Dissertations / Theses: 'Visual attention in time'

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Jefferies, Lisa N. "Tracking attention in space and time : the dynamics of human visual attention." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/11564.

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Attention is essential to everyday life: without some selective function to guide and limit the processing of incoming information, our visual system would be overwhelmed. A description of the spatiotemporal dynamics of attention is critical to our understanding of this basic human cognitive function and is the primary goal of this dissertation. In particular, the research reported here is aimed at examining two aspects of the spatiotemporal dynamics of attention: a) the rate at which the focus of attention is shrunk and expanded along with the factors that influence this rate, and b) the factors governing whether attention is deployed as either a unitary or a divided focus. The present research examines the spatiotemporal dynamics of focal attention by monitoring the pattern of accuracy that occurs when participants attempt to identify two targets embedded in simultaneously presented streams of items. By asking participants to monitor these streams simultaneously, with the spatial and temporal positions of the two targets in the streams being varied incrementally, it is possible to index the extent of focal attention in both space and time. Chapter 2 develops this behavioural procedure and assesses the rate at which the focus of attention is contracted. A qualitative model is put forward and tested. Chapter 3 examines factors that modulate the temporal course of attentional narrowing in young adults who presumably can exercise efficient control of attentional processes. In contrast, Chapter 4 examines the effect of reduced attentional control by examining the same process in older adults. The second goal of this thesis was to examine whether focal attention is deployed as a unitary or a divided focus. These two perspectives are generally viewed as mutually exclusive. The alternative hypothesis pursued in Chapter 5 is that focal attention can be deployed as either a single, unitary focus or divided into multiple foci, depending on the observers mental set and on the task demands. The final chapter then combines and compares the findings across all experiments and evaluates how they fit in with current theories of visual attention.

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Sutton, Jennifer E. "Attention to time, space, and visual pattern by the pigeon." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0002/MQ30771.pdf.

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Braithwaite, Jason John. "Visual search in space and time : where attention and inattention collide?" Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269885.

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Azevêdo, Adriana Medeiros Sales de. "Mapeamento espacial da atenção visual mobilizada pela via visual ventral." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-25032010-145400/.

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O processamento visual se dá por duas vias, Dorsal (localização/movimento) mobilizada por TRS (tempo de reação simples), e Ventral (forma/cor) mobilizada por TER (tempo de reação escolha). Apresentamos uma nova abordagem para se investigar a distribuição dos recursos atencionais. Os métodos psicofísicos vigentes amostram repetidas vezes poucos pontos. Optou-se por amostrar muitos pontos na tela do computador poucas vezes, obtendo-se amostragem de uma grande área. Obteve-se um mapa de detalhamento da distribuição atencional. Experimentos de atenção voluntária: I. Tarefa de TRS, mobilizando a via Dorsal. Na situação de atenção difusa. II. TRE, mobilizando a via Ventral. Os estímulos possíveis diferiam na cor e foram respondidos ao se pressionar um botão, atenção difusa. III. TRE, focando-se a atenção em duas molduras, caracterizando atenção dividida. Os resultados demonstraram um favorecimento do hemicampo inferior para a TRS e um favorecimento do hemicampo superior para TER. Apareceram dois focos na atenção dividida fortalecendo a hipótese da divisão atencional. Visual processing has two pathways: Dorsal (localization/movement) mobilized for Simple Reaction Time tasks (SRT); Ventral (shape/color) mobilized for Choice Reaction Time tasks (CRT). We presented an approach to investigate visual attentional resources. Usual psychophysical methods sample many times few points. We opted to sample many points few times aiming to enlarge the sampled visual field. It was obtained major details of the attentional distribution. Voluntary attention task: I. SRT, for Dorsal pathway. Stimuli were different in color answered triggering a button, in a diffusion attention paradigm. II. CRT, for Ventral pathway. Stimuli were two different color answered by triggering a button for each color in a diffuse paradigm. III. CRT, experimental subject instructed to focus attention in two frames for a splitted attention paradigm. Results showed anisotropy in the diffuse attention distribution, favouring the lower hemifield for SRT and superior hemifield for CRT. The splitted attention paradigm evidenced the presence of two attentional focuses.

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Soares, Sandra C. "Fear commands attention snakes as the archetypal fear stimulus? /." Stockholm, 2010. http://diss.kib.ki.se/2010/978-91-7409-824-2/.

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Contenças, Thaís Santos. "É possível uma divisão da atenção visual automática no espaço?" Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-01072009-123939/.

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Existe controvérsia na literatura sobre a possibilidade de divisão espacial da atenção visual. Alguns autores encontraram evidências de que a atenção visual voluntária se divide no espaço. No entanto, a possibilidade de divisão da atenção automática ainda não foi adequadamente investigada. O objetivo deste trabalho foi investigar a possibilidade de uma divisão da atenção visual automática no espaço. Em um primeiro e segundo experimentos testamos a possibilidade da atenção automática se dividir em um mesmo hemicampo (esquerdo ou direito). Em um terceiro e quarto experimentos investigamos a possibilidade de divisão da atenção automática entre os hemicampos visuais (esquerdo e direito). Em conjunto, os resultados deste trabalho sugerem que a atenção automática pode se dividir entre os hemicampos visuais esquerdo e direito, mas em cada um destes hemicampos forma um foco único longo e estreito. Several studies demonstrated that voluntary visual attention can be divided. The possibility that this also occurs for automatic visual attention was investigated here. In the first and second experiments of this study the possibility of attention division in the same hemifield was examined. In the third and fouth experiments the possibility of attention division between hemifields was examined. The results suggest that automatic visual attention can not divide in the same hemifield but may divide between hemifields.

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Correani, Alessia. "Normal and abnormal attentional dwell time : constrains of temporal coding in visual attention in neurological patients and normal individuals." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1781/.

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This thesis is concerned with the analysis of constrains of temporal coding in visual selective attention. It is well known that despite the great amount of visual information present in the environment the human visual system is only capable to attend and select some of it. How the brain is able to selectively prioritize relevant information and de-prioritize the irrelevant information in order to guide us through space, has been extensively investigated (Treisman and Gelade, 1980; Posner, 1980). Less is known about how this occurs over time. In the present thesis I investigate the role of temporal limitation of selective attention in brain damaged patients and in normal participants by using a simplified version (attentional dwell time paradigm, Duncan et al., 1994), of the Attentional Blink (AB) paradigm which involves the identification of two or more visual targets when stimuli are presented rapidly in temporal succession always at one location (Broadbent and Broadbent, 1987; Raymond, Shapiro and Arnell, 1992). Within this paradigm I have manipulated different factors which may influence this limitation such as: temporal binding, perceptual similarity among stimuli, task switching, integration of audio-visual information and working memory. In addition, by examining the AB in different brain lesioned groups, this thesis attempts to throws light on the neural mechanisms underlying temporal coding and selection. Evidence was provided of the influence of all these mechanisms in coding, selecting and consolidating visual information over time which suggest a multi components nature of temporal selection as well as possible involvements of a temporo-parietal network (Corbetta and Shulman, 2002) which governs their integration.

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Montassier, Ana Beatriz Sacomano. "Atenção visual em crianças e adolescentes com distúrbio de aprendizagem." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/25/25143/tde-04122013-091051/.

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A atenção encontra-se incluída no grupo de funções psíquicas, agrupadas sob o nome de funções cognitivas que subsidiam o processo de aprendizagem escolar. Em relação à atenção visual, a literatura vem apontando a existência de diferenças no tempo de reação a estímulos visuais entre escolares com e sem distúrbios de aprendizagem (DA). Neste sentido, o objetivo deste estudo foi caracterizar a função atencional visual em escolares com DA. Participaram deste estudo 50 escolares, sendo 25 com o diagnóstico de distúrbio de aprendizagem, formando o grupo de estudo (GE), e 25 crianças sem queixas escolares, formando o grupo controle (GC), com faixa etária entre oito e 14 anos de idade. Os instrumentos utilizados foram o Teste de Atenção Visual (TAVIS4), um teste computadorizado composto por três tarefas para avaliar a capacidade atentiva de sustentar, selecionar e mudar o foco de atenção para estímulos visuais e da impulsividade motora, e a Escala de Conners na forma abreviada para professores, apropriado para discriminar crianças com problemas de comportamento e com sintomas de TDAH. Os resultados evidenciaram que o tempo de reação médio (TRM) do GC foi significativamente menor que o do GE na tarefa de atenção sustentada. O GE também apresentou diferença estatística significativa na atenção alternada, com menor número de acertos (NA), maior número de erros por omissão (EO) e maior número de erros por ação (EA). Na Escala de Conners a pontuação do GE foi maior do que do GC. Houve correlação entre os testes nas tarefas de atenção alternada e nas tarefas de atenção sustentada para o número de acertos (NA), erros por omissão (EO) e erros por ação (EA). Podemos inferir que as crianças com DA apresentam déficit dos processos atencionais, embora não possam ser caracterizadas com o TDAH. No subgrupo dos adolescentes houve diferença significativa na atenção seletiva para o número de erros por omissão (EO), no TRM da atenção sustentada e na atenção alternada para número de erros por omissão (EO) e erros por ação (EA). Houve correlação entre os testes, neste subgrupo do GE e GC na atenção seletiva para o número de acertos (NA), erros por omissão (EO) e erros por ação (EA). Portanto, os maiores índices apontados na escala (déficit atencional) estão associados aos piores resultados dos participantes nas tarefas de atenção alternada e sustentada. Pode-se observar que quanto maior a idade dos participantes, melhor é a capacidade de atenção seletiva, sustentada e alternada. Desta maneira, o TMR mais baixo do subgrupo dos adolescentes em comparação com o grupo geral pode evidenciar a melhora da atenção com o desenvolvimento. Porém, os adolescentes do GE apresentaram melhor desempenho do que as crianças, ou seja, algumas alterações notadamente persistem quando comparadas ao GC sugerindo uma disfunção dos mecanismos neuropsicológicos subjacentes ao processamento da atenção visual nos adolescentes com DA. Attention is included in the group of psychic functions, grouped under the name of cognitive functions, and that support the learning process in school. Regarding the visual attention, literature has pointed to the existence of differences in reaction time to visual stimuli between students with and without learning disabilities (LD). In this sense, the purpose of this study was to characterize the visual attentional function in children with LD. A total of 50 students, including 25 with learning disorders without signs of Attention Deficit Disorder and Hyperactivity Disorder (ADHD), forming the study group (SG), and 25 children without impairments, forming the control group (CG) , aged between eight and 14 years old. The instruments used were the Test of Visual Attention (TAVIS4), computerized test consists of three tasks to assess the ability to sustain attentional, select and change the focus of attention to visual stimuli and motor impulsivity, and the Scale of the Conners abbreviated form for teachers, appropriate to discriminate children with behavior problems and ADHD signs. The results showed that the hit reaction time (HRT) of the CG was significantly less than the SG in the sustained attention task. SG also showed statistically significant differences in the alternating attention, with less number of right answers (RA), higher number of omission errors (OE) and higher number of commissions errors (CE). Scale of the Conners scores of GE was higher than the GC. There was a correlation between tests in alternating attention tasks and sustained attention tasks to the number of right answers (RA), omission errors (OE) and commission errors (CE). We may deduce that children with LD have deficits of attentional processes, although they cannot be characterized with ADHD. In the subgroup of adolescents was significant difference in selective attention to the number of omission errors (OE), the HRT of sustained attention and alternating attention to the number of omission errors (OE) and commission errors (CE). There was a correlation between tests, this subgroup of SG and CG in selective attention to the number of right answers (RA), omission errors (EO) and commissions errors (CE). So, the highest rates indicated on the scale (attentional deficits) are associated with worse outcomes of participants in the tasks of sustained and alternating attention. It can be observed that the higher the age of the participants, the better the ability of selective attention, sustained attention and alternating attention. That way, the HMT less subgroup of adolescents compared with the overall group may show an improvement in attention to development. However, adolescents SG improved their attentional capacity, but some changes persist especially when compared to CG suggesting a dysfunction of neuropsychological mechanisms underlying the processing of visual attention in adolescents with LD.

