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Current neuroscientific models of bodily self-consciousness (BSC) argue that inaccurate integration of sensory signals leads to altered states of BSC. Indeed, using virtual reality technology, observers viewing a fake or virtual body while being exposed to tactile stimulation of the real body, can experience illusory ownership over-and mislocalization towards-the virtual body (Full-Body Illusion, FBI). Among the sensory inputs contributing to BSC, the vestibular system is believed to play a central role due to its importance in estimating self-motion and orientation. This theory is supported by clinical evidence that vestibular loss patients are more prone to altered BSC states, and by recent experimental evidence that visuo-vestibular conflicts can disrupt BSC in healthy individuals. Nevertheless, the contribution of vestibular information and self-motion perception to BSC remains largely unexplored. Here, we investigate the relationship between alterations of BSC and self-motion sensitivity in healthy individuals. Fifteen participants were exposed to visuo-vibrotactile conflicts designed to induce an FBI, and subsequently to visual rotations that evoked illusory self-motion (vection). We found that synchronous visuo-vibrotactile stimulation successfully induced the FBI, and further observed a relationship between the strength of the FBI and the time necessary for complete vection to arise. Specifically, higher self-reported FBI scores across synchronous and asynchronous conditions were associated to shorter vection latencies. Our findings are in agreement with clinical observations that vestibular loss patients have higher FBI susceptibility and lower vection latencies, and argue for increased visual over vestibular dependency during altered states of BSC., Competing Interests: The authors have declared that no competing interests exist.

Previous behavioral and neurophysiological research has shown better memory for horizontal than for vertical locations. In these studies, participants navigated toward these locations. In the present study we investigated whether the orientation of the spatial plane per se was responsible for this difference. We thus had participants learn locations visually from a single perspective and retrieve them from multiple viewpoints. In three experiments, participants studied colored tags on a horizontally or vertically oriented board within a virtual room and recalled these locations with different layout orientations (Exp. 1) or from different room-based perspectives (Exps. 2 and 3). All experiments revealed evidence for equal recall performance in horizontal and vertical memory. In addition, the patterns for recall from different test orientations were rather similar. Consequently, our results suggest that memory is qualitatively similar for both vertical and horizontal two-dimensional locations, given that these locations are learned from a single viewpoint. Thus, prior differences in spatial memory may have originated from the structure of the space or the fact that participants navigated through it. Additionally, the strong performance advantages for perspective shifts (Exps. 2 and 3) relative to layout rotations (Exp. 1) suggest that configurational judgments are not only based on memory of the relations between target objects, but also encompass the relations between target objects and the surrounding room-for example, in the form of a memorized view. [ABSTRACT FROM AUTHOR]

In driving simulation, simulator tilt is used to reproduce sustained linear acceleration. In order to feel realistic, this tilt is performed at a rate below the human tilt rate detection threshold, which is usually assumed constant. However, it is known that many factors affect the threshold, such as visual information, simulator motion in additional directions, or the driver’s active effort required for controlling the vehicle. Here we investigated the effect of these factors on the roll rate detection threshold during simulated curve driving. Ten participants reported whether they detected roll motion in multiple trials during simulated curve driving, while roll rate was varied over trials. Roll rate detection thresholds were measured under four conditions. In the first three conditions, participants were moved passively through a curve with the following: (i) roll only in darkness; (ii) combined roll/sway in darkness; (iii) combined roll/sway and visual information. In the fourth (iv) condition participants actively drove through the curve. The results showed that roll rate thresholds in simulated curve driving increase, that is, sensitivity decreases, when the roll tilt is combined with sway motion. Moreover, an active control task seemed to further increase the detection threshold, that is, impair motion sensitivity, but with large individual differences. We hypothesize that this is related to the level of immersion during the task. [ABSTRACT FROM AUTHOR]

