Human Visual Navigation: Effects of Visual Context, Navigation Mode, and Gender

Abstract This thesis extends research on human visual path integration using optic flow cues. In three experiments, a large-scale path-completion task was contextualised within highly-textured authentic virtual environments. Real-world navigational experience was further simulated, through the inclusion of a large roundabout on the route. Three semi-surrounding screens provided a wide field of view. Participants were able to perform the task, but directional estimates showed characteristic errors, which can be explained with a model of distance misperception on the outbound roads of the route. Display and route layout parameters had very strong effects on performance. Gender and navigation mode were also influential. Participants consistently underestimated the final turn angle when simulated self-motion was viewed passively, on large projection screens in a driving simulator. Error increased with increasing size of the internal angle, on route layouts based on equilateral or isosceles triangles. A compressed range of responses was found. Higher overall accuracy was observed when a display with smaller desktop computer monitors was used; especially when simulated self-motion was actively controlled with a steering wheel and foot pedals, rather than viewed passively. Patterns and levels of error depended on route layout, which included triangles with non-equivalent lengths of the two outbound roads. A powerful effect on performance was exerted by the length of the "approach segment" on the route: that is, the distance travelled on the first outbound road, combined with the distance travelled between the two outbound roads on the roundabout curve. The final turn angle was generally overestimated on routes with a long approach segment (those with a long first road and a 60° or 90° internal angle), and underestimated on routes with a short approach segment (those with a short first road or the 120° internal angle). Accuracy was higher for active participants on routes with longer approach segments and on 90° angle trials, and for passive participants on routes with shorter approach segments and on 120° angle trials. Active participants treated all internal angles as 90° angles. Participants performed with lower overall accuracy when optic flow information was disrupted, through the intermittent presentation of self-motion on the small-screen display, in a sequence of static snapshots of the route. Performance was particularly impaired on routes with a long approach segment, but quite accurate on those with a short approach segment. Consistent overestimation of the final angle was observed, and error decreased with increasing size of the internal angle. Participants treated all internal angles as 120° angles. The level of available visual information did not greatly affect estimates, in general. The degree of curvature on the roundabout mainly influenced estimates by female participants in the Passive condition. Compared with males, females performed less accurately in the driving simulator, and with reduced optic flow cues; but more accurately with the small-screen display on layouts with a short approach segment, and when they had active control of the self-motion. The virtual environments evoked a sense of presence, but this had no effect on task performance, in general. The environments could be used for training navigational skills where high precision is not required

Expectations and Beliefs in Immersive Virtual Reality Environments: Managing of Body Perception

Real and Perceived Feet Orientation Under Fatiguing and Non-Fatiguing Conditions in an Immersive Virtual Reality Environment ABSTRACT Lower limbs position sense is a complex yet poorly understood mechanism, influenced by many factors. Hence, we investigated the position sense of lower limbs through feet orientation with the use of Immersive Virtual Reality (IVR). Participants had to indicate how they perceived the real 1050 orientation of their feet by orientating a virtual representation of the feet that was shown in an IVR 1051 scenario. We calculated the angle between the two virtual feet (α-VR) after a high-knee step-in-1052 place task. Simultaneously, we recorded the real angle between the two feet (α-R) (T1). Hence, we 1053 assessed if the acute fatigue impacted the position sense. The same procedure was repeated after 1054 inducing muscle fatigue (T2) and after 10 minutes from T2 (T3). Finally, we also recorded the time 1055 needed to confirm the perceived position before and after the acute fatigue protocol. Thirty healthy 1056 adults (27.5 ± 3.8: 57% female, 43% male) were immersed in an IVR scenario with a representation 1057 of two feet. We found a mean difference between α-VR and α-R of 20.89° [95% CI: 14.67°, 27.10°] 1058 in T1, 16.76° [9.57°, 23.94°] in T2, and 16.34° [10.00°, 22.68°] in T3. Participants spent 12.59, 17.50 1059 and 17.95 seconds confirming the perceived position of their feet at T1, T2, T3, respectively. 1060 Participants indicated their feet as forwarding parallel though divergent, showing a mismatch in the 1061 perceived position of feet. Fatigue seemed not to have an impact on position sense but delayed the 1062 time to accomplish this task.The Effect of Context on Eye-Height Estimation in Immersive Virtual Reality: a Cross-Sectional Study ABSTRACT Eye-height spatial perception provides a reference to scale the surrounding environment. It is the result of the integration of visual and postural information. When these stimuli are discordant, the perceived spatial parameters are distorted. Previous studies in immersive virtual reality (IVR) showed that spatial perception is influenced by the visual context of the environment. Hence, this study explored how manipulating the context in IVR affects individuals’ eye-height estimation. Two groups of twenty participants each were immersed in two different IVR environments, represented by a closed room (Wall - W) and an open field (No Wall - NW). Under these two different conditions, participants had to adjust their virtual perspective, estimating their eye height. We calculated the perceived visual offset as the difference between virtual and real eye height, to assess whether the scenarios and the presence of virtual shoes (Feet, No Feet) influenced participants’ estimates at three initial offsets (+100 cm, +0 cm, -100 cm). We found a mean difference between the visual 1679 offsets registered in those trials that started with 100 cm and 0 cm offsets (17.24 cm [8.78; 25.69]) 1680 and between 100 cm and -100 cm offsets (22.35 cm [15.65; 29.05]). Furthermore, a noticeable mean difference was found between the visual offsets recorded in group W, depending on the presence or absence of the virtual shoes (Feet VS No Feet: -6.12 [-10.29, -1.95]). These findings describe that different contexts influenced eye-height perception.Positive Expectations led to Motor Improvement: an Immersive Virtual Reality Pilot Study ABSTRACT This pilot study tested the feasibility of an experimental protocol that evaluated the effect of different positive expectations (verbal and visual-haptic) on anterior trunk flexion. Thirty-six participants were assigned to 3 groups (G0, G+ and G++) that received a sham manoeuvre while immersed in Immersive Virtual Reality (IVR). In G0, the manouvre was paired with by neutral verbal statement. In G+ and G++ the manouvre was paired with a positive verbal statement, but only G++ received a visual-haptic illusion. The illusion consisted of lifting a movable tile placed in front of the participants, using its height to raise the floor level in virtual reality. In this way, participants experienced the perception of touching the floor, through the tactile and the virtual visual afference. The distance between fingertips and the floor was measured before, immediately after, and after 5 minutes from the different manouvres. A major difference in anterior trunk flexion was found for G++ compared to the other groups, although it was only significant compared to G0. This result highlighted the feasibility of the present study for future research on people with mobility limitations (e.g., low back pain or kinesiophobia) and the potential role of a visual-haptic illusion in modifying the performance of trunk flexion