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Righi, Luana Lira. "Características do efeito da atenção intermodal automática." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-17042013-105052/.

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O presente trabalho analisou algumas das possíveis características do efeito da atenção intermodal entre elas: relação sinal/ruído e assincronia entre início dos estímulos (AIE) em relação ao tipo de tarefa realizada. Os Experimentos 1 e 2 mostraram que os efeitos da atenção intermodal se manifestam na presença de ruído visual externo, e que não se manifestam na ausência de ruído em uma AIE de 133 ms. No entanto, o Experimento 3 mostrou que quando a AIE é maior que a utilizada nos experimentos anteriores, o efeito intermodal se manifesta no comportamento na ausência de ruído visual externo. Finalmente, o Experimento 4 mostrou que em uma AIE curta (133 ms), e em uma tarefa de localização, o efeito intermodal se manifesta. Os resultados sugerem que o efeito atencional intermodal se manifesta na presença e na ausência de ruído visual e que o mecanismo de discriminação da frequência do alvo demora mais tempo para se completar do que o mecanismo de localização do alvo. The current work examined the possible contribution of signal to noise ratio, the asynchrony between the onsets of the cue and the target (SOA) and the kind of task performed by the observer to the manifestation of crossmodal attentional effects. The Experiments 1 and 2 showed that crossmodal attentional effect appears when there is visual noise, but it does not appear when there is no visual noise at 133 ms SOA. The Experiment 3 showed that when the SOA is longer than 133 ms, the crossmodal attentional effect appears when there is no visual noise. The Experiment 4 showed that in a localization task, the crossmodal attentional effect appears even in a short SOA (133 ms). Taken together, the results indicate that crossmodal attentional effects appear when there is visual noise and when there is no visual noise. However, in the later condition and when the target has to be identified, the crossmodal attentional effect takes longer to appear.

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Li, Hui. "Experiments on the dynamics of attention: Perception of visual rhythm and the time course of inhibition of return in the visual field." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-172019.

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How attention is controlled is one of the challenging topics in cognitive neuroscience and psychology. For spatially represented targets in the visual field it has been shown that some features of visual stimuli like different colors instantaneously ‘pop-out’, while others require a serial search which is conceived of as an effortful task. It is an open question whether dynamic feature of a stimulus are processed instantaneously without high attentional demand or serially with high demand. This question was studied in experiments on rhythm perception with periodically moving stimuli, and a visual search paradigm was employed. The search display consisted of vertically moving dots with regular rhythms; one dot however moved with a different period, and this dot with a longer or shorter period had to be detected as fast as possible. To make the period of the movement a critical target, amplitudes and phases of the distractors were randomized. It was observed that the perception of a visual rhythm defined only by the period does not lead to a pop-out effect. Apparently, the conjunction of period, equal phase and equal amplitude of movements are necessary for an effortless processing of visual rhythms. Interestingly, a faster rhythm compared to the distractors was detected with shorter reaction times. In additional experiments, it was for instance shown that auditory information supports the extraction of rhythmic visual targets indicating an intermodal mechanism. In another experimental set-up it was tested whether the attentional machinery is controlled by a common temporal mechanism. Experiments on ‘inhibition of return’ (IOR) have indicated that attentional control in the peri-foveal region of the visual field underlies a different neuronal mechanism compared to the periphery of the visual field. This eccentricity effect of IOR raises the question, whether attentional control for the visual periphery is characterized by a longer time constant as the peripheral inhibitory control is much stronger. Experimental evidence indicates, however, that the two attentional systems share the same time window of approximately three seconds. These observations support the notion of a functional subdivision of the visual field which is overcome, however, by a common temporal control mechanism. Wie Aufmerksamkeit kontrolliert wird, ist eine der besonderen Herausforderungen in den kognitiven Neurowissenschaften und der Psychologie. Für räumlich repräsentierte Reize konnte gezeigt werden, dass bestimmte Aspekte visueller Reize wie verschiedene Farben sofort hervorstechen („pop-out“), während für andere Reize serielle Such-Strategien notwendig sind, die also mentalen Aufwand erfordern. Es ist eine offene Frage, ob dynamische Merkmale von Reizen ohne besonderen Aufwand verarbeitet werden, oder ob serielle Prozesse erforderlich sind, um sie zu erkennen. Diese Frage wurde in Experimenten über Rhythmus-Wahrnehmung mit periodisch sich bewegenden Reizen untersucht, und ein visuelles Such-Paradigma wurde angewandt. Es wurden auf einem Display vertikal sich bewegende Punkte gezeigt, wobei einer der Punkte sich mit einer anderen Periode, schneller oder langsamer, bewegte, und diese Punkte mussten so schnell wie möglich erkannt werden. Um nur die Periode als kritische Variable zu untersuchen, wurde die Phase und die Amplitude der anderen Reizpunkte randomisiert. Es wurde festgestellt, dass die unterschiedliche Periode allein nicht zu einem „pop-out“-Effekt führt. Damit ein abweichender, sich bewegender dynamischer Reiz erkannt wird, müssen offenbar Periode, Phase und Amplitude übereinstimmen. Reize mit einer kürzeren Periode als die Hintergrundreize wurden deutlich schneller erkannt. In weiteren Experimenten konnte beispielsweise gezeigt werden, dass akustische Information die Extraktion rhythmisch sich bewegender visueller Reize deutlich verbessert, was auf intermodale Effekte hinweist. In einer weiteren Studie wurde untersucht, ob die neuronale Aufmerksamkeits-Maschinerie gemeinsamen zeitlichen Prinzipien gehorcht. Versuche zum Phänomen des „Inhibition of Return“ (IOR, Hemmung der Aufmerksamkeits-Wiederkehr) haben ergeben, dass die Mechanismen der Aufmerksamkeits-Steuerung im perifovealen Bereich anderen Gesetzen gehorchen als in der Peripherie des Gesichtsfeldes. Dieser „Ekzentrizitäts-Effekt“ wirft die Frage auf, ob die zeitlichen Prozesse der Aufmerksamkeits-Kontrolle in der Peripherie durch längere Zeitkonstanten gekennzeichnet sind, da die inhibitorische Kontrolle dort ausgeprägter ist. Es zeigt sich allerdings, dass die beiden Aufmerksamkeits-Systeme das gleiche Zeitfenster von etwa drei Sekunden nutzen. Diese Beobachtungen stützen das Konzept der funktionellen Inhomogenität des Gesichtsfeldes, die aber durch einen gemeinsamen zeitlichen Mechanismus in eine kognitive Einheit gebracht wird.

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Herath, Priyantha. "Functional neuroimaging of dual task interference and divided attention /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-232-9.

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Sais, Fernanda Amadei. "Por que locais demarcados são importantes para o aparecimento do efeito atencional automático?" Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-22072011-141927/.

