provides a high level of immersion to its users. This directly affects the feeling of presence. An increased feeling of presence may allow biofeedback mechanisms to work more effectively. We build on this idea and explore how different visualizations of a user's cardiac activity in a virtual environment can be used in biofeedback scenarios - and how effective they are. Using a state-of-the-art virtual reality headset, 14 participants were subjected to four different visualizations of their own heart rate (one control visualization and three experimental visualizations). In different experiments, we examined whether they were able to estimate their heart rate based on the visualization and whether we could influence it subconsciously. Furthermore, we used the AttrakDiff questionnaire to assess the usability and attractiveness of each of the four visualizations. For the three non-reference ones, we observed significant positively correlating changes in the heart rate between the real-time true representation of the heart rate and a simulated increased heart rate visualization with a mean magnitude of 1.96 ± 0.39 beats per minute. The results from the source and number estimation experiments and the questionnaire led to the conclusion that the most appealing and best working visualization for biofeedback is a synchronized modulation/modification of the virtual environment itself.

Today, radiologists diagnose three dimensional medical data using two dimensional displays. When designing environments with optimal conditions for such a process various aspects like contrast, screen reflection and background light have to be considered. As shown in previous research, applying virtual environments in combination with a Head-Mounted Display for diagnostic imaging provides potential benefits to reduce issues of bad posture and diagnostic mistakes. However, there is little research in exploring the usability and user experience of such beneficial environments. In this work we designed and evaluated different means of interaction to increase radiologists' performance. Therefore we created a virtual reality radiology reading room and employed it to evaluate three different interaction techniques. These allow a direct, semi-direct and indirect manipulation for performing scrolling- and windowing- tasks which are the most important for a radiologist. A study including nine radiologists was conducted and evaluated using the User Experience Questionnaire. Results indicate that direct manipulation is the preferred interaction technique, it outscored the other two control possibilities in attractiveness and pragmatic quality.

Eye tracking offers many opportunities for direct device control in smart environments, but issues such as the need for calibration and the Midas touch problem make it impractical. In this paper, we propose AmbiGaze, a smart environment that employs the animation of targets to provide users with direct control of devices by gaze only through smooth pursuit tracking. We propose a design space of means of exposing functionality through movement and illustrate the concept through four prototypes. We evaluated the system in a user study and found that AmbiGaze enables robust gaze-only interaction with many devices, from multiple positions in the environment, in a spontaneous and comfortable manner.