Establishing verbal memory traces for non-verbal stimuli was reported to facilitate or inhibit memory for the non-verbal stimuli. We show that these effects are also observed in a domain not indicated before--wayfinding. Fifty-three participants followed a guided route in a virtual environment. They were asked to remember half of the intersections by relying on the visual impression only. At the other 50% of the intersections, participants additionally heard a place name, which they were asked to memorize. For testing, participants were teleported to the intersections and were asked to indicate the subsequent direction of the learned route. In Experiment 1, intersections' names were arbitrary (i.e., not related to the visual impression). Here, participants performed more accurately at unnamed intersections. In Experiment 2, intersections' names were descriptive and participants' route memory was more accurate at named intersections. Results have implications for naming places in a city and for wayfinding aids. [ABSTRACT FROM AUTHOR]

In human perception, the ability to determine eye height is essential, because eye height is used to scale heights of objects, velocities, affordances and distances, all of which allow for successful environmental interaction. It is well understood that eye height is fundamental to determine many of these percepts. Yet, how eye height itself is provided is still largely unknown. While the information potentially specifying eye height in the real world is naturally coincident in an environment with a regular ground surface, these sources of information can be easily divergent in similar and common virtual reality scenarios. Thus, we conducted virtual reality experiments where we manipulated the virtual eye height in a distance perception task to investigate how eye height might be determined in such a scenario. We found that humans rely more on their postural cues for determining their eye height if there is a conflict between visual and postural information and little opportunity for perceptual-motor calibration is provided. This is demonstrated by the predictable variations in their distance estimates. Our results suggest that the eye height in such circumstances is informed by postural cues when estimating egocentric distances in virtual reality and consequently, does not depend on an internalized value for eye height. [ABSTRACT FROM AUTHOR]

Considerable empirical evidence has shown influences of the action capabilities of the body on the perception of sizes and distances. Generally, as one׳s action capabilities increase, the perception of the relevant distance (over which the action is to be performed) decreases and vice versa. As a consequence, it has been proposed that the body׳s action capabilities act as a perceptual ruler, which is used to measure perceived sizes and distances. In this set of studies, we investigated this hypothesis by assessing the influence of arm׳s reach on the perception of distance. By providing participant with a self-representing avatar seen in a first-person perspective in virtual reality, we were able to introduce novel and completely unfamiliar alterations in the virtual arm׳s reach to evaluate their impact on perceived distance. Using both action-based and visual matching measures, we found that virtual arm׳s reach influenced perceived distance in virtual environments. Due to the participants׳ inexperience with the reach alterations, we also were able to assess the amount of experience with the new arm׳s reach required to influence perceived distance. We found that minimal experience reaching with the virtual arm can influence perceived distance. However, some reaching experience is required. Merely having a long or short virtual arm, even one that is synchronized to one׳s movements, is not enough to influence distance perception if one has no experience reaching. [ABSTRACT FROM AUTHOR]

Our bodies are the most intimately familiar objects we encounter in our perceptual environment. Virtual reality provides a unique method to allow us to experience having a very different body from our own, thereby providing a valuable method to explore the plasticity of body representation. In this paper, we show that women can experience ownership over a whole virtual body that is considerably smaller or larger than their physical body. In order to gain a better understanding of the mechanisms underlying body ownership, we use an embodiment questionnaire, and introduce two new behavioral response measures: an affordance estimation task (indirect measure of body size) and a body size estimation task (direct measure of body size). Interestingly, after viewing the virtual body from first person perspective, both the affordance and the body size estimation tasks indicate a change in the perception of the size of the participant's experienced body. The change is biased by the size of the virtual body (overweight or underweight). Another novel aspect of our study is that we distinguish between the physical, experienced and virtual bodies, by asking participants to provide affordance and body size estimations for each of the three bodies separately. This methodological point is important for virtual reality experiments investigating body ownership of a virtual body, because it offers a better understanding of which cues (e.g. visual, proprioceptive, memory, or a combination thereof) influence body perception, and whether the impact of these cues can vary between different setups. [ABSTRACT FROM AUTHOR]

