The role of multisensory feedback in the objective and subjective evaluations of fidelity in virtual reality environments.

The use of virtual reality in academic and industrial research has been rapidly expanding in recent years therefore evaluations of the quality and effectiveness of virtual environments are required. The assessment process is usually done through user evaluation that is being measured whilst the user engages with the system. The limitations of this method in terms of its variability and user bias of pre and post-experience have been recognised in the research literature. Therefore, there is a need to design more objective measures of system effectiveness that could complement subjective measures and provide a conceptual framework for the fidelity assessment in VR. There are many technological and perceptual factors that can influence the overall experience in virtual environments. The focus of this thesis was to investigate how multisensory feedback, provided during VR exposure, can modulate a user’s qualitative and quantitative experience in the virtual environment. In a series of experimental studies, the role of visual, audio, haptic and motion cues on objective and subjective evaluations of fidelity in VR was investigated. In all studies, objective measures of performance were collected and compared to the subjective measures of user perception. The results showed that the explicit evaluation of environmental and perceptual factors available within VR environments modulated user experience. In particular, the results shown that a user’s postural responses can be used as a basis for the objective measure of fidelity. Additionally, the role of augmented sensory cues was investigated during a manual assembly task. By recording and analysing the objective and subjective measures it was shown that augmented multisensory feedback modulated the user’s acceptability of the virtual environment in a positive manner and increased overall task performance. Furthermore, the presence of augmented cues mitigated the negative effects of inaccurate motion tracking and simulation sickness. In the follow up study, the beneficial effects of virtual training with augmented sensory cues were observed in the transfer of learning when the same task was performed in a real environment. Similarly, when the effects of 6 degrees of freedom motion cuing on user experience were investigated in a high fidelity flight simulator, the consistent findings between objective and subjective data were recorded. By measuring the pilot’s accuracy to follow the desired path during a slalom manoeuvre while perceived task demand was increased, it was shown that motion cuing is related to effective task performance and modulates the levels of workload, sickness and presence. The overall findings revealed that multisensory feedback plays an important role in the overall perception and fidelity evaluations of VR systems and as such user experience needs to be included when investigating the effectiveness of sensory feedback signals. Throughout this thesis it was consistently shown that subjective measures of user perception in VR are directly comparable to the objective measures of performance and therefore both should be used in order to obtain a robust results when investigating the effectiveness of VR systems. This conceptual framework can provide an effective method to study human perception, which can in turn provide a deeper understanding of the environmental and cognitive factors that can influence the overall user experience, in terms of fidelity requirements, in virtual reality environments

Complexité des situations, expérience, tension et vigilance : quels impacts sur la charge de travail et les performances de jeunes conducteurs ?

The aim of this thesis is to identify the links between factors contributing to accidents among young drivers, by analyzing the effects of situation complexity and driving experience on workload, tension, vigilance and performance. The general hypothesis is that costly situations, i.e. simple and very complex, and the lack of experience can lead to high energy expenditure. A high level of tension and a low level of vigilance can thus result in performance impairments through the increase of workload, characterizing a driver's overload. This should be observed earlier for novices who had a Traditionally-Trained Learning (TTL), then for those who had an Early-Trained Learning (ETL), then for drivers arriving at the end of the probationary period, and finally for more experienced drivers. A first experiment carried out on subjective data has confirmed the links between the levels of workload, tension and vigilance depending on the situation complexity. However, only novices ETL were overloaded with the situation complexity, due to ineffective strategies. A second experiment carried out on subjective and physiological data has also confirmed the links between the levels of workload, tension and vigilance, with an underestimation of the physiological level by the novices TTL. The two compared groups (novices TTL and drivers at the end of the probation) were overloaded in complex situation, either because they didn't adopt the appropriate strategies (novices TTL), either by lack of flexibility in relation to the automatisms (drivers at the end of the probation). The results establishing the links between the characteristics of the driving situation and the individual characteristics leading to road accidents will allow adapting awareness actions and modules of driving training.L'objectif de cette thèse est d'identifier les liens entre les facteurs accidentogènes chez les jeunes conducteurs, en analysant les effets de la complexité de la situation et de l'expérience de conduite sur la charge de travail, la tension, la vigilance et les performances. L'hypothèse générale est que les situations coûteuses, i.e. simples et très complexes, ainsi que le manque d'expérience peuvent mener à une forte dépense énergétique. Ainsi, un haut niveau de tension et un faible niveau de vigilance peuvent provoquer des dégradations de performances à travers la hausse de la charge de travail, caractérisant une surcharge du conducteur. Ceci devrait s'observer plus précocement pour les novices ayant suivi un Apprentissage Traditionnel (AT), puis pour ceux ayant suivi un Apprentissage Anticipé de la Conduite (AAC), puis pour les conducteurs arrivant à la fin du permis probatoire, et enfin pour les plus expérimentés. Une première expérimentation menée sur des données subjectives a confirmé les liens entre les niveaux de charge de travail, de tension et de vigilance en fonction de la complexité de la situation. Cependant, seuls les novices AAC étaient surchargés avec la complexité de la situation, de part des stratégies inefficaces. Une seconde expérimentation menée sur des données subjectives et physiologiques a également confirmé les liens entre les niveaux de charge de travail, de tension et de vigilance, avec une sous-estimation du niveau physiologique par les novices AT. Les deux groupes comparés (novices AT et conducteurs à la fin du permis probatoire) étaient surchargés en situation complexe, soit car ils n'adoptaient pas les stratégies adéquates (novice), soit par manque de flexibilité par rapport aux automatismes (conducteurs à la fin du permis probatoire). Les résultats établissant les liens entre des caractéristiques de la situation de conduite et des caractéristiques individuelles menant à des accidents de la route pourront permettre d'adapter les actions de sensibilisation et les modules de formations à la conduite