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If researchers are able to derive usability simply by analysing gaze data it provides a quick, objective and potentially automatic way of measuring the usability of an interface. In order to do that it is essential to know which traits of the gaze data that have an impact on usability. This paper investigates these traits by analysing different eye tracking metrics in the data. The goal is to see which of these metrics have a general correlation with usability. Previous research provides a clue about which metrics are useful when analysing usability. However, much of the research is based on subjective analysis or lacks in general applicability. This research provides an objective analysis that is independent of characteristics of the interface. A user study is done on 20 participants. They complete tasks on nine different ecommerce websites while their eye movements are recorded. Correlation is measured between usability and eye tracking metrics in order to investigate which metrics that are sensitive to changes in usability. The results show that fixational backtracks and number of fixations have the strongest correlation with usability. Previous research did suggest that both of these eye tracking metrics have an impact on usability. / Om det är möjligt för forskare att härleda användbarhet endast genom att analysera ögondata så tillhandahålls ett snabbt, objektivt och potentiellt automatiserat sätt att mäta användbarheten hos ett gränssnitt. För att göra detta är det avgörande att veta vilka karakteristiska drag i ögondatan som påverkar användbarheten. Denna rapport utforskar dessa drag genom att analysera olika mått i ögondatan. Målet är att se vilka av dessa mått som uppvisar en generell korrelation med användbarhet. Tidigare forskning förser oss med ledtrådar om vilka mått som är lämpliga att analysera när användbarhet ska mätas. Dock så är mycket av denna forskning baserad på subjektiv analys eller saknar generell tillämpbarhet. Denna rapport tillhandahåller en objektiv analys som är oberoende av karakteristiken hos gränssnittet. En användarstudie utförs på 20 deltagare. De utför uppgifter på nio olika webbsidor för e-handel medan deras ögonrörelser spelas in. Korrelation mäts mellan användbarhet och mått i ögondatan för att undersöka vilka mått som är känsliga för förändringar i användbarhet. Resultatet visar att tillbakabildande sackader och antal fixeringar har starkast korrelation med användbarhet. Tidigare forskning visade att båda dessa mått påverkades av användbarheten.

