We examined relations between eye movements (single-fixation durations) and RSVP-based event-related potentials (ERPs; N400’s) recorded during reading the same sentences in two independent experiments. Longer fixation durations correlated with larger N400 amplitudes. Word frequency and predictability of the fixated word as well as the predictability of the upcoming word accounted for this covariance in a path-analytic model. Moreover, larger N400 amplitudes entailed longer fixation durations on the next word, a relation accounted for by word frequency. This pattern offers a neurophysiological correlate for the lag-word frequency effect on fixation durations: Word processing is reliably expressed not only in fixation durations on currently fixated words, but also in those on subsequently fixated words.

During the last decade machine learning has spread rapidly in computer science and beyond, and a central issue for machine learning is data quality. This study was carried out in the intersection of business and Human-Computer Interaction, examining how an interface may be developed for crowdsourced verification of datasets.The interface is developed for efficiency and enjoyability through research on areas such as usability, information presentation models and gamification. The interface was developed iteratively, drawing from needs of potential users as well as the machine learning industry. More specifically, the process involved a literature study, expert interviews, a user survey on the Kenyan market and user tests. The study was divided into a conceptual phase and a design phase, each constituting a clearly bounded part of the study with a prototype being developed in each stage. The results of this study give an interesting insight on what usability factors are important when designing a practical tool-type mobile application, while balancing efficiency and enjoyability. The resulting novel interface indicated on a more effective performance than a conventional grid layout and is more enjoyable to use according to the users. In addition, the ‘rapid serial visual presentation’ can be deemed a well-functioning model for tool-type mobile applications which require a high amount of binary decisions on short time. The study highlights the importance of iterative, user-driven processes, allowing a new innovation or idea to merge with the needs and skills of users. The results may be of interest to anyone developing tool-type mobile applications and certainly if binary decision making on images is central. / Studien implementerar en utvecklingsprocess inspirerad av design thinking metodologi, och undersöker således gränslandet mellan ekonomi och människa-dator interaktion. Initialt undersöks affärsmöjligheter för mobila crowdsourcing applikationer i en Östafrikansk kontext, och baserat på resultaten av denna förstudie, utvecklas ett interface för mobil crowdsourcing. Interfacet ämnar hantera verifikation av bildbaserade dataset genom att samla in beslut från användarna. Målet var att designa för två huvudkriterier - njutbarhet och effektivitet, vilket uppnåddes genom efterforskning inom användbarhet, speed-reading metodologier och gamificationprinciper. Interfacet utvecklades iterativt, baserat på krav från potentiella användare, såväl som input från maskininlärningsindustrin. Mer specifikt involverade processen en litteraturstudie, expertintervjuer, en användarstudie på den Kenyanska marknaden och iterativa användartester. Den konceptuella fasen handlade om att identifiera problemet och leverera en relevant idé av hur lösningen skulle utformas. Således togs ett novellt ”Touch-Hold-Release”- interface fram. Resultaten av denna studie ger en intressant insikt i vilka usabilityfaktorer som är viktiga vid design av en praktisk arbetsinriktad applikation, samtidigt som effektivitet och njutbarhet balanseras. Det novella interfacet som tagits fram indikerar på en mer effektiv prestanda än den konventionella grid-layouten och är mer njutbar att använda enligt användarna. Dessutom kan ‘rapid serial visual presentation’ anses vara ett väl fungerande modell för arbetsinriktade mobilapplikationer som kräver stora mängder binära beslut på kort tid. Studien understryker vikten av att arbeta iterativt, med användarfokuserade processer som tillåter nya innovationer och idéer att möta användarnas faktiska behov och kunskaper. Resultaten kan vara av intresse för den som utvecklar en arbetsinriktad mobilapplikation och särskilt då binärt beslutsfattande är fundamentalt.

