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The presented master thesis deals with the perception of the speed vehicle crew (not the drivers) in traffic in terms of different aspects, that influencing the feeling while driving in the vehicle. This is primarily about the approximation of factors that may have an impact on the speed. The aim of the thesis is to propose an appropriate methodology of measurement and subsequent evaluation of acquired date, which leads to an improvement in the idea of whether witnesses of traffic accidents are indicative of the speed of the vehicles, at reasonable real speed.

This master’s thesis deals with the issue of the perception of speed of a vehicle from pedestrian’s point of view. The theoretical part consists of a research into sense perception of humans and construction of motor vehicles. The practical part designs and describes the experiment which was performed in order to provide data used for analyzing different factors and their effect on the accuracy of vehicle speed estimations.

Among the biggest challenges in the development of VR has been creating an overall sense of immersion and presence as well as finding methods to reduce cybersickness. These aspects have been major obstacles to the widespread adoption of virtual reality since its existence. Research has shown that various camera techniques have been investigated to reduce cybersickness and enhance the immersive experience in VR. Hence, camera settings are an important tool when it comes to reducing cybersickness as well as creating a sense of immersion in VR. This study aims to determine what effect that lock onboard camera to horizon setting can have on players of VR racing games in terms of the player's sense of immersion and potential for cybersickness. It relies on an experiment with the lock onboard camera setting enabled and disabled utilizing the VR racing game Assetto Corsa. The data collection involved a mix methodology of questionnaires as well as interviews and included a Motion Sickness Susceptibility Questionnaire (MSSQ) and Cybersickness VR Questionnaire (CSQ-VR). The research results do not provide the definitive information on which camera was better to use. However, the difference was relatively minimal, even though the locked camera had demonstrated better results in terms of cybersickness intensity. All of the results suggest that immersion is highly subjective and a matter of personal preference, as indicated by all of the findings.

No / In this report, we evaluate the role of visual areas responsive to motion in the human brain in the perception of stimulus speed. We first identified and localized V1, V3A, and V5/MT+ in individual participants on the basis of blood oxygenation level-dependent responses obtained in retinotopic mapping experiments and responses to moving gratings. Repetitive transcranial magnetic stimulation (rTMS) was then used to disrupt the normal functioning of the previously localized visual areas in each participant. During the rTMS application, participants were required to perform delayed discrimination of the speed of drifting or spatial frequency of static gratings. The application of rTMS to areas V5/MT and V3A induced a subjective slowing of visual stimuli and ( often) caused increases in speed discrimination thresholds. Deficits in spatial frequency discrimination were not observed for applications of rTMS to V3A or V5/MT+. The induced deficits in speed perception were also specific to the cortical site of TMS delivery. The application of TMS to regions of the cortex adjacent to V5/MT and V3A, as well as to area V1, produced no deficits in speed perception. These results suggest that, in addition to area V5/MT+, V3A plays an important role in a cortical network that underpins the perception of stimulus speed in the human brain. / BBSRC

Dans ce travail de thèse, nous avons tout d’abord étudié comment l’information de mouvement est intégrée pour estimer la vitesse d’une texture aléatoire afin de la suivre réflexivement avec les yeux ou d’estimer perception son déplacement. Dans une seconde série d’études, nous avons étudié comment la distribution spatiale du contraste dans une texture affecte à la fois les mouvements oculaires de fixation et la reconnaissance perceptive. A ces fins, nous avons utilisé un nouvel ensemble de stimuli visuels, des textures pseudo-naturelles dans lesquelles on peut finement contrôler la statistique (moyenne, variance) des fréquences spatiales et/ou temporelles. La première partie explore l’intégration et le décodage de information fréquentielle spatio-temporelle visuelle pour les réponses de poursuite réflexes et la discrimination perceptive. Nous montrons que l’action tire complètement partie de la richesse du stimuli en intégrant sur toute la distribution pour estimer la vitesse : accélération initiale, précision et robustesse sont améliorées. Au contraire, la performance perceptive décroit pour des stimuli à bandes passantes larges. Cette dissociation se maintient sur une large place d’intégration temporelle. La seconde partie élargie cette approche à la distribution spatiale de l’information et à ces différentes échelles. Nous montrons que le comportement oculaire de fixation dépend de la composition fréquentielle d’une texture, en termes de moyenne et de fréquence. Saccade et micro-saccades se distribuent au cours de la fixation de façon coordonnée en fonction de cette statistique. In fine, cette dernière joue sur la carte de salience calculée à partir de l’image. / We focused on the impact of the statistical distributions of visual information on these various behavioral responses. We asked first how motion information is integrated to estimate speed in order to perform either a speed discrimination task or to control reflexive tracking eye movements. Next, we investigated how spatial distribution in textures affects both pattern recognition and fixational eye movements. To do so, we used a set of artificial stimuli that are naturalistic textures where we can maintain a tight control on their information contents as for instance their spatio-temporal frequency bandwidth. The first studies compared speed information decoding for ocular following eye movements and perceptual speed discrimination. We found a strong dissociation where ocular following take full advantage by the enlargement of the spatio-temporal frequency bandwidth while perceptual speed discrimination is largely impaired for large bandwidth stimuli. Such dissociation remains over a large temporal integration window. We propose an adaptive gain control mechanism to explain this opposite dependencies. The second series of experimental studies investigate the properties of fixation eye movements (microsaccade and saccade) as a function of the mean and variance of the spatial frequency content of visual static textures. We show that several characteristics of fixational saccades (location, direction and amplitude) varied systematically with the distribution of spatial frequencies. The spatial distribution of the fixation zones could be best predicted from the saliency maps of the stimuli.