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Investigamos, no Experimento, se o estímulo precedente, que captura a atenção quando existem demarcações, deixa de capturar a atenção na ausência de demarcações por ter seu processamento filtrado precocemente. Além disso, investigamos, nos experimentos 2, 3 e 4, se alterações no fundo da tela, que gerassem maior competição no processamento dos estímulos presentes na cena visual, poderiam levar à captura da atenção, mesmo sem a presença das demarcações classicamente utilizadas. Observamos que quando a intensidade dos estímulos competidores presentes na tela era alta, o estímulo precedente passou a capturar a atenção. Explicamos esse resultado com a hipótese de que as demarcações são importantes por adicionarem ruído ao processamento dos estímulos apresentados, influenciando a representação desses estímulos e, portanto, a possibilidade de um estímulo capturar a atenção. Por fim, no Experimento 5, investigamos se os resultados da tarefa de escolha de local seriam replicados em uma tarefa de discriminação de forma. In Experiment 1 we investigated if a peripheral stimulus, which is able to capture attention when there are placeholders on the screen, is no longer able to capture attention in the absence of placeholders because is early filtered. In Experimento 2, 3 and 4 we investigated if changes on screen background, which would generate stronger processing competition between stimuli, could lead to attentional capture even in absence of placeholders. Accorging to our results the peripheral stimuli is able to capture attention when competing stimuli of high intensity are presented togueter on screen. Our explanation is that placeholders are important because they add noise to stimuli processing, affecting stimuli representation and, therefore, the probability that a stimulus will capture attention. Lastly, in Experimento 5 we investigated if similar results would be obtained in a form discrimination task.

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Bomfim, Geisa Cristina Ost Eburneo do. "Avaliação da atenção visual ao longo do turno de trabalho em atividade repetitiva." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-01112007-132231/.

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Durante o turno de trabalho em atividades repetitivas, foram avaliados 8 homens com idade entre 20 e 40 anos, com cronotipo moderadamente matutino, e dominância manual e visual direita. Os sujeitos foram submetidos a testes de alocação da atenção visual 6 vezes ao dia, em 9 dias. Os testes consistiam em manter o olhar fixo no centro da tela do computador, e responder o mais rapidamente possível a todos os estímulos que aparecerem. No experimento 1 (atenção explícita) devia-se prestar particular atenção à área de 4ox4o centrada no ponto de fixação, no experimento 2 (atenção dividida) devia-se prestar atenção simultaneamente a duas regiões de 4ox4o centradas lateralmente, a 10 o do centro. Os voluntários executaram a primeira tarefa sem problemas durante todo o turno de trabalho, com TRs médios mais rápidos no início da manhã (7h40min), e no início da tarde (14h20min). Quanto aos testes de atenção dividida, houve uma aparente oscilação no desempenho médio dos sujeitos a cada uma hora e vinte, com TRs mais rápidos nos mesmos horários (7:40 e 14:20). During their worshift with repetitive activity, we evaluated 8 male subjects between 20 and 40 years old, right eye and hand dominance, and with moderate morningness chronotype. The subjects were submitted to tests of allocation of visual attention on 9 days. Tests consisted of fixing the point center of a computer screen and pressing a key as quickly as possible to any stimulus that they appeared anywhere on the screen. In experiment 1 attentioni should be focussed in a 4ox4o central area, whereas in experiment 2, attention should be divided simultaneously sideways, in two such 4ox4o areas, indicated by two lateral squares frames. Subjects easily focused attention in the center (experiment 1) throughout their workshift, whit quicker average of reaction times (RTs) at the beginning of the morning (7h40min), and at the beginning in the afternoon (14h20min). There was, on the other hand, an apparent oscillation in their ability to divide attentio with period of approximately 80 min. Again, mean RTs were faster at 7:40 and again at 14:20.

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Righi, Luana Lira. "Assimetria interlateral da atenção visuoespacial automática em tarefas de discriminação de forma e de localização." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-02042009-114350/.

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Há evidências de que a orientação da atenção para o lado direito seria mais eficiente do que para o esquerdo. Outros trabalhos mostram uma assimetria quanto às vias visuais. A via ventral, que realiza processamento de objetos, seria mais ativa no hemisfério esquerdo e a via dorsal, que realiza a localização de estímulos, seria mais ativa no hemisfério direito. A interação entre essas assimetrias foi investigada. Realizamos dois experimentos nos quais a atenção automática dos sujeitos foi mobilizada através do aparecimento de um estímulo visual periférico. O Experimento 1 foi uma tarefa de discriminação de forma, envolvendo a via ventral. O Experimento 2 foi de discriminação de local, envolvendo a via dorsal. Esperávamos a manifestação de uma assimetria comportamental para o lado direito apenas no Experimento 1. No entanto isto ocorreu nos dois experimentos, ou seja, assimetria foi para o lado em que a atenção é preferencialmente mobilizada. O que sugere que o fator determinante para essa manifestação é a assimetria atencional, mas não assimetria das vias visuais. Recent studies have shown that attention orienting to the right side is more efficient than attention orienting to the left side. Other studies have shown that the two hemispheres process visual stimuli differently: the ventral visual pathway, which processes object shape, is more active in the left hemisphere, while the dorsal visual pathway, which processes object location, is more active in the right hemisphere. This work investigated theses asymmetries. Automatic attention was mobilized by a peripheral visual prime stimulus in two experiments. In Experiment 1 a task requiring shape discrimination was used. It was expected a strong bias to the right side. In Experiment 2 a task requiring location discrimination was used. It was expected now a much smaller bias to the right side. A strong bias to the right side was found in the two experiments. This bias was probably due to the attentional bias to the right side. Interhemispheric sensory asymmetries apparently were not strong enough to influence behavior in the present experimental conditions.

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Astrand, Elaine. "Real-time readout of neural contents in visual perception and selection in the non-human primate." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10215.

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Un accès aux représentations mentales. Voici une phrase qui pourrait bientôt devenir une réalité. La recherche sur les interfaces cerveau-Machines est un champ de recherche en plein essor. En particulier, de grandes avancées ont été réalisées pour permettre par exemple à des tétraplégiques de retrouver une relative autonomie en actionnant un bras robotique par l'activité de leur cerveau. L'équipe de Hochberg a mis en évidence un système permettant à une femme tétraplégique d'attraper une boisson et de boire. Cela montre la précision incroyable que peut avoir une prothèse artificielle pilotée par le cerveau. Ma thèse porte sur un aspect peu exploré des interfaces cerveau-Machines, celui des interfaces cerveau-Machines cognitives, c'est-À-Dire utilisant le contenu représentationnel intime de l'activité du cerveau. Son objectif est de démontrer, sur un modèle primate non-Humaine, la possibilité d'accéder en temps-Réel à ce type de contenu complexe, y compris dans un environnement en perpétuel changement. L'adaptation des interfaces cerveau-Machines dans le monde réel, où nous sommes constamment confrontés à de nouvelles informations, est critique pour son fonctionnement. Un autre aspect, très important, porte sur l'exploration et la compréhension du système nerveux au niveau populationnel en utilisant des méthodes similaires à celles utilisées pour extraire de l'information dans les interfaces cerveau-Machines. Cela nous permet d'étudier le contenu instantané et sa dynamique dans l'évolution du temps. En résumé, nous démontrons la faisabilité d'accéder en temps-Réel à des informations complexes de l'attention spatiale et de la perception visuelle. Cet accès en temps-Réel n'est que peu affecté par un environnement qui change. Le potentiel de ce type d'interfaces cerveau-Machines est immense en vue du traitement de pathologies neurologiques aigües (suite à des accidents cérébraux vasculaires ou suite à des traumatismes accidentés) ou neurodégénératives (dans la maladie d'Alzheimer ou de Parkinson, pour ne parler que des plus connues) The field of invasive Brain Machine Interfaces (iBMI) has during the last ten years proven its enormous potential in restoring movements in paralyzed patients. The present doctoral thesis introduces a new dimension to this field by using complex cognitive behavior to drive an iBMI. In this respect, visual processes including spatial attention and perception are of special interest. This thesis project has three principal objectives: first, show the feasibility of decoding cognitive information in an offline setup. Second, evaluate the decoding of cognitive information in a real time experimental setup and third, investigate the impact of this setup in a changing environment, this both from the perspective of driving real time brain-Machine interfaces and that of understanding distributed populational neuronal codes. In line with the first objective of this thesis, an evaluation of several different classification techniques has been carried out in order to choose the best suited method for reading out cognitive information. The study provides evidence that visual information can be read out with similar performance as cognitive information. This study is the first study aiming at explicitly comparing the read out of sensory and cognitive information. The two last objectives of the present thesis are carried out on data from a new real-Time experimental setup. First we demonstrate the feasibility of real-Time readout of spatial attention and perception and we bring about a novel understanding about these two cognitive processes. Second, we show that in a changing environment, remarkable reconfigurations of prefrontal neural populations occur under certain contexts while left unaffected by other contexts. This Ph.D. thesis has taken the field of cognitive brain-Machine interfaces one step further by establishing the impact on spatial attention and perception of a changing environment. Facing the many neurological and neurodegenerative pathologies existing today, this thesis provides a steady ground for the continuation of research in this area

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Dias, Fabrício Bacchini. "O efeito da carga perceptual sobre pistas periféricas em uma tarefa vai/não vai." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-10072014-154339/.