A busca visual é uma habilidade crítica para várias tarefas da vida diária e pode estar prejudicada em pacientes com deficiência visual. O objetivo deste estudo foi comparar a busca visual exploratória entre pacientes com glaucoma primário de ângulo aberto (GPAA) e controles saudáveis, avaliando a correlação espacial entre áreas com perdas localizadas na busca visual exploratória e os defeitos perimétricos, em pacientes com GPAA e com visão normal. Cinquenta e sete indivíduos com visão normal (acuidade visual corrigida melhor que 0.2 logMAR) diagnosticados (grupo GPAA, n = 29) ou não (grupo CONTROL, n = 28) com GPAA, realizaram um exame oftalmológico completo, incluindo perimetria visual (Humphrey -Fast 24.2) e uma tarefa exploratória de busca visual baseada em uma tela com dígitos. Um software personalizado quantificou o (s) tempo (s) gasto (s) até o encontro do número \"4\" em uma matriz aleatória de dígitos distribuídos em cinco áreas, em nove telas sequenciais do programa. Cinco áreas da tela de busca visual foram espacialmente correlacionadas com cinco setores do mapa total deviation (TD) da perimetria visual, após ajustes de ângulo e distância. A análise de covariância (ANCOVA) e testes de correlação foram utilizados para correlacionar parâmetros perimétricos e da busca visual exploratória, por meio de avaliação do tempo individual (gasto para encontrar cada dígito) e tempo total (gasto para completar a tarefa). Os pacientes com GPAA apresentaram pior sensibilidade perimétrica (MD) e de busca visual exploratória do que os controles (MD: -8,02 ± 7,88 dB vs -1,43 ± 1,50 dB; p <0,0001 e tempo total: 106,42 ± 59,64 s vs 52,75 ± 19,07 s; p < 0.0001). A sensibilidade do MD de ambos os grupos correlacionou-se significativamente com o tempo total (GPAA: r = -0.45; p = 0,01 e CONTROL: r = 0,37; p = 0,049). Os testes de ANCOVA mostraram uma correlação significativa entre a busca visual exploratória (tempo individual) e a acuidade visual (P = 0,006) e o diagnóstico de glaucoma (p = 0,005). A sensibilidade média das áreas perimétricas periféricas do grupo GPAA mostrou correlação significativa com o tempo de busca individual nas áreas espaciais correspondentes, exceto na área periférica temporal superior (r = -0,35, p = 0,06). Os controles não mostraram correlação significativa para nenhuma dessas áreas perimétricas, exceto a área periférica temporal superior (r = 0,43, p = 0,02). Com base em nossos resultados, regiões com pior desempenho na busca visual exploratória puderam ser correlacionadas às perdas periféricas localizadas dos pacientes com GPAA. Uma vez que foram estudados pacientes com acuidade visual normal, estes achados destacam a importância do uso de ferramentas de busca visual na avaliação do impacto das perdas perimétricas periféricas em atividades diárias de pacientes com glaucoma. / Visual search is a critical skill for several daily tasks and may be declined in patients with impaired vision. The objectives of this study were to compare the exploratory visual search performance (EVSP) between patients with primary open-angle glaucoma (POAG) and healthy controls, and evaluate the spatial correlation between localized decreases in the EVSP and areas of visual field (VF) loss in normally-sighted patients POAG. Fifty-seven normal vision subjects (best corrected visual acuity better than 0.2 logMAR) diagnosed (POAG group; n= 29) or not (CONTROL group; n= 28) with POAG yielded a complete comprehensive ophthalmological examination, including Humphrey VF tests (SITA-Fast 24.2), and an exploratory visual search digit-based task. A custom software quantified the time (s) spent until patients found the number \"4\" on a random array of digits distributed in five areas on nine sequential screens. Each area was spatially matched with five sectors of the total deviation map from VF, after angle and distance adjustments. Covariance (ANCOVA) and correlation tests were used for correlating VF parameters and EVSP, evaluated through individual time (spent for finding each digit) and total time (spent for completing the task). POAG patients presented worse VF mean deviation (MD) sensitivity and EVSP than controls (MD: -8.02±7.88 dB vs -1.43±1.50 dB; p<0.0001, and total time: 106.42±59.64 s vs 52.75±19.07 s; p<0.0001). MD sensitivity of both groups significantly correlated with total time (POAG: r = -0.45; p = 0.01 and CONTROL: r = 0.37; p = 0.049). ANCOVA tests showed a significant correlation between EVSP (individual time) and both visual acuity (p = 0.006) and glaucoma diagnosis (p = 0.005). The mean sensitivity of the peripheral VF areas of the POAG group showed significant correlation with the individual search time in the corresponding spatial areas, except in the peripheral temporal superior area (r = -0.35, p =0.06). Controls did not show a significant correlation for any of those VF areas, except the peripheral temporal superior area (r =0.43, p =0.02). Based on our results, worse EVSP can be attributable to localized losses in the peripheral VF areas in patients with POAG. Since only normally sighted patients were studied, these findings highlight the importance of using visual search tools to evaluate the impact of peripheral VF loss in daily activities of glaucoma patients, such as driving.