Anxiety can be advantageous in terms of survival and well-being, yet atypically high levels may be maladaptive and result in the clinical diagnosis of an anxiety disorder. Several risk factors have been implicated in the manifestation of clinical anxiety, including cognitive biases. In recent years, a plethora of research has emerged demonstrating that anxious adults exhibit biases of attention for threatening stimuli, especially that which is biologically relevant (e.g., facial expressions). Specific components of attentional bias have also been identified, namely facilitated engagement, impaired disengagement, and avoidance. However, the majority of studies have focused on the spatial domain of attention. Furthermore, the area is under-researched in children, despite research demonstrating that symptoms relating to clinical and non-clinical anxiety follow a stable course from childhood through to adolescence and adulthood. Consequently, the aim of this thesis was to investigate how anxiety affects children’s visual attention for emotive, particularly angry, faces. In order to provide a more comprehensive understanding, the current research involved examining the role of temporal and spatial attention utilising rapid serial visual presentation with the attentional blink, and the visual probe paradigm, respectively. The main hypothesis was that high state and/or trait anxiety would be associated with an attentional bias for angry, relative to positive or neutral faces in both the temporal and spatial domains. In relation to the temporal domain, key findings demonstrated that high levels of trait anxiety were associated with facilitated engagement towards both angry and neutral faces. It was further found that all children rapidly disengaged attention away from angry faces. Findings related to the processing of angry faces accorded with the main hypothesis stated in this thesis, as well as research and theory in the area. The finding that anxious children preferentially processed neutral faces in an attentional blink investigation was unexpected. This was argued to potentially reflect this stimulus type being interpreted as threatening. Key findings regarding the spatial domain were that high trait anxious children displayed an early covert bias of attention away from happy faces and a later, overt bias of attention away from angry faces. The finding that high trait anxiety was linked to an attentional bias away from happy faces in a visual probe task was also unexpected. This was argued to potentially reflect smiling faces being interpreted as signifying social dominance, thus resulting in the viewer experiencing feelings of subordination and becoming avoidant and/or submissive. To conclude, this thesis has enhanced current knowledge of attentional bias in both the temporal and spatial domains for emotive stimuli in anxious children. It has demonstrated that higher levels of trait anxiety moderate children’s allocation of attentional resources to different stimulus types, whether these are threatening, positive, or neutral. This has important implications for evaluating past research in adults and children, and for further developing theoretical models of attentional bias and anxiety. It also offers important clinical implications, since attending towards or away from specific stimuli may affect the development and maintenance of anxiety disorders. Recently, a treatment that aims to modify attentional bias in anxious individuals has begun to be developed. In light of the present findings, it may be necessary to review this treatment so that anxious children are re-trained in the specific biases of attention demonstrated here.

La chute chez les seniors constitue un problème de santé publique. Citée comme la seconde cause de décès accidentel dans le monde, elle concerne un tiers des Français de plus de 65 ans. Les séquelles physiques et fonctionnelles qui en résultent, les conséquences psychosociales nuisibles pour la qualité de la vie, la perte d’autonomie et son coût de prise en charge justifient l’attention qui lui est actuellement portée. Du point de vue du chercheur, les interprétations sous-jacentes à la surexposition des personnes âgées au risque de chute restent controversées, notamment parce que la compréhension de la coordination dynamique corporelle et de l’implication corticale lors du contrôle de l’équilibre est encore limitée. L’étude de la chute et des mécanismes qui y conduisent présente donc un double intérêt, fondamental et sociétal. Une chute survient si deux conditions sont réunies. La première est la perte initiale de l’équilibre, un ‘pré-requis’ qui peut toucher la population entière dans son quotidien. La seconde est un échec des mécanismes de rééquilibration, c’est à dire de la stratégie de réponse mise en œuvre pour compenser la déstabilisation : comment s’opère la sélection d’une stratégie de rattrapage, à partir de quelle appréciation du contexte et des informations sensorielles disponibles est-elle choisie ? qu’est ce qui assure son opérationnalité et garantit le rattrapage ou signe au contraire son échec ?...Pour répondre à ces questions, nous nous sommes donc intéressés à ce moment critique où il est encore possible de modifier l’issue finale par des ajustements posturaux et des actions motrices rapides et adéquats chez une population de jeunes adultes. La première étude est une analyse globale de la phase précoce d’une chute -abrégée par un harnais- (soit quelques centaines de millisecondes après la perturbation), afin d’évaluer la capacité du sujet à réagir à une perturbation imprévue et de développer des stratégies garantissant une protection efficace. Cette première étape se propose d’identifier les indicateurs discriminants et prédictifs d’une