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Resultados anteriores de nosso laboratório em tarefas de tempo de reação vai/não-vai utilizando uma pista periférica sugerem que a presença do efeito atencional depende da saliência do alvo em relação ao distraidor. O objetivo deste trabalho foi examinar e estender esses resultados assumindo a hipótese de que a interferência de estímulos irrelevantes é menor em condições de alta carga perceptual. No experimento 1, confirmando resultados anteriores, registramos o efeito atencional quando o alvo era uma linha vertical e o distraidor era uma linha horizontal, porém, quando esses estímulos desempenhavam papel oposto, não houve mobilização da atenção. Supusemos que uma maior saliência perceptual da linha vertical em relação à linha horizontal pode ter sido o fator responsável pela ausência do efeito atencional quando a linha vertical assumiu o papel de distraidor. Testamos essa hipótese nos experimentos 2 e 3, onde removemos o distraidor e diminuímos sua saliência, respectivamente. Nos dois casos, registramos o efeito atencional para a linha horizontal. Esse resultado é consistente com a hipótese de menor saliência perceptual da linha horizontal em relação à vertical e também com a hipótese da carga perceptual. O objetivo do experimento 4 foi identificar um dos possíveis fatores responsáveis pela menor saliência da linha horizontal. Replicamos o experimento 1, porém diminuindo a luminosidade da tela, para testarmos um possível efeito de enquadramento, e obtivemos o efeito atencional, como previsto. Porém, ao repetirmos o mesmo experimento, aumentando a saliência dos distraidores, registramos o efeito atencional apenas na condição em que o alvo era a linha vertical. Embora os fatores responsáveis pela maior saliência relativa da linha vertical ainda não estejam claros, o conjunto de resultados corrobora a hipótese de que o processamento da pista é prejudicado em condições de maior carga perceptual. Previous studies from our laboratory suggest that the presence of the attentional effect in go/no-go reaction time tasks using a peripheral cue depends on the salience of the go target stimulus in relation to the distactor. The aim of this study was to examine and extend these results, assuming the hypothesis that there is less interference of irrelevant stimuli during conditions of high perceptual load. In experiment 1, we obtained an attentional effect when the go target was a vertical line and the distractor was a horizontal line, but no effect when the go target was the horizontal line and the distractor was the vertical line. We suggested that a greater perceptual salience of the vertical line relative to the horizontal line might be the factor responsible for the absence of the attentional effect when the vertical line was the distractor. We tested this hypothesis in experiments 2 and 3, where we removed the distractor and reduced its salience, respectively. In both cases, we observed an attentional effect for the horizontal line. This result is consistent with the hypothesis of greater salience of the vertical line relative to the horizontal line and also with the perceptual load hypothesis. The aim of experiment 4 was to identify a possible factor responsible by the smaller perceptual salience of the horizontal line. We replicated experiment 1, but reducing the luminosity of the monitor screen, as a test for a possible framing effect, and obtained an attentional effect as expected. However, when we repeated the same experiment, raising the perceptual salience of the distractors, we observed an attentional effect only when the vertical line was the go target. Although the factors responsible for the greater perceptual salience of the vertical line relative to the horizontal line are not clear yet, our results support the hypothesis that the sensory processing of the cue is reduced in conditions of higher perceptual load.

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Grove, Kevin. "Evaluation of Package Delivery Truck Drivers: Task Analysis and Development/Validation of an Objective Visual Behavior Measure to Assess Performance." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33345.

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The job of a package delivery driver (PDD) is complex and demanding. These drivers must possess many skills in order to succeed in their work, including physical stamina, appropriate decision-making, positive customer interaction, and most importantly, operational safety. Companies must use significant resources, not only to provide insurance for existing drivers, but also to train new drivers to use their visual attention effectively while driving, and companies have a vested interest in ensuring that the most capable trainees are selected for jobs. Currently, subjective assessments of supervisors or managers are typically used to make these determinations. While these are valuable methods for assessing drivers, an objective measure of how well the driver is using his/her visual attention would both assist evaluators in making judgments, as well as make those judgments more accurate. The purpose of the study described herein was to 1) conduct a task analysis of the driving component of the PDD job responsibilities, and 2) create and test an objective measure that a package delivery company could use to evaluate the performance of its drivers. A detailed task analysis based on numerous observations of drivers in their normal work routines was conducted for this research in order to understand these complex tasks. A framework was created for understanding this system of tasks, which was then used to organize all tasks that drivers were observed to perform into more general, goal-oriented activities. Using this task analysis, incidents were identified that were observed while drivers were behind the wheel. This information demonstrated that breakdowns were occurring within the tasks drivers were performing and that improved methods of training and evaluations may be needed as a result. A construct of visual behavior called Head Down Time (HTD) was then created and tested. An individual HDT is defined as the sum of time of all eye gazes away from the primary display (i.e. windshield) between two distinct eye gazes at the primary display while the vehicle is in motion. HDT was evaluated for its ability to differentiate levels of experience between drivers, its relationship to types of route on which drivers delivered, and its relationship to the driving-related incidents that were observed. HDTs were shown to be differed significantly between drivers of low and high experience, with experienced drivers displaying shorter durations of HDT when compared to inexperienced drivers. HDTs also differed in duration when analyzed by the type of route upon which drivers operated. Commercial and urban routes, while not significantly different with respect to HDT, were shown to have increased HDT durations when compared to rural routes and, in turn, residential routes were found to have significantly longer HDTs than did rural routes and may have significantly shorter durations compared to commercial and urban. Finally, HDTs that were associated with observed driving incidents in terms of chronological proximity were shown to be of significantly longer duration than were HDTs that were not associated with incidents. All tests were conducted using appropriate statistical measures, including t-tests at a level of Î± = 0.05 for each dataset. Applications of this research include: 1) improvement of PDD training and evaluation methods through use of a detailed task analysis, 2) improvement in how package delivery companies define incidents and train PDD toward the prevention of incidents based on task analysis and observations as to incident frequency, and 3) the further development of HDT as a possible objective measure to supplement the training and evaluation of PDD. Master of Science

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Gaume, Antoine. "Towards cognitive brain-computer interfaces : real-time monitoring of visual processing and control using electroencephalography." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066137/document.

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Les interfaces cerveau-machine (ICM) ouvrent des voies de communication alternatives entre le cerveau et son environnement. Elles peuvent être utilisées pour supplanter une fonction biologique défaillante ou pour permettre de nouveaux modes d’interaction à l’utilisateur. Les ICM de sortie, dont le fonctionnement se base sur la lecture de données biologiques, nécessitent la mesure de signaux de contrôle stables dans le temps et dans la population. La recherche de tels signaux et leur calibration sont des étapes clefs dans la conception d’une ICM. Cette étude s’intéresse en premier lieu aux ICM utilisant les potentiels évoqués visuels comme signaux de contrôle. Un modèle est proposé pour la prédiction individuelle de ces potentiels en régime permanent, c’est-à-dire lorsqu'ils sont issus d’une stimulation périodique. Ce modèle utilise une sommation linéaire corrigée en amplitude de la réponse à des stimulations visuelles discrètes pour prédire quantitativement la nature et la localisation spatiale de la réponse à des stimulations répétées. Les signaux modélisés sont ensuite utilisés en temps réel comme base de comparaison pour décoder les signaux électroencéphalographiques d’une ICM. Dans une deuxième partie, un paradigme est proposé pour le développement d’ICM cognitives, c’est-à-dire permettant la mesure de fonctions cérébrales de haut niveau. L’originalité du paradigme réside dans la volonté de mesurer la cognition en continu plutôt que son influence sur des événements discrets. Une expérience visant à discriminer différents états d’attention visuelle soutenue est proposée, avec l’ambition d’une mesure en temps réel pour le développement de systèmes de neurofeedback Brain-computer interfaces (BCIs) offer alternative communication pathways between the brain and its environment. They can be used to replace a defective biological function or to provide the user with new ways of interaction. Output BCIs, which are based on the reading of biological data, require the measurement of control signals as stable as possible in time and in the population. Identification and calibration of such signals are crucial steps in the conception of a BCI.The first part of this study focuses on BCIs using visual evoked potentials (VEPs) as control signals. A model is proposed to predict steady-state VEPs individually, i.e. to predict the response of a given subject’s brain to periodic visual stimulations. This model uses a linear summation of transient VEPs and an amplitude correction for quantitative prediction of the shape and spatial organization of the brain response to repeated stimulations. The simulated signals are then used as a basis of comparison for real-time decoding of electroencephalographic signals in a BCI.In the second part of this study, a paradigm is proposed for the development of cognitive BCIs, i.e. for the real-time measuring of high-level brain functions. The originality of the paradigm lies in the fact that correlates of cognition are measured continuously, instead of being observed on discrete events. An experiment with the purpose of discriminating between several levels of sustained visual attention is proposed, with the ambition of real-time measurement for the development of neurofeedback systems

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Li, Hui [Verfasser], and Ernst [Akademischer Betreuer] Pöppel. "Experiments on the dynamics of attention: Perception of visual rhythm and the time course of inhibition of return in the visual field / Hui Li. Betreuer: Ernst Pöppel." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1055907556/34.

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Canto-Pereira, Luiz Henrique Mourão do. "Mapeamento espacial da atenção visual através de tempos de reação: um estudo psicofísico." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/47/47135/tde-21122006-125608/.