A busca visual é uma habilidade crítica para várias tarefas da vida diária e pode estar prejudicada em pacientes com deficiência visual. O objetivo deste estudo foi comparar a busca visual exploratória entre pacientes com glaucoma primário de ângulo aberto (GPAA) e controles saudáveis, avaliando a correlação espacial entre áreas com perdas localizadas na busca visual exploratória e os defeitos perimétricos, em pacientes com GPAA e com visão normal. Cinquenta e sete indivíduos com visão normal (acuidade visual corrigida melhor que 0.2 logMAR) diagnosticados (grupo GPAA, n = 29) ou não (grupo CONTROL, n = 28) com GPAA, realizaram um exame oftalmológico completo, incluindo perimetria visual (Humphrey -Fast 24.2) e uma tarefa exploratória de busca visual baseada em uma tela com dígitos. Um software personalizado quantificou o (s) tempo (s) gasto (s) até o encontro do número \"4\" em uma matriz aleatória de dígitos distribuídos em cinco áreas, em nove telas sequenciais do programa. Cinco áreas da tela de busca visual foram espacialmente correlacionadas com cinco setores do mapa total deviation (TD) da perimetria visual, após ajustes de ângulo e distância. A análise de covariância (ANCOVA) e testes de correlação foram utilizados para correlacionar parâmetros perimétricos e da busca visual exploratória, por meio de avaliação do tempo individual (gasto para encontrar cada dígito) e tempo total (gasto para completar a tarefa). Os pacientes com GPAA apresentaram pior sensibilidade perimétrica (MD) e de busca visual exploratória do que os controles (MD: -8,02 ± 7,88 dB vs -1,43 ± 1,50 dB; p <0,0001 e tempo total: 106,42 ± 59,64 s vs 52,75 ± 19,07 s; p < 0.0001). A sensibilidade do MD de ambos os grupos correlacionou-se significativamente com o tempo total (GPAA: r = -0.45; p = 0,01 e CONTROL: r = 0,37; p = 0,049). Os testes de ANCOVA mostraram uma correlação significativa entre a busca visual exploratória (tempo individual) e a acuidade visual (P = 0,006) e o diagnóstico de glaucoma (p = 0,005). A sensibilidade média das áreas perimétricas periféricas do grupo GPAA mostrou correlação significativa com o tempo de busca individual nas áreas espaciais correspondentes, exceto na área periférica temporal superior (r = -0,35, p = 0,06). Os controles não mostraram correlação significativa para nenhuma dessas áreas perimétricas, exceto a área periférica temporal superior (r = 0,43, p = 0,02). Com base em nossos resultados, regiões com pior desempenho na busca visual exploratória puderam ser correlacionadas às perdas periféricas localizadas dos pacientes com GPAA. Uma vez que foram estudados pacientes com acuidade visual normal, estes achados destacam a importância do uso de ferramentas de busca visual na avaliação do impacto das perdas perimétricas periféricas em atividades diárias de pacientes com glaucoma. / Visual search is a critical skill for several daily tasks and may be declined in patients with impaired vision. The objectives of this study were to compare the exploratory visual search performance (EVSP) between patients with primary open-angle glaucoma (POAG) and healthy controls, and evaluate the spatial correlation between localized decreases in the EVSP and areas of visual field (VF) loss in normally-sighted patients POAG. Fifty-seven normal vision subjects (best corrected visual acuity better than 0.2 logMAR) diagnosed (POAG group; n= 29) or not (CONTROL group; n= 28) with POAG yielded a complete comprehensive ophthalmological examination, including Humphrey VF tests (SITA-Fast 24.2), and an exploratory visual search digit-based task. A custom software quantified the time (s) spent until patients found the number \"4\" on a random array of digits distributed in five areas on nine sequential screens. Each area was spatially matched with five sectors of the total deviation map from VF, after angle and distance adjustments. Covariance (ANCOVA) and correlation tests were used for correlating VF parameters and EVSP, evaluated through individual time (spent for finding each digit) and total time (spent for completing the task). POAG patients presented worse VF mean deviation (MD) sensitivity and EVSP than controls (MD: -8.02±7.88 dB vs -1.43±1.50 dB; p<0.0001, and total time: 106.42±59.64 s vs 52.75±19.07 s; p<0.0001). MD sensitivity of both groups significantly correlated with total time (POAG: r = -0.45; p = 0.01 and CONTROL: r = 0.37; p = 0.049). ANCOVA tests showed a significant correlation between EVSP (individual time) and both visual acuity (p = 0.006) and glaucoma diagnosis (p = 0.005). The mean sensitivity of the peripheral VF areas of the POAG group showed significant correlation with the individual search time in the corresponding spatial areas, except in the peripheral temporal superior area (r = -0.35, p =0.06). Controls did not show a significant correlation for any of those VF areas, except the peripheral temporal superior area (r =0.43, p =0.02). Based on our results, worse EVSP can be attributable to localized losses in the peripheral VF areas in patients with POAG. Since only normally sighted patients were studied, these findings highlight the importance of using visual search tools to evaluate the impact of peripheral VF loss in daily activities of glaucoma patients, such as driving.

作者檢視視覺注意力研究發現：對於哪些向度刺激能夠攫取注意力這項爭議，至今尚未圓滿解決。針對這項議題，認知心理家提出三種不同假設：一致性假設主張必須符合個體注意力控制狀態的刺激才能產生攫取效果；差異顯著性假設認為，不論干擾刺激屬於何種注意力控制狀態，只要該刺激之特徵差異達到顯著，即能吸引注意力；而物件檔案假設則認為，涉及新開物件檔案動作的刺激，比涉及修改原有物件檔案內容的刺激，更傾向於展現注意力攫取效果。 本研究結合雙眼像差技術與非突現刺激技術，設計出具有深度與大小變化的逼近刺激。並且利用逼近刺激進行四項實驗，試圖解決上述三種假設間的爭議：實驗一證實，逼近刺激確實具有攫取注意力的效果。實驗二發現突現刺激與逼近刺激兩者會互相干擾。實驗三結果顯示，比背景亮的刺激較傾向於吸引注意力。實驗四則發現：在搜尋亮度獨特刺激的作業中，逼近干擾刺激不會造成影響；但在搜尋逼近刺激的作業中，亮度獨特刺激則會產生干擾。另外，實驗五包括兩個子實驗，主要在探討逼近刺激注意力攫取效果的媒介，結果顯示：深度變化對逼近刺激的注意力攫取效果具有重要貢獻，但也必須在不違反大小變化條件的前提下，逼近刺激才能展現注意力攫取效果。 整合本研究前四項實驗可知：實驗一、三的結果並不支持物件檔案假設。在探討逼近與突現刺激干擾情形的實驗二中，一致性假設獲得合於預測的結果；但在操弄亮度與逼近刺激的實驗四中，卻得不到支持證據。至於顯著性假設，除了實驗二所得結果外，普遍都可獲得支持。然而，顯著性假設仍有修正的必要。作者在文中也提出了顯著性假設的初步修正，以及未來相關研究可能的發展方向。