In this paper we address the problem of controlling the motion of a group of unmanned aerial vehicles (UAVs) bound to keep a formation defined in terms of only relative angles (i.e. a bearing formation). This problem can naturally arise within the context of several multi-robot applications such as, e.g. exploration, coverage, and surveillance. First, we introduce and thoroughly analyze the concept and properties of bearing formations, and provide a class of minimally linear sets of bearings sufficient to uniquely define such formations. We then propose a bearing-only formation controller requiring only bearing measurements, converging almost globally, and maintaining bounded inter-agent distances despite the lack of direct metric information.The controller still leaves the possibility of imposing group motions tangent to the current bearing formation. These can be either autonomously chosen by the robots because of any additional task (e.g. exploration), or exploited by an assisting human co-operator. For this latter ‘human-in-the-loop’ case, we propose a multi-master/multi-slave bilateral shared control system providing the co-operator with some suitable force cues informative of the UAV performance. The proposed theoretical framework is extensively validated by means of simulations and experiments with quadrotor UAVs equipped with onboard cameras. Practical limitations, e.g. limited field-of-view, are also considered. [ABSTRACT FROM PUBLISHER]

Background: When we talk to one another face-to-face, body gestures accompany our speech. Motion tracking technology enables us to include body gestures in avatar-mediated communication, by mapping one's movements onto one's own 3D avatar in real time, so the avatar is self-animated. We conducted two experiments to investigate (a) whether head-mounted display virtual reality is useful for researching the influence of body gestures in communication; and (b) whether body gestures are used to help in communicating the meaning of a word. Participants worked in pairs and played a communication game, where one person had to describe the meanings of words to the other. Principal Findings: In experiment 1, participants used significantly more hand gestures and successfully described significantly more words when nonverbal communication was available to both participants (i.e. both describing and guessing avatars were self-animated, compared with both avatars in a static neutral pose). Participants 'passed' (gave up describing) significantly more words when they were talking to a static avatar (no nonverbal feedback available). In experiment 2, participants' performance was significantly worse when they were talking to an avatar with a prerecorded listening animation, compared with an avatar animated by their partners' real movements. In both experiments participants used significantly more hand gestures when they played the game in the real world. Conclusions: Taken together, the studies show how (a) virtual reality can be used to systematically study the influence of body gestures; (b) it is important that nonverbal communication is bidirectional (real nonverbal feedback in addition to nonverbal communication from the describing participant); and (c) there are differences in the amount of body gestures that participants use with and without the head-mounted display, and we discuss possible explanations for this and ideas for future investigation. [ABSTRACT FROM AUTHOR]

This study investigated the effect of body-based information (proprioception, etc.) when participants navigated large-scale virtual marketplaces that were either small (Experiment 1) or large in extent (Experiment 2). Extent refers to the size of an environment, whereas scale refers to whether people have to travel through an environment to see the detail necessary for navigation. Each participant was provided with full body-based information (walking through the virtual marketplaces in a large tracking hall or on an omnidirectional treadmill), just the translational component of body-based information (walking on a linear treadmill, but turning with a joystick), just the rotational component (physically turning but using a joystick to translate) or no body-based information (joysticks to translate and rotate). In large and small environments translational body-based information significantly improved the accuracy of participants' cognitive maps, measured using estimates of direction and relative straight line distance but, on its own, rotational body-based information had no effect. In environments of small extent, full body-based information also improved participants' navigational performance. The experiments show that locomotion devices such as linear treadmills would bring substantial benefits to virtual environment applications where large spaces are navigated, and theories of human navigation need to reconsider the contribution made by body-based information, and distinguish between environmental scale and extent. [ABSTRACT FROM AUTHOR]