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Nos últimos vinte e cinco anos a atenção visual tem sido descrita em termos de diversas metáforas, salientando-se o holfote atencional, a lente zoom e o gradiente atencional. Um aspecto essencial dessas metáforas é a distribuição dos recursos atencionais no campo visual, que não é necessariamente determinado pelo ponto de fixação e que pode depender tanto de eventos externos como também de estados mentais. Esse estudo apresenta uma abordagem inovadora, baseada em tempos de reação analisados através de métodos geoestatísticos, para investigar como a atenção visual se distribui em áreas extensas do campo visual. Cinco diferentes experimentos foram realizados: no experimento I participantes foram solicitados a não atender nenhuma região em particular do espaço (da tela do computador) caracterizando assim a atenção difusa. Nos demais experimentos, os participantes foram solicitados a direcionar a atenção explicitamente ao centro (expt. II); de maneira encoberta para esquerda (expt. III) ou para direita (expt. IV); ou dividindo a atenção em duas regiões tanto a direita como a esquerda simultaneamente, mas não para o centro (expt. V). A distribuição espacial da atenção, medida através de tempos de reação, foi obtida na forma de mapa de pixieis resultante da análise geoestatísica. O experimento I teve como resultado um favorecimento atencional do quadrante nasal do hemicampo inferior. O experimento II, como esperado, apresentou um foco atencional coincidente com o ponto de fixação. Os experimentos III e IV mostraram claramente focos atencionais para esquerda e direita, respectivamente. Por fim o experimento V mostrou dois focos atencionais, à esquerda e direita, indicando divisão atencional. Esses resultados demonstram a utilidade da geoestatística para a análise de tempos de reação no estudo da atenção visual. O método também forneceu evidências claras da possibilidade de dividir a atenção visual à direita e à esquerda do ponto de fixação, um tema ainda controverso na literatura. In the past twenty five years visual attention has been described in terms of varied metaphors, among which a spotlight, a zoom lens and a gradient field. An essential aspect of all these metaphors is the distribution of attentional resources in the visual field, which is not necessarily determined by the fixation point, and may depend on both external events and internal mental processes. This study presents a novel approach, based on reaction times and analyzing data with geostatistical techniques, to investigate how visual attention is allocated in large continuous regions of space. Five different experiments were performed: in experiment I participants were asked not to attend to any particular region, but rather try to spread their attention as uniformly as possible over the computer screen (diffuse attention). In the remaining experiments, participants were instructed to direct their visual attention overtly towards the center (expt. II), or covertly to the left (expt. III) to the right (expt. IV), or to divide their attention attending regions both right and left (but not to the center (expt. V). The spatial distribution of attention, as evaluated through reaction times, was obtained in the form of pixel maps resulting from the geostatistical analysis. Experiment I showed a lower hemifield advantage, in the nasal quadrant. Experiment II, as expected, presented an atentional focus coincident with the fixation point. Experiments IV and V showed clear attentional foci, to the left and to the right, respectively. Finally, Experiment V showed two clear lateral foci, one to the left, the other to the right, indicating attentional division. These results demonstrate the usefulness of geostatistics to analyze reaction time data for the study of visual attention. The method also provided clear evidence for the ability of subjects to divide their visual attention in two well separated foci, to the right and to the left of their fixation point, an issue still debated in the literature.

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Sant\'Ana, Marília Martino de. "Tempos de reação e atenção visuo-espacial mobilizada voluntariamente em atletas e não atletas." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-20092013-102224/.

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Existe interesse crescente em informações científicas sobre o papel da percepção visual e da atenção visuo-espacial nos esportes. Comparamos os Tempos de Reação (TR) de atletas profissionais com os de não atletas em 5 condições de atenção visual voluntária: difusa, manifesta, encoberta (à esquerda e à direita do ponto de fixação) e dividida. Os atletas apresentaram TR médios menores que os não atletas em todos os experimentos. Diferenças em TRs a estímulos visuais dentro e fora dos focos atencionais não foram significativas (p>0,31), exceto na condição de atenção manifesta (p=0,0001), mas foram ligeiramente maiores em atletas. Tais diferenças foram significativas em experimentos com outros grupos de interesse do nosso laboratório, provavelmente devido a pequenas mudanças no protocolo experimental (detalhes nas instruções fornecidas aos voluntários). Importante salientar que na literatura existem resultados contraditórios na comparação entre atletas e não atletas em tarefas atencionais, provavelmente também por pequenas diferenças nos protocolos experimentais. There is growing interest in scientific information on the role of visual perception and visuospatial attention in sports. We compared Reaction Times (RT) of professional athletes with those of non-athletes in 5 conditions of voluntary visual attention: diffuse, manifest, covert (to the right and to the left of gaze) and divided. Athletes showed shorter mean RT than non-athletes in all experiments. Differences in RT to visual stimuli inside and outside the attentional focus were not significant (p>0,31), except under manifest attention conditions (p=0,0001), but where slightly higher in athletes. These differences were significant in experiments on other populations of interest in our laboratory, probably due to small changes in the experimental protocol (details in the instructions provided to volunteers). It is important to note that the literature presents contradictory results in the comparison between athletes and non-athletes in attentional tasks, again, probably due to small differences in experimental protocol.

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Barros, Beatriz Alves de Castro. "Assimetria interlateral da atenção visuoespacial voluntária." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-28012008-115612/.

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Há evidências que os mecanismos responsáveis pela atenção visuoespacial estão assimetricamente representados nos dois hemisférios cerebrais. A existência de uma diferença interlateral da atenção voluntária foi investigada em uma tarefa de escolha simples e de escolha vai/não-vai. Estímulos pistas centrais unilaterais (indicando lado esquerdo ou direito do espaço) e estímulos pistas centrais bilaterais (indicando ambos os lados do espaço) foram utilizados para direcionar a atenção. Tempos de reação a um alvo quando as pistas eram válidas, inválidas e bilaterais foram avaliados. O efeito atencional (diferença entre o tempo de reação quando a pista era inválida e o tempo de reação quando a pista era válida) foi maior quando a pista indicava o lado direito do que quando indicava o lado esquerdo. Quando a pista ocorria bilateralmente, o tempo de reação foi menor no lado direito do que no lado esquerdo. A atenção voluntária tende a favorecer o lado direito do espaço particularmente quando a discriminação da forma do alvo é requerida. There is evidence that the mechanisms responsible for visuospatial attention are asymmetrically represented in the two cerebral hemispheres. The existence of an interlateral difference of voluntary attention was investigated in a simple choice reaction time task and in a go/no-go choice reaction time task. Unilateral central cues (indicating left side or right side) and bilateral central cue (indicating both sides of space) were used to control attention. Reaction time to a visual target stimulus when the cue was valid, invalid or bilateral was evaluated. The attentional effect (difference between reaction time when the cue was invalid minus when the cue was valid) was larger when the cue indicated the right side than when it indicated the left. When the cue occurred bilaterally, reaction time was faster on the right hemifield. The voluntary attention tends to favor the right side of space particularly when discrimination of the shape of the target stimulus is required.

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Mota, Amanda Manzini. "Orientação da atenção visual na doença de Parkinson e no envelhecimento." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-25102007-134255/.

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Avaliamos a orientação da atenção visual de pacientes com Doença de Parkinson (DP), idosos e jovens saudáveis. Foram feitos cinco experimentos de Tempo de Reação (TR) e de Julgamento de Ordem Temporal (JOT), nos quais se avaliaram a atenção automática e voluntária e a percepção de ordem temporal. Os pacientes com DP apresentaram déficits em relação aos idosos na atenção voluntária, na percepção de ordem temporal e na flexibilidade mental, mas tiveram resultados semelhantes aos idosos na avaliação da atenção automática. A correlação entre os valores do TR e do JOT foi significativa entre os experimentos de TR e JOT, o que evidencia que os déficits dos DP e idosos têm origem num mecanismo em comum: a atenção. We investigated the orienting of visual attention in patients with Parkinson?s disease (PD), healthy elderly and young subjects. Five Reaction Time (RT) and Temporal Order Judgment (TOJ) experiments were performed in order to evaluate automatic and voluntary attention and perception of temporal order. The PD patients exhibited a deficit when compared to the healthy elderly subjects in voluntary attention, perception of temporal order and mental flexibility, but had similar results in the automatic attention task. The correlation between the values obtained in RT and TOJ experiments was significant, which points towards a common mechanism underlying deficits of PD patients and effects of aging: attention.

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Yang, Taoxi [Verfasser], and Ernst [Akademischer Betreuer] Pöppel. "Inhomogeneity of visual space, discontinuity of perceptual time and cultural imprinting as exemplified with experiments on visual attention, aesthetic appreciation and temporal processing / Taoxi Yang ; Betreuer: Ernst Pöppel." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/119811195X/34.

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Sneed, Brian James. "The Use of Viewing Time of Non-erotic Visual Stimuli to Differentiate Between Frequent Pornography Users and Infrequent Users." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/437.

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The purpose of this study was to determine whether a measure of viewing time that uses non-erotic visual stimuli can differentiate between frequent users and infrequent users of pornography. Thirty-six male participants were classified as infrequent pornography users and 37 as frequent users. Participants completed a questionnaire and were asked to rate a variety of images, both male and female of varying ages, on their sexual attractiveness. Individuals were timed as to how long they looked at each image. The groups were then compared based upon their viewing time of several categories. No statistically significant differences were detected. The temporal stability of the measure was also investigated. Researchers found that for the two groups, high correlations were found with juvenile females and adult females, somewhat strong correlations for small male child and pre-juvenile female, and relatively weak correlations for adult males, small female child, juvenile male, and pre-juvenile male. Researchers also attempted to differentiate the two groups based upon their temporal stability. A statistically significant difference between the groups was found with their viewing times of pre-juvenile females; however, the researchers caution the readers about its interpretation. Researchers concluded that perhaps the viewing time measure used in this study was not sufficiently sensitive enough to differentiate on pornography use. They indicated that perhaps viewing time measures utilizing erotic visual stimuli may be more effective in detecting such a difference. The researchers also speculated that there may be differences between pornography users and non pornography users and that pornography may not be the factor responsible for causing callousness towards women, acceptance of rape myths, and a reduction in sexual and marital satisfaction. The researchers suggested that there may be another factor responsible for causing these negative effects and also predisposes an individual to heavy pornography use.

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Bueno, Viviane Freire. "Influência da atenção temporal em tarefas de discriminação visual e auditiva." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/47/47135/tde-19072011-085923/.