chute et d’un rattrapage au niveau neurophysiologique et biomécanique. Cette étude a également permis de mettre en évidence la présence d’un délai temporel incompressible appelé « phase passive », source de contraintes spatio-temporelles à l’expression complète d’une réponse posturale adaptée. Dans la seconde étude, de modélisation, nous avons élaboré un modèle mécanique personnalisé, construit à partir de radiographies tridimensionnelles non invasives du corps entier. Cette modélisation nous a permis d’analyser la contribution relative de propriétés biomécaniques passives et des synergies musculaires actives en jeu pendant les perturbations récupérables de l’équilibre ou non en comparant les résultats expérimentaux (‘réels’) obtenus à l’aide d’un dispositif asservi pour provoquer des chutes de plain-pied et la réponse théorique prédite (‘simulée’) à l’aide du modèle. Les résultats obtenus permettent de confirmer que le comportement du corps est en phase précoce-dicté par ses propriétés mécaniques, et peut être assimilé à un modèle simplifié. Après avoir mis en évidence l’existence d’une phase inertielle d’une durée équivalente à la moitié du temps disponible avant l’impact, notre questionnement s’est orienté vers le traitement de l’information en-cours lors de cette phase afin d’évaluer la contribution corticale alors que la réponse posturale évolue. La troisième étude consiste principalement à appréhender la charge cognitive impliquée dans le contrôle sensori-moteur, en particulier lors d’une chute, à l’aide du paradigme de double-tâche. En conclusion, à travers une approche pluridisciplinaire, les résultats obtenus dans cette thèse permettent d’émettre des recommandations intéressantes pour une prévention et une rééducation adaptée dans le but de contribuer à l’amélioration de la qualité de vie des personnes âgées. / A better understanding of what happens during an unintentional fall is relevant in preventing their occurrence. A fall is due to a failure of compensatory reactions to recover from postural perturbations during the descent phase which starts at the subject loss of balance point and lasts no more than 700-1000milliseconds [Hsiao, 1998]. The aim of the first study was to compare the biomechanical and muscular behavior during the pre-impact phase during non-recoverable falls and successful recovery trials. The experimental study aimed to evaluate the subject’s ability to distinguish in the first 500 milliseconds following the onset of perturbation a low-threatening perturbation from a high challenging one and can then predict the scenario that will more likely lead to a fall using specific motor strategies. In such a challenging task, we hypothesized that the constraints imposed by the biomechanical properties ultimately determine the ability to trigger efficient muscle activities. Full body 3D kinematics and associated muscle activities were collected in 30 young healthy subjects during fast and slow unpredictable multidirectional support-surface translations. 40 cm support-surface translations were used to evoke the balancing reactions (0,35 vs 0,9 m/s during resp. 1000 vs 500 millisecond The perturbation velocities were selected so that successful recovery should occur in milder trials whereas fast trials were sufficiently challenging to trigger non-recoverable falls. Analyses focused on the spatial and temporal characteristics of the Centre of Mass, angle variations, recovery step characteristics, and EMG activities (onset latencies and amplitudes) across each trial and muscle. Moreover, a 17-segment numerical and personalized model was created, based on stereoradiographic head to feet X-ray images followed by 3D-reconstruction methods to assess subject-specific geometry and inertial parameters. The outputs resulting from simulated falls allowed us to discard the contributions of the passive (inertia-induced) versus the active mechanisms (feedback-controlled and time-delayed neuromuscular components) of the response. The first outcome of that study was that the fall could be divided in distinct phases. For about 200 milliseconds following the onset of platform translation, the head remained stable in space. Similarly, the comparison with the simulated data supported that the CoM displacement matched the subject-dependant mechanical model. During a second phase of the fall, despite the fact that automated muscle postural synergies started at 80 milliseconds after perturbation onset, the trajectory of the body appeared to be exclusively dictated by its biomechanical properties. Later, muscle activities influenced the body trajectories, which consequently differed on a trial-to-trial basis. The simulation was in good agreement with the experimental results. The specificity of the postural response resulting in a strategy chosen to avoid a fall thus appeared in a late-phase, which can be explained because during a fall, the subjects had to prepare to the impact on the basis of sensory information that were not redundant but available in a sequential order: proprioceptive information appearing first while vestibular and visual information continued to signal a stabilized head in space. The sole proprioceptive information would be insufficient to trigger rapid and appropriate postural response. Moreover, in accordance with our results suggesting the importance of the late-phase and on-line controlled responses, a long inertial passive phase in the fast trials does not allow a large spatiotemporal window for compensatory reactions to occur. These could not only depend on the previously described automated postural synergies because the time constraints imposed by biomechanics permit in principle volitional motricity to play an important role very early in the fall. (...)