Our ability to return to the start of a route recently performed in darkness is thought to reflect path integration of motion-related in- formation. Here we provide evidence that motion-related interocep- tive representations (proprioceptive, vestibular, and motor efference copy) combine with visual representations to form a single multi- modal representation guiding navigation. We used immersive virtual reality to decouple visual inputfrom motion-related interoception by manipulating the rotation ortranslation gain of the visual projection. First, participants walked an outbound path with both visual and interoceptive input, and returned to the start in darkness, demon- strating the influences of both visual and interoceptive information in a virtual reality environment. Next, participants adapted to visual rotation gains in the virtual environment, and then performed the path integration task entirely in darkness. Our findings were accu- rately predicted bya quantitative model in which visual and intero- ceptive inputs combine into a single multimodal representation guiding navigation, and are incompatible with a model of separate visual and interoceptive influences on action (in which path integra- tion in darkness must rely solely on interoceptive representations). Overall, our findings suggest that a combined multimodal represen- tation guides large-scale navigation, consistent with a role for visual imagery or a cognitive map. [ABSTRACT FROM AUTHOR]

Few HMD-based virtual environment systems display a rendering of the user's own body. Subjectively, this often leads to a sense of disembodiment in the virtual world. We explore the effect of being able to see one's own body in such systems on an objective measure of the accuracy of one form of space perception. Using an action-based response measure, we found that participants who explored near space while seeing a fully-articulated and tracked visual representation of themselves subsequently made more accurate judgments of absolute egocentric distance to locations ranging from 4 m to 6 m away from where they were standing than did participants who saw no avatar. A nonanimated avatar also improved distance judgments, but by a lesser amount. Participants who viewed either animated or static avatars positioned 3 m in front of their own position made subsequent distance judgments with similar accuracy to the participants who viewed the equivalent animated or static avatar positioned at their own location. We discuss the implications of these results on theories of embodied perception in virtual environments. [ABSTRACT FROM AUTHOR]

Mental rotation is the capacity to predict the orientation of an object or the layout of a scene after a change in viewpoint. Previous studies have shown that the cognitive cost of mental rotations is reduced when the viewpoint change results from the observer's motion rather than the object or spatial layout's rotation. The classical interpretation for these findings involves the use of automatic updating mechanisms triggered during self-motion. Nevertheless, little is known about how this process is triggered and particularly how sensory cues combine in order to facilitate mental rotations. The previously existing setups, either real or virtual, did not allow disentangling the different sensory contributions, which motivated the development of a new high-end virtual reality platform overcoming these technical limitations. In the present paper we will start by a didactic review of the literature on mental rotations and expose the current technical limitations. Then we will fully describe the experimental platform that was developed at the Max Planck Institute for Biological Cybernetics in Tübingen. The setup consisted of a cabin mounted on the top of a six degree-of-freedom Stewart platform inside of which was an adjustable seat, a physical table with a screen embedded, and a large projection screen. A 5-PC cluster running Virtools was used to drive the platform and render the two passive stereovision scenes that were displayed on the table and background screens. Finally, we will present the experiment using this setup that allowed replicating the classical advantage found for a moving observer, which validates our setup. We will conclude by discussing the experimental validation and the advantages of such a setup. [ABSTRACT FROM AUTHOR]

This study examines the working memory systems involved in human wayfinding. In the learning phase, 24 participants learned two routes in a novel photorealistic virtual environment displayed on a 220° screen while they were disrupted by a visual, a spatial, a verbal, or—in a control group—no secondary task. In the following wayfinding phase, the participants had to find and to “virtually walk” the two routes again. During this wayfinding phase, a number of dependent measures were recorded. This research shows that encoding wayfinding knowledge interfered with the verbal and with the spatial secondary task. These interferences were even stronger than the interference of wayfinding knowledge with the visual secondary task. These findings are consistent with a dual-coding approach of wayfinding knowledge. [ABSTRACT FROM AUTHOR]

An overall assessment of phobic fear requires not only a verbal self-report of fear but also an assessment of behavioral and physiological responses. Virtual reality can be used to simulate realistic (phobic) situations and therefore should be useful for inducing emotions in a controlled, standardized way. Verbal and physiological fear reactions were examined in 15 highly tunnel-fearful and 15 matched control participants in 3 virtual driving scenarios: an open environment, a partially open tunnel (gallery), and a closed tunnel. Highly tunnel-fearful participants were characterized by elevated fear responses specifically during tunnel drives as reflected in verbal fear ratings, heart rate reactions, and startle responses. Heart rate and fear ratings differentiated highly tunnel-fearful from control participants with an accuracy of 88% and 93%, respectively. Results indicate that virtual environments are valuable tools for the assessment of fear reactions and should be used in future experimental research. [ABSTRACT FROM AUTHOR]