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A ocorrência repetida de um estímulo sensorial precedendo o estímulo alvo geralmente reduz o tempo de reação (TR). Este efeito tem sido atribuído à atenção temporal mobilizada pelo estímulo precedente que facilitaria a resposta no momento em que o estímulo alvo fosse esperado. Examinamos a atuação da estimulação precedente em tarefas de TR de discriminação sensorial. Em um primeiro experimento testamos noventa e seis adultos jovens de ambos os sexos. Metade dos participantes realizou uma tarefa de TR que exigia a localização (esquerda ou direita) dos estímulos alvos visuais ou auditivos. A outra metade dos participantes realizou uma tarefa de TR que exigia a identificação da forma, no caso de estímulos visuais, e da seqüência de tons, no caso de estímulos auditivos. O estímulo alvo visual podia ser um círculo ou uma elipse. O estímulo alvo auditivo podia ser uma seqüência ascendente constituída por um tom de 1000 Hz seguido por um tom de 3000 Hz ou uma seqüência descendente formada por um tom de 3000 Hz seguido por um tom de 1000 Hz. A resposta consistiu em pressionar uma tecla com a mão esquerda ou a direita dependendo do estímulo alvo o mais rápido possível. O estímulo alvo podia ser precedido pelo piscar de um retângulo com as dimensões da tela do monitor de vídeo ou por um tom de 300 Hz e 57 dB. A assincronia entre o início dos dois estímulos (AIE) podia ser de 50, 100, 200, 400, 800 ou 1600 ms, em blocos de tentativas separados. Nas tarefas de localização, o estímulo precedente visual produziu efeito facilitador na AIE de 400 ms quando o estímulo alvo era visual. O estímulo precedente auditivo produziu efeito facilitador nas AIE de 50, 100, 200, 400, 800 e de 1600 ms quando o estímulo alvo era visual e nas AIE de 400, 800 e 1600 ms quando o estímulo alvo era auditivo. Nas tarefas de identificação, o estímulo precedente auditivo produziu efeito facilitador nas AIE de 200 e 400 ms quando o estímulo alvo era visual e nas AIE de 400, 800 e 1600 ms quando o estímulo alvo era auditivo. Em um segundo experimento, equilibramos o nível de dificuldade das tarefas de discriminação visual com estimulação precedente auditiva. Doze participantes realizaram uma tarefa de TR que exigia a localização do estímulo (acima e abaixo do ponto de fixação, tanto à esquerda como à direita). Outros doze participantes realizaram uma tarefa de TR que exigia a identificação da forma para a escolha da mão de resposta. Na tarefa de localização, o estímulo precedente auditivo produziu um efeito facilitador que não diferiu entre as AIE. Na tarefa de identificação, o estímulo precedente auditivo produziu efeito facilitador na AIE de 400 ms. A mobilização da atenção temporal e sua atuação ao longo do tempo dependem do tipo de tarefa realizada e da natureza do estímulo precedente e do estímulo alvo. Estímulos auditivos mobilizam mais intensamente a atenção temporal do que estímulos visuais The repeated occurrence of a prime stimulus preceding a target stimulus reduces a reaction time (RT). This effect has been usually attributed to the temporal attention mobilized by the prime stimulus which would facilitate the response at the moment that the target stimulus is expected. We systematically examined the influence of temporal attention on RT in sensory discrimination tasks. In one experiment we tested ninety-six young adults of both sexes. Half of the participants carried out a task which required the identification of the location of appearance of target auditory or visual stimuli (left or right). The other half of the participants carried out a task which required the identification of the shape, in the case of visual stimuli, and tones sequence, in the case of auditory stimuli. The visual target stimulus could be a circle or an ellipse. The auditory target stimulus could be an ascending sequence formed by a 1000 Hz tone followed by a 3000 Hz tone or a descending sequence formed by a 3000 Hz tone followed by a 1000 Hz tone. The response was a key press, which should be performed as fast as possible. The target stimulus could be preceded by the flashing of the border of the screen or by a 57 dB 300 Hz tone. The stimulus onset asynchronies (SOA) could be 50, 100, 200, 400, 800 or 1600 ms, in separated blocks of trials. In the identification tasks location, the visual prime stimulus produced facilitatory effect for SOA of 400 ms when the target stimulus was visual. The auditory prime stimulus produced a facilitatory effect for SOA of 50, 100, 200, 400, 800, and of 1600 ms when the target stimulus was visual and for SOA of 400, 800, and 1600 ms when the target stimulus was auditory. In the tasks of object identification, the auditory prime stimulus produced a facilitatory effect for SOA of 200 and 400 ms when the target stimulus was visual and for SOA of 400, 800 and 1600 ms when the target stimulus was auditory. In another experiment, we balanced the level of difficult of the visual discrimination tasks. We tested only the auditory prime stimulus. Twelve participants carried out a task which required the identification of the location of the target stimulus (upper and lower visual hemifield on left or right of the fixation point). Another twelve participants carried out a task which required the identification of the shape of the target stimulus. In the task of location identification, the auditory prime stimulus produced a facilitatory effect independent of the SOA. In the task of shape identification, the auditory prime stimulus produced a facilitatory effect for SOA of 400 ms. The mobilization of temporal attention and the time course depend on the type of task being performed and the nature of the prime and the target stimulus. Auditory prime stimuli mobilize temporal attention more intensely than visual prime stimulus

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Squella, Sara Agueda Fuenzalida. "Efeito inibidor de um estímulo precedente visual em uma tarefa de tempo de reação simples." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-19102007-155021/.

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Estudos sobre a orientação da atenção que utilizam o procedimento de Posner têm demonstrado dois efeitos: uma facilitação inicial no processamento do estímulo que aparece no lugar para onde dirigiu-se a atenção e subsequentemente um prejuízo no processamento deste estímulo, neste local. Em um trabalho anterior não evidenciamos o efeito facilitador da orientação da atenção em uma tarefa de tempo de reação simples. Levantamos algumas hipóteses para explicar este efeito oposto. Para testarmos tais hipóteses realizamos 6 experimentos. Nos dois primeiros, examinamos em que medida a presença de tentativas de pegada influenciava a expressão do efeito negativo do estímulo precedente. No terceiro examinamos a possibilidade do estímulo precedente ser capaz de reduzir a responsividade. No quarto equalizamos a intensidade efetiva do estímulo alvo nas duas posições em que ele podia ser apresentado (mesma e oposta). No quinto e no sexto avaliamos a evolução temporal do efeito negativo do estímulo precedente, na tentativa de determinar até que ponto ela teria alguma relação com a evolução temporal esperada para um mascaramento anterógrado. O sexto experimento poderia adicionalmente fornecer alguma pista de uma contribuição de uma inibição de retorno, neste caso precoce, para o efeito negativo encontrado. Em todos esses casos a influência atencional do estímulo precedente presumivelmente continuaria a ocorrer, mas seria suplantada pela influência contrária coexistente. Em conjunto, nossos resultados sugerem que o efeito negativo do estímulo precedente em uma tarefa de tempo de reação simples, se deve a uma interferência com o processamento do estímulo alvo, caracterizando uma inibição de natureza sensorial. Studies about attention orienting that use Posner?s procedure have demonstrated two effects: an initial facilitation of responsivit when the target stimulus appears in the same location as the prime stimulus and a subsequent inhibition of this responsvity. In a previous work we could not find the early facilitatory effect of attention orienting in a simple reaction time task. The hypotheses that we raised to explain this unexpected finding were tested in six experiments. In the first two ones, we examined whether the presence of catch trials influenced the expression of the negative effect of the prime stimulus. In the third experiment we examined the possibility that the prime stimulus reduced responsivity. In the fourth experiment we equalized the intensity of the target stimulus in the two locations where it could be presented (same and opposite). In the fifth and in sixth experiments we evaluated the time course of the negative effect of the prime stimulus, as an attempt to verify whether it would be compatible with a forward masking process. The sixth experiment could additionally give some clue about a contribution of inhibition of return, in this case precocious, to the found negative effect. In all these cases the attentional influence of the prime stimulus would presumably continue to occur, but would be supplanted by the contrary negative of this stimulus influence. Overall, our results suggest that the negative effect of the prime stimulus in a simple reaction time task is due to an interference with the processing of the target stimulus, characterizing a kind of sensory inhibition.

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Fiske, Steven William. "Does Crowding Obscure the Presence of Attentional Guidance in Contextual Cueing?" Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4039.

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The contextual cueing effect was initially thought to be the product of memory guiding attention to the target location. However, the steep search slopes obtained in contextual cueing indicate an absence of attentional guidance. We hypothesized that crowding could be obscuring the presence of attentional guidance and investigated this possibility in 2 experiments. Crowding was manipulated by varying the density of items in the local target region in a contextual cueing task. We observed a significant reduction in search slopes between the novel and repeated conditions when crowding was reduced. Enhancing crowding eliminated the contextual cueing effect. These findings suggest that increased crowding at larger set sizes attenuates the memory-based attentional guidance in contextual cueing thereby producing steep search slopes.

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Pinheiro, Gisele Braga. "Contribuição sensorial na facilitação do estímulo precedente." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/42/42137/tde-10012011-133827/.

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A ocorrência de um estímulo auditivo imediatamente antes de um estímulo alvo visual reduz o tempo de reação em dezenas de milisegundos, um efeito atribuído a atenção temporal automática. O presente estudo investigou se este efeito é resultante de uma facilitação de mecanismos sensoriais. Dois experimentos foram realizados. No primeiro, foi realizada uma tarefa de tempo de reação simples por meio da resposta a estímulos alvos visuais com variações em sua detectabilidade. Esperava-se que o tamanho do efeito facilitador pudesse aumentar com o aumento da dificuldade de detecção do alvo. No segundo experimento foi realizada uma tarefa de acurácia. Os dados foram analisados pela teoria de detecção de sinais. Esperava-se que o estímulo precedente possibilitasse o aumento da detectabilidade do alvo e redução do critério de resposta. No primeiro experimento, não houve influência do estímulo precedente no aumento da detectabilidade do alvo. Os resultados do segundo experimento indicaram haver influência do estímulo precedente no aumento da detectabilidade do alvo e redução do critério pra a resposta. Esses resultados reforçam a teoria de que a atenção temporal automática facilita o processamento sensorial. The occurrence of an auditory stimulus immediately before a visual target stimulus shortens reaction time by tens of milliseconds, an effect attributed to automatic temporal expectation. The present study investigated whether this effect results from a facilitation of sensory mechanisms. Two experiments were performed. In the first one the volunteers performed a simple reaction time task. They responded to visual targets which differ in detectability. It was expected that the size of the facilitatory effect would increase with the difficulty of target detection. In the second experiment the volunteers performed an accuracy task. Its data were analyzed on basis of signal detection theory. It was expected that the warning stimulus would increase the detectability of the target and lower the criterion to respond. The results of the first experiment did not indicate any influence of target detectability. The results of the second experiment indicate that both the detectability of the target and the criterion to respond were affected by the warning stimulus. These results provide support to the idea that automatic temporal expectancy facilitates sensory processing.