Attention is one of the most impaired cognitive functions in schizophrenia; however, the precise mechanisms underlying schizophrenia-related attention impairment are unclear. Progress in identifying these mechanisms has been hampered by using methods that are not designed to isolate specific cognitive processes. The purpose of the present dissertation was to investigate visual attention among patients with schizophrenia using the visual search paradigm — the dominant paradigm for studying attention in the cognitive sciences. Moreover, the current study used eye-tracking methodology to more finely examine the mechanisms underlying impaired visual search in this clinical population. This dissertation had three main objectives: (1) to investigate whether patients with schizophrenia have smaller and/or less dynamic visual spans, (2) to examine whether certain mechanisms guiding the visual selection of objects are impaired in schizophrenia, and (3) to determine the contribution of visual search performance to substitution test performance. Results indicated that patients’ visual spans are both smaller and less dynamic compared to healthy controls. On the other hand, selectivity for more informative distractors is intact in schizophrenia; however, impaired motion perception results in impaired target discrimination in the context of intact target selection. Results also indicated that visual search performance is a primary determinant of substitution test performance. Collectively, these data demonstrate, on one hand, an impairment among patients with schizophrenia in the distribution and flexible modulation of visual attention and, on the other hand, intact visual selective attention in the presence of strong bottom-up cues. The current data also demonstrate the important contribution of visual attention to a highly sensitive neuropsychological test and, by inference, to patients’ cognitive and real-world functioning.

Attention is one of the most impaired cognitive functions in schizophrenia; however, the precise mechanisms underlying schizophrenia-related attention impairment are unclear. Progress in identifying these mechanisms has been hampered by using methods that are not designed to isolate specific cognitive processes. The purpose of the present dissertation was to investigate visual attention among patients with schizophrenia using the visual search paradigm — the dominant paradigm for studying attention in the cognitive sciences. Moreover, the current study used eye-tracking methodology to more finely examine the mechanisms underlying impaired visual search in this clinical population. This dissertation had three main objectives: (1) to investigate whether patients with schizophrenia have smaller and/or less dynamic visual spans, (2) to examine whether certain mechanisms guiding the visual selection of objects are impaired in schizophrenia, and (3) to determine the contribution of visual search performance to substitution test performance. Results indicated that patients’ visual spans are both smaller and less dynamic compared to healthy controls. On the other hand, selectivity for more informative distractors is intact in schizophrenia; however, impaired motion perception results in impaired target discrimination in the context of intact target selection. Results also indicated that visual search performance is a primary determinant of substitution test performance. Collectively, these data demonstrate, on one hand, an impairment among patients with schizophrenia in the distribution and flexible modulation of visual attention and, on the other hand, intact visual selective attention in the presence of strong bottom-up cues. The current data also demonstrate the important contribution of visual attention to a highly sensitive neuropsychological test and, by inference, to patients’ cognitive and real-world functioning.

Objective: The goal of this research was to determine whether alternate-line shading (zebra-striping) of grid-based displays affects the strategy (i.e., “visual flow”) and efficiency of serial search. Background: Grids, matrices, and tables are commonly used to organize information. A number of design techniques and psychological principles are relevant to how viewers’ eyes can be guided through such visual works. One common technique for grids, “zebra-striping,” is intended to guide eyes through the design, or “create visual flow” by alternating shaded and unshaded rows or columns. Method: 13 participants completed a visual serial search task. The target was embedded in a grid that had 1) no shading, 2) shading of alternating rows, or 3) shading of alternating columns. Response times and error rates were analyzed to determine search strategy and efficiency. Results: Our analysis found evidence supporting a weak effect of shading on search strategy. The direction of shading had an impact on which parts of the grid were responded to most rapidly. However, a left-to-right reading bias and middle-to-outside edge effect were also found. Overall performance was reliably better when the grid had no shading. Exploratory analyses suggest individual differences may be a factor. Conclusion: Shading seems to create visual flow that is relatively weak compared to search strategies related to the edge effect or left-to-right reading biases. In general, however, the presence of any type of shading reduced search performance. Application: Designers creating a grid-based display should not automatically assume that shading will change viewers search strategies. Furthermore, although strategic shading may be useful for tasks other than that studied here, our current data indicate that shading can actually be detrimental to visual search for complex (i.e., conjunctive) targets.

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