The literature often suggests that proprioceptive and especially vestibular cues are required for navigation and spatial orientation tasks involving rotations of the observer. To test this notion, we conducted a set of experiments in virtual environments in which only visual cues were provided. Participants had to execute turns, reproduce distances, or perform triangle completion tasks. Most experiments were performed in a simulated 3D field of blobs, thus restricting navigation strategies to path integration based on optic flow. For our experimental set-up (half-cylindrical 180 deg. projection screen), optic flow information alone proved to be sufficient for untrained participants to perform turns and reproduce distances with negligible systematic errors, irrespective of movement velocity. Path integration by optic flow was sufficient for homing by triangle completion, but homing distances were biased towards the mean response. Additional landmarks that were only temporarily available did not improve homing performance. However, navigation by stable, reliable landmarks led to almost perfect homing performance. Mental spatial ability test scores correlated positively with homing performance, especially for the more complex triangle completion tasks—suggesting that mental spatial abilities might be a determining factor for navigation performance. In summary, visual path integration without any vestibular or kinesthetic cues can be sufficient for elementary navigation tasks like rotations, translations, and triangle completion. [ABSTRACT FROM AUTHOR]

The notion of body-based scaling suggests that our body and its action capabilities are used to scale the spatial layout of the environment. Here we present four studies supporting this perspective by showing that the hand acts as a metric which individuals use to scale the apparent sizes of objects in the environment. However to test this, one must be able to manipulate the size and/or dimensions of the perceiver’s hand which is difficult in the real world due to impliability of hand dimensions. To overcome this limitation, we used virtual reality to manipulate dimensions of participants’ fully-tracked, virtual hands to investigate its influence on the perceived size and shape of virtual objects. In a series of experiments, using several measures, we show that individuals’ estimations of the sizes of virtual objects differ depending on the size of their virtual hand in the direction consistent with the body-based scaling hypothesis. Additionally, we found that these effects were specific to participants’ virtual hands rather than another avatar’s hands or a salient familiar-sized object. While these studies provide support for a body-based approach to the scaling of the spatial layout, they also demonstrate the influence of virtual bodies on perception of virtual environments. [ABSTRACT FROM AUTHOR]

We examined how a highly familiar environmental space—one’s city of residence—is represented in memory. Twenty-six participants faced a photo-realistic virtual model of their hometown and completed a task in which they pointed to familiar target locations from various orientations. Each participant’s performance was most accurate when he or she was facing north, and errors increased as participants’ deviation from a north-facing orientation increased. Pointing errors and latencies were not related to the distance between participants’ initial locations and the target locations. Our results are inconsistent with accounts of orientation-free memory and with theories assuming that the storage of spatial knowledge depends on local reference frames. Although participants recognized familiar local views in their initial locations, their strategy for pointing relied on a single, north-oriented reference frame that was likely acquired from maps rather than experience from daily exploration. Even though participants had spent significantly more time navigating the city than looking at maps, their pointing behavior seemed to rely on a north-oriented mental map. [ABSTRACT FROM PUBLISHER]

This paper addresses the interactions between human wayfinding performance, the mental representation of routes, and the geometrical layout of path intersections. The conclusions of this paper are based on the results of a virtual reality empirical experiment. The study consisted of a route-learning and reproduction task and two choice reaction tasks measuring the acquired knowledge of route decision points. In order to relate the recorded behaviour to the geometry of the environment, a specific adaptation of an isovist-based spatial analysis that accounts for directional bias in human spatial perception and representation was developed. The analyses applied provided conclusive evidence of correspondences between the geometrical properties of environments as captured by isovists and their mental representations. [ABSTRACT FROM AUTHOR]