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Mizzi, Raphaël. "Mécanismes cognitifs et substrat neuronal de la hérarchisation de la saillance et de la progression de l'attention : approche psychophysique." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE2122/document.

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Lorsque le système visuel est confronté à un nouvel environnement, un nombre trop important d’informations lui parvient en même temps. De façon précoce, avant tout mouvement oculaire, l’attention explore automatiquement la scène pour sélectionner les éléments d’intérêt. Des recherches récentes ont montré que cette exploration du champ visuel ne se faisait pas aléatoirement, mais se basait sur la saillance des éléments visuels. La saillance est une caractéristique qui émerge de la comparaison des éléments visuels entre eux, par exemple une fleur jaune dans un jardin de fleurs rouges va être considérée comme plus saillante que son voisinage. En permanence et de façon continue, une hiérarchie des éléments est établie à un niveau préattentif ; ils sont triés du plus au moins saillant, et l’attention se base sur cet organisation pour progresser dans le champ visuel. Les recherches présentées dans ce document avaient pour objectif d’investiguer les mécanismes de ce phénomène : quels sont les mécanismes cognitifs impliqués dans la progression de l’attention sur la base de la hiérarchie de la saillance ? Le présent document regroupe des articles qui cherchent à répondre à cette question grâce à des travaux en Psychologie expérimentale. Par ailleurs, de nombreux travaux de Psychologie, Neurophysiologie et Neuroimagerie se sont penchés sur le substrat neural de l’attention visuelle et ont révélé un ensemble de structures clés qui sous-tendraient les mécanismes responsables des fonctions attentionnelles. Cependant, vis-à-vis de la progression de l’attention sur la base de la saillance, seule une étude récente a pu apporter des indices quant au rôle de certaines voies visuelles. Les recherches présentées ici avaient donc également pour objectif de définir ces voies visuelles et les structures corticales et sous-corticales qui les composent, pour investiguer leurs rôles dans la hiérarchie de la saillance et la progression de l’attention. Le présent document regroupe des travaux qui ont exploré ces aspects par le biais de l’approche Psychophysique et Electroencéphalographique When confronted to a new environment, the visual system faces too much information intake and cannot process it all at once. Before any eye movement, early automatic attention explores the visual scene in order to select relevant items.Recent research revealed that the exploration of the visual scene is not a random process, but is based on the respective saliency of the items in the field. Salience is not a characteristic of an item per se but is emerging as a result of the comparison between an item and its visual neighborhood. For instance, a yellow flower in a garden of red flowers will be considered as more salient than the others in its visual neighborhood. Thus, a hierarchical ordering of the items is continuously established in a preattentive stage, and consists in a sorting of every element from the most to the least salient. Attention, then, relies on this hierarchy to progress in the visual field. The present dissertation had for objective to investigate the cognitive mechanisms involved in this phenomenon: what mechanisms support the salience-based progression of visual attention? Several papers are reported here and explored this question with experimental Psychology.Moreover, numerous works in Psychology, Neurophysiology and Neuroimaging took interest in the neural substrate of visual attention and revealed several key-structures that would subtend the mechanisms involved in attentional functions. However, when it comes to the salience-based progression of attention, only one study could bring cues of the involvement of certain visual pathways in this phenomenon. Another objective of the present dissertation was to define the cortical and sub-cortical structures that constitute those pathways, in order to explore their roles in the salience-base progression of attention. Several papers in the present report are investigating this aspect through Psychophysics and Electroencephalography studies

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Lin, Yi-shin. "Decision making in visual search : a dual-modelling approach to examine the influences of attentional templates in response time distributions." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6168/.

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The remarkable ability of human search inspires computer vision algorithms that have influenced our life. The algorithms often automatically reach an optimal decision upon finishing analysing stimulus information. This is not how human search works. One missing puzzle psychophysical studies have yet to answer is how a search decision is reached. This thesis addressed this question, using descriptive models to examine response time (RT) distributions and cognitive process models to reveal the hidden information. The thesis focused on those search paradigms, guided (Wolfe, 2007a) by an attentional template (Duncan & Humphreys, 1989), because not until recent years, relevant techniques become more accessible to apply the pioneering approach of dual-modelling. The thesis compared RT distributions and cognitive processes when observers were guided by different attentional templates to search for a target. The first search paradigm was to discriminate 2 from 5. Study 2 varied the working memory strengths in templates, and they were represented differently (null, abstract vs. concrete) in Study 3. The findings suggest attentional templates selectively influence different parts of a search decision and RT distributions, depending on how a template is represented, whether il is strengthened or weakened by the conditions, and whether it is concrete or abstract.

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Birem, Merwan. "Localisation et détection de fermeture de boucle basées saillance visuelle : algorithmes et architectures matérielles." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22558/document.

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Dans plusieurs tâches de la robotique, la vision est considérée comme l’élément essentiel avec lequel la perception de l’environnement ou l’interaction avec d’autres utilisateurs peut se réaliser. Néanmoins, les artefacts potentiellement présents dans les images capturées rendent la tâche de reconnaissance et d’interprétation de l’information visuelle extrêmement compliquée. Il est de ce fait, très important d’utiliser des primitives robustes, stables et ayant un taux de répétabilité élevé afin d’obtenir de bonnes performances. Cette thèse porte sur les problèmes de localisation et de détection de fermeture de boucle d’un robot mobile en utilisant la saillance visuelle. Les résultats en termes de précision et d’efficacité des applications de localisation et de détection de fermeture sont évalués et comparés aux résultats obtenus avec des approches de l’état de l’art sur différentes séquences d’images acquises en milieu extérieur. Le principal inconvénient avec les modèles proposés pour l’extraction de zones de saillance est leur complexité de calcul, ce qui conduit à des temps de traitement important. Afin d’obtenir un traitement en temps réel, nous présentons dans ce mémoire l’implémentation du détecteur de régions saillantes sur la plate forme reconfigurable DreamCam In several tasks of robotics, vision is considered to be the essential element by which the perception of the environment or the interaction with other users can be realized. However, the potential artifacts in the captured images make the task of recognition and interpretation of the visual information extremely complicated. It is therefore very important to use robust, stable and high repeatability rate primitives to achieve good performance. This thesis deals with the problems of localization and loop closure detection for a mobile robot using visual saliency. The results in terms of accuracy and efficiency of localization and closure detection applications are evaluated and compared to the results obtained with the approaches provided in literature, both applied on different sequences of images acquired in outdoor environnement. The main drawback with the models proposed for the extraction of salient regions is their computational complexity, which leads to significant processing time. To obtain a real-time processing, we present in this thesis also the implementation of the salient region detector on the reconfigurable platform DreamCam

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Rao, Satyajit 1965. "Visual routines and attention." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/49988.

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Li, Qi. "Interactions between Visual Attention and Visual Working Memory." Kyoto University, 2015. http://hdl.handle.net/2433/199403.

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Kyoto University (京都大学) 0048 新制・課程博士 博士(人間・環境学) 甲第19079号 人博第732号 新制||人||176(附属図書館) 26||人博||732(吉田南総合図書館) 32030 京都大学大学院人間・環境学研究科共生人間学専攻 (主査)教授齋木潤, 教授船橋新太郎, 准教授月浦崇 学位規則第4条第1項該当

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Ramström, Ola. "Visual attention using game theory." Licentiate thesis, KTH, Numerical Analysis and Computer Science, NADA, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-349.

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Bauer, Frank. "Visual Attention and Temporal Binding." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-49507.

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Guest, Duncan. "Visual Attention and Perceptual Categorisation." Thesis, University of Warwick, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490408.

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Process models of categorisation have been developed to account for the interactions between perceptual processes and decisional processes in categorisation. The formalised relation between perceptual and decisional processes described in the extended generalised context model (K Lamberts, 1995, 1998) has been shown to provide a good account of time course data from categorisation tasks as well as other tasks such as perceptual matching and recognition. In a set of four experiments the assumption in the extended generalised context model that visual attention has a negligible influence on perceptual and decisional processes was examined. Experiment 1 and 2 examined whether visual attention could influence perceptual processing and Experiment 3 and 4 examined whether visual attention could influence both perceptual and decisional processes in categorisation. Contrary to previous findings Experiments 1-4 demonstrated that visual attention can have a large influence on perceptual processing in categorisation. Consistent with previous results it was found that visual attention does not influence decisional processes in categorisation and that there are multiple systems of attention controlling decisional and perceptual processes in categorisation. In Experiment 5 and 6, the extended generalised context model was extended for application to visual search tasks. Experiments 5 and ~ examined whether this new model could account for the time course of similarity effects in visual search. The new model provided a good account of the time course of similarity effects and display size effects. The implications of these findings are discussed in relation to the research on perceptual and decisional processes in categorisation and alternative theories of visual search.

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Harpur, Timothy John. "Visual attention in psychopathic criminals." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/31019.