Touch-sensitive : cybernetic images and replicant bodies in the post-industrial age

This thesis uses Deleuzian cybernetics to advance upon post-modern accounts of the contemporary image economy. It begins with the hypothesis that the schizophrenic behaviours of late capitalism have induced an irreparable crisis in the inherited `specular economy' (Irigaray). This is manifested as the breakdown of the laws of generalised equivalence between truth, value and meaning and the end of a stable signifier-signified relationship - theorised as the escape of reality into 'hyperreality', or the world become simulation according to Baudrillard. It will expose the insufficiency of post-modern accounts which theorise this crisis in representation via methods which fail to escape their own always already representational terms and it will then rigorously follow through the implications of an image economy which is constituted by simulations which are `genuinely' sourceless, which do not imitate a prior reality but which rather synthesise forces and relations. To escape the closed loop of representationalism, it will divert attention away from the signifier and will concentrate on the sub-representational power of images to re-engineer reality and to re-invent the limits of the body. Using the theory and practice of Deleuze, Spinoza, Bergson, Benjamin and Virilio, it will treat images as planes of corporeal becoming - as material entities, virtual avatars, possessional states and conductors of pre-personal affect. Post-modem accounts which cite the overwhelming predominance of images sit uncomfortably with the theories of French anti-ocularcentrism - accessed here via Irigaray and Lyotard - which mark the demise of vision and its attached representational order. This paradox requires that a new perceptual relation be mapped - figured here as entirely corporeal, as tactile and synesthetic (Mcluhan) and therefore immersive. Both 'affect' and 'intensity', as modes of pre-personal perception, will be treated as tactile interactions for these responses to images demand that a body be always 'in touch' with its environment, always anorganically altering its perceptual capacities by rules of feedback. It will be argued that in this reality studio, the body no longer perceives via a specular light source, solid form and assumed phallocentric meaning. The proposed synthesis between cybernetic imaging technologies, immanent perceptual criteria and the ever-changing state of the body requires an engagement with the female since she bears a privileged relation to this scenario. In the specular economy, women have been assumed, like faithful images, to secondarily reproduce an underlying, phallocentric truth. However, it will be shown that just as images can work nonrepresentationally, so too can female bodies; on the one hand appearing representational but on the other conducting radically subversive effects. Where bodies and images are such simulatory becomings it will be shown how the female is neither representationally ordered (social constructivism) nor essentially defined (biological reductivism) but is rather cybernetically engineered. Throughout, her privileged access to the virtual realm beyond language will be used to substantiate the major claim of this thesis that cybernetic simulation is more concerned with the material alteration of an environment rather than with the implementation of linguistic obligation

Robotics 2010

Without a doubt, robotics has made an incredible progress over the last decades. The vision of developing, designing and creating technical systems that help humans to achieve hard and complex tasks, has intelligently led to an incredible variety of solutions. There are barely technical fields that could exhibit more interdisciplinary interconnections like robotics. This fact is generated by highly complex challenges imposed by robotic systems, especially the requirement on intelligent and autonomous operation. This book tries to give an insight into the evolutionary process that takes place in robotics. It provides articles covering a wide range of this exciting area. The progress of technical challenges and concepts may illuminate the relationship between developments that seem to be completely different at first sight. The robotics remains an exciting scientific and engineering field. The community looks optimistically ahead and also looks forward for the future challenges and new development