Abstract: In the presented exploratory study, quantitative relations between the experience of architectural spaces and physical properties were investigated using virtual reality (VR) simulations. Geometric properties from a component-based description of rectangular rooms were tested on their suitability as predictor variables for experiential qualities. In a virtual-reality-based perceptual experiment, qualities of 16 vacant rectangular interiors were rated in eight principal categories by 16 participants using the semantic differential scaling technique. The simulated scenes were automatically generated by means of a custom made utility that also provided for the component-based room descriptions. The data analysis revealed strong correlations between several scene features and the averaged rated experience. For example, a preference for ratios near to the golden section could be observed for spatial proportions, which are not directly perceivable. Altogether, a set of five widely independent factors (openness, two room proportions, room area, and balustrade height) turned out to be most effective for describing the observed variance in the attributed experiential qualities. The combination of realistic virtual reality simulations and psychophysical data raising methods proved to be an effective means for basic architectural research. Several quantitative relations between physical properties and the emotional experience of architectural space could be demonstrated. [Copyright &y& Elsevier]

Abstract: Many scientists have demonstrated that compared to the real world egocentric distances in head-mounted display virtual environments are underestimated. However, distance perception in large screen immersive displays has received less attention. We investigate egocentric distance perception in a virtual office room projected using a semi-spherical, a Max Planck Institute CyberMotion Simulator cabin and a flat large screen immersive display. The goal of our research is to systematically investigate distance perception in large screen immersive displays with commonly used technical specifications. We specifically investigate the role of distance to the target, stereoscopic projection and motion parallax on distance perception. We use verbal reports and blind walking as response measures for the real world experiment. Due to the limited space in the three large screen immersive displays we use only verbal reports as the response measure for the experiments in the virtual environment. Our results show an overall underestimation of distance perception in the large screen immersive displays, while verbal estimates of distances are nearly veridical in the real world. We find that even when providing motion parallax and stereoscopic depth cues to the observer in the flat large screen immersive display, participants estimate the distances to be smaller than intended. Although stereo cues in the flat large screen immersive display do increase distance estimates for the nearest distance, the impact of the stereoscopic depth cues is not enough to result in veridical distance perception. Further, we demonstrate that the distance to the target significantly influences the percent error of verbal estimates in both the real and virtual world. The impact of the distance to the target on the distance judgments is the same in the real world and in two of the used large screen displays, namely, the MPI CyberMotion Simulator cabin and the flat displays. However, in the semi-spherical display we observe a significantly different influence of distance to the target on verbal estimates of egocentric distances. Finally, we discuss potential reasons for our results. Based on the findings from our research we give general suggestions that could serve as methods for improving the LSIDs in terms of the accuracy of depth perception and suggest methods to compensate for the underestimation of verbal distance estimates in large screen immersive displays. [Copyright &y& Elsevier]

Abstract: Vection is defined as the compelling sensation of illusory self-motion elicited by a moving sensory, usually visual, stimulus. This paper presents collected introspective data, user discomfort and perceived speed data for the experience of linear, circular, and curvilinear vection in a large-screen, immersive, virtual environment. As a first step we evaluated the effectiveness of a floor projection on the perception of vection for four trajectories: linear forward, linear backward, circular left, and circular right. The floor projection, which considerably extended the field of view, was found to significantly improve the introspective measures of linear, but not circular, vection experienced in a photo-realistic three-dimensional town. In a second study we investigated the differences between 12 different motion trajectories on the illusion of self-motion. In this study we found that linear translations to the left and right are perceived as the least convincing, while linear down is perceived as the most convincing of the linear trajectories. Second, we found that while linear forward vection is not perceived to be very convincing, curvilinear forward vection is reported to be as convincing as circular vection. In a third and final experiment we investigated the perceived speed for all different trajectories and acquired data based on simulator sickness questionnaires to compute a discomfort factor associated with each type of trajectory. Considering our experimental results, we offer suggestions for increasing the sense of self-motion in simulators and VE applications, specifically to increase the number of curvilinear trajectories (as opposed to linear ones) and, if possible, add floor projection in order to improve the illusory sense of self-motion. [Copyright &y& Elsevier]