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This study was designed to examine the hypothesis that criminal psychopaths differ from criminal nonpsychopaths in their ability to over-focus attention on certain kinds of stimuli. For the purposes of this study, the concept of over-focussing was operationalized to mean the ability to process stimuli more quickly or efficiently by making use of one or more attentional mechanisms for selecting among locations or stimuli. A second aim of the study was to identify the component processes contributing to this more efficient selection. Five experiments were run to assess several different components of attention contributing to selection of stimuli in a variety of paradigms. Experiments 1 and 2 assessed covert orienting of attention across the visual field using both peripherally presented physical cues and centrally presented symbolic cues to prime locations in visual space. Three dissociable components of attention were assessed in this paradigm. Experiments 3-5 were designed to assess the efficiency of processing a target item in the presence of a distractor item. Four additional dissociable components of selective attention were measured in these three studies. The results supported the hypothesis that psychopaths can over-focus attention, but the groups were differentiated by only one of the component processes measured. In Experiments 1 and 2 endogenous orienting of attention was greater for psychopaths than for nonpsychopaths. In these paradigms endogenous facilitation controlled the allocation of attention to cued locations, and the subsequent speeding of reaction time to targets presented at those locations, when the cue was symbolic or predictive, but not when it involved a physical change of energy at the cued location. This strategic allocation of attention probably resulted from the predictive validity (approximately 68% valid) of the cue in relation to the target. Other component processes failed to differentiate the groups. These included measures of exogenous orienting and inhibition of return in experiments 1 and 2, and measures of interference due to a distracting stimulus, habituation of interference, attenuation of interference due to spatial displacement of the distractor, and negative priming in experiments 3-5. The difference in covert orienting was replicated in experiments 1 and 2 in two groups of criminals who also failed to demonstrate any abnormalities in a variety of other processes involved in attention. It was concluded that psychopaths differ from nonpsychopaths specifically in their strategic allocation of attention in situations of moderate uncertainty, but show no other abnormalities in the component processes that control attention. Arts, Faculty of Psychology, Department of Graduate

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Kohler, Axel. "Motion, attention, and visual awareness." Maastricht : Maastricht : Universitaire Pers Maastricht ; University Library, Universiteit Maastricht [host], 2006. http://arno.unimaas.nl/show.cgi?fid=6485.

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Morris, Tonia Gay. "Analog VLSI visual attention systems." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15010.

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Michel, Rachel Keyes. "Visual perception, search, and attention." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/29580.

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O'Brien, Jennifer L. "Motivation and visual selective attention." Thesis, Bangor University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496101.

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MacFarlane, Hood Bruce. "Development of visual selective attention." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387062.

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GRIER, REBECCA ANNE. "VISUAL ATTENTION AND WEB DESIGN." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1092767744.

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Benwell, Christopher Stephen Yates. "Pseudoneglect and visual attention networks." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/7202/.

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Pseudoneglect represents the tendency for healthy individuals to show a slight but consistent bias in favour of stimuli appearing in the left visual field. The bias is often measured using variants of the line bisection task. An accurate model of the functional architecture of the visuospatial attention system must account for this widely observed phenomenon, as well as for modulation of the direction and magnitude of the bias within individuals by a variety of factors relating to the state of the participant and/or stimulus characteristics. To date, the neural correlates of pseudoneglect remain relatively unmapped. In the current thesis, I employed a combination of psychophysical measurements, electroencephalography (EEG) recording and transcranial direct current stimulation (tDCS) in an attempt to probe the neural generator(s) of pseudoneglect. In particular, I wished to utilise and investigate some of the factors known to modulate the bias (including age, time-on-task and the length of the to-be-bisected line) in order to identify neural processes and activity that are necessary and sufficient for the lateralized bias to arise. Across four experiments utilising a computerized version of a perceptual line bisection task, pseudoneglect was consistently observed at baseline in healthy young participants. However, decreased line length (experiments 1, 2 and 3), time-on-task (experiment 1) and healthy aging (experiment 3) were all found to modulate the bias. Specifically, all three modulations induced a rightward shift in subjective midpoint estimation. Additionally, the line length and time-on-task effects (experiment 1) and the line length and aging effects (experiment 3) were found to have additive relationships. In experiment 2, EEG measurements revealed the line length effect to be reflected in neural activity 100 – 200ms post-stimulus onset over source estimated posterior regions of the right hemisphere (RH: temporo-parietal junction (TPJ)). Long lines induced a hemispheric asymmetry in processing (in favour of the RH) during this period that was absent in short lines. In experiment 4, bi-parietal tDCS (Left Anodal/Right Cathodal) induced a polarity-specific rightward shift in bias, highlighting the crucial role played by parietal cortex in the genesis of pseudoneglect. The opposite polarity (Left Cathodal/Right Anodal) did not induce a change in bias. The combined results from the four experiments of the current thesis provide converging evidence as to the crucial role played by the RH in the genesis of pseudoneglect and in the processing of visual input more generally. The reduction in pseudoneglect with decreased line length, increased time-on-task and healthy aging may be explained by a reduction in RH function, and hence contribution to task processing, induced by each of these modulations. I discuss how behavioural and neuroimaging studies of pseudoneglect (and its various modulators) can provide empirical data upon which accurate formal models of visuospatial attention networks may be based and further tested.

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Driver, Jonathon S. "Selective attention." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236243.

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Guo, Dalu. "Attention Networks in Visual Question Answering and Visual Dialog." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25079.

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Attention is a substantial mechanism for human to process massive data. It omits the trivial parts and focuses on the important ones. For example, we only need to remember the keywords in a long sentence and the principal objects in an image for rebuilding the sources. Therefore, it is crucial to building an attention network for artificial intelligence to solve the problem as human. This mechanism has been fully explored in the text-based tasks, such as language translation, reading comprehension, and sentimental analysis, as well as the visual-based tasks, such as image recognition, object detection, and action recognition. In this work, we explore the attention mechanism in the multi-modal tasks, which involve the inputs of both text and image, i.e. visual question answering and visual dialog. It involves three vital components in both tasks, the input question (with history for visual dialog), the given image, and the generated answers. Therefore, three kinds of relationships should be investigated step by step to solve the problem. We first build the attention between words and objects for generating the representation of them, followed by the relationship between the representation and the answers if the general word embedding does not work properly, and the relationship between the representation and the attributes of answers comes last for few-shot learning. First, the bilinear graph networks revisit the relationship between the words from question and objects for image in the visual question answering task from a graph perspective. The classical bilinear attention networks build a bilinear attention map to extract the joint representation of words and objects but lack fully exploring the relationship between words for complex reasoning. In contrast, our networks model the context of the joint embeddings of words and objects. Two kinds of graphs are investigated, namely image-graph and question-graph. The image-graph transfers features of the detected objects to their related query words, enabling the output nodes to have both semantic and factual information. The question-graph exchanges information between these output nodes from image-graph to amplify the implicit yet important relationship between objects. These two kinds of graphs cooperate with each other, and thus our resulting model can model the relationship and dependency between objects, which leads to the realization of multi-step reasoning. Then, our novel image-question-answer synergistic network values the role of the answer for precise visual dialog. We extend the traditional one-stage solution to a two-stage solution. In the first stage, candidate answers are coarsely scored according to their relevance to the image and question pair. Afterward, in the second stage, answers with high probability of being correct are re-ranked by synergizing with image and question. Finally, we propose to learn the representations of attributes from the answers with enough data, which are later composed to constrain the learning of the few-shot ones. We generate the few-shot dataset of VQA with a variety of answers and extract their attributes without any human effort. With this dataset, we build our attribute network to disentangle the attributes by learning their features from parts of the image instead of the whole one.

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Cissell, Gayla. "An Investigation of Visual Attention in Attention-Deficit Hyperactivity Disorder." TopSCHOLAR®, 1994. http://digitalcommons.wku.edu/theses/935.

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What is known as Attention-deficit Hyperactivity Disorder (ADHD) today has been known by other titles in the past such as minimal brain dysfunction and Hyperkinetic Reaction of Childhood. These label changes represented the change in knowledge and understanding of the disorder over time. Today, it is thought that a main component to the disorder is an attention deficit. The problem is that of yet, the cause of this deficit has not been identified. In an attempt to further understand this disorder, visual attention studies are being conducted. Following this lead, the Visual Attention Analyzer was used to investigate a link between ADHD and visual attention. As the UFOV™ had never been used as a measure of visual attention in children, two studies were performed. The first study was to establish the UFOV™ Visual Attention Analyzer as a reliable measure of visual attention in children. It was found using the test-retest method that the UFOV™ is a test of moderate reliability for six and seven year olds. As there was little variability in the eight to fifteen year olds' performance, the Pearson correlation coefficient was truncated, producing a low reliability score. When the discrepancy in pre and post composite scores were examined, in this regard, it was found that the UFOV™ was actually a more reliable measure for the older children than the younger children. With the question concerning the reliability of the UFOV™ as a measure of visual attention in children answered, the second study addressed primarily whether there was a difference between children with Attention-Deficit Hyperactivity Disorder (ADHD) characteristics and normal childrens' performance of the UFOV™ tasks. Based on the most stringent definition of ADHD used in the study, the UFOV™ did not discriminate between the seven year old children with ADHD characteristics and normal children. It did discriminate between the eight through twelve year old children with ADHD characteristics and normal children.

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Lundqvist, Daniel. "The face of wrath : how facial attention captures visual attention /." Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-556-5.

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Bruce, Neil. "Evolutionary Design for Computational Visual Attention." Thesis, University of Waterloo, 2003. http://hdl.handle.net/10012/900.

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A new framework for simulating the visual attention system in primates is introduced. The proposed architecture is an abstraction of existing approaches influenced by the work of Koch and Ullman, and Tompa. Each stage of the attentional hierarchy is chosen with consideration for both psychophysics and mathematical optimality. A set of attentional operators are derived that act on basic image channels of intensity, hue and orientation to produce maps representing perceptual importance of each image pixel. The development of such operators is realized within the context of a genetic optimization. The model includes the notion of an information domain where feature maps are transformed to a domain that more closely corresponds to the human visual system. A careful analysis of various issues including feature extraction, density estimation and data fusion is presented within the context of the visual attention problem.

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Dissertations / Theses on the topic 'Visual attention in time'

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