Neill(1977) 發現 Stroop 色字干擾作業中前一嘗試 (S1) 的干擾字和 後一嘗試 (S2) 的顏色反應相同時，會對後一嘗試的正確反應形成干擾項 －抑制效果。 本研究以 Neill(1977) 的連續嘗試叫色作業，探討 S2 刺 激類型與 S1 反應至 S2 刺激呈現時距 (RSI) 對干擾項－抑制效果的影 響，並說明簡單抑制論 Neill (1977) 、反應抑制論 Tipper(1985) 及編 碼調適論 Lowe(1985) 的適切性。實驗一探討不同 S2 刺激類型產生的影 響，結果合諧字並沒有任何抑制或促進的效果，符號非字和不合諧字得到 干擾項－抑制效果，皆符合簡單抑制論的預測，反應抑制論也能以策略的 因素來解釋實驗一的結果，而編碼調適論不易解釋合諧字的結果。實驗二 探討色條在不同 RSI 產生效果的變化情形，發現色條在短 RSI 產生很少 的促進影響， 在 RSI 較長的情境中色條皆產生干擾項－抑制效果，較為 支持簡單抑制論的假設，反應抑論和編碼調適論則無法解釋色條在長 RSI 產生的干擾項－抑制效果。因此在連續嘗試的 Stroop 叫色作業中， S2 刺激類型及 RSI 對干擾項－抑制效果產生的影響， 簡單抑制論能直接預 測與解釋， 反應抑制論及編碼調適論對色條在長 RSI 的干擾項－抑制效 果則不易解釋。

Lorsque nous pensons à nous-mêmes, à toutes les caractéristiques physiques ou psychologiques qui nous définissent, à tous les objets que nous possédons, nous avons limpression quils ont un statut bien particulier dans notre esprit, quils sont spéciaux pour nous. Notre propre visage est certainement parmi lune des plus uniques et distinctives de toutes ces informations autoréférentielles. Dans ce travail, nous nous sommes penchés sur les spécificités du traitement visuel du propre visage. Dans un premier chapitre théorique, nous avons questionné la possibilité dutiliser le traitement du propre visage comme un indice de conscience de soi (voir Chapitre 1). Ensuite, nous avons passé en revue les différentes études existantes qui concernaient la spécificité du propre visage ou dautres informations autoréférentielles (voir Chapitre 2). Suite à cette revue de la littérature, il est apparu que lintuition selon laquelle notre propre visage est un stimulus spécial navait pas pu être confirmée unanimement par les études qui nous précédaient. Ce travail ambitionnait donc dévaluer empiriquement dans quelle mesure notre propre visage est traité par le système cognitif de façon différente des autres visages que nous rencontrons. Nous avons tenté de répondre à cette question selon trois angles différents. Tout dabord, nous nous sommes intéressés à la précision de la représentation de notre propre visage en mémoire. Pour cela, nous avons utilisé dans notre première étude une méthode psychophysique permettant de déterminer dans quelle mesure nous sommes capables de détecter des modifications fines apportées à des photographies de notre propre visage (voir Chapitre 4). Ensuite, nous avons examiné si la reconnaissance de notre propre visage, mais aussi celle de notre propre corps, sont sous-tendues par des zones cérébrales spécifiques. A cette fin, au cours dune seconde étude, nous avons utilisé limagerie par résonance magnétique fonctionnelle (IRMf, voir Chapitre 5). Enfin, nous avons testé si le propre visage est particulièrement apte à capturer ou à retenir notre attention lorsquil est présenté de façon inopportune alors que nous sommes occupés à réaliser une tâche sans rapport (voir Chapitres 6, 7 et 8). Pour ce faire, nous avons eu recours, dans une série de trois études, à différents paradigmes attentionnels : un paradigme de jugement de parité, un paradigme de cécité attentionnelle, et un paradigme de recherche visuel lors duquel nous avons procédé à lenregistrement des mouvements oculaires des participants. Tout au long de ce travail, nous avons adopté une approche visant à différencier les effets dautoréférence de simples effets de familiarité. Pour ce faire, dans toutes nos études, nous avons comparé les réponses obtenues lors de la présentation du propre visage du participant à celles obtenues lors de la présentation du visage dune personne hautement familière pour le participant (un ami ou un collègue du même groupe dâge et du même sexe). Par ailleurs, dans les études attentionnelles, les réponses subséquentes à la présentation de ces deux visages familiers étaient également comparées à celles obtenues suite à lapparition de visages de personnes inconnues. En somme, si les performances obtenues sur le propre visage et le visage très familier différaient, nous pourrions penser que ces différences sont dues à laspect autoréférentiel du propre visage. Par contre, si les performances ne différaient pas entre le propre visage et lautre visage très familier mais que ces deux visages se distinguaient des visages inconnus, nous pourrions supposer que nous sommes face à de simples effets de familiarité. La première étude psychophysique a montré que la représentation que nous avons en mémoire de notre propre visage est très précise. Cette précision est seulement limitée par les capacités de discrimination perceptive de notre système visuel. Cependant, il en était de même pour le visage dune autre personne hautement familière. De ce point de vue, il ne semble donc pas que notre propre visage soit spécial. Néanmoins, il semblerait que cette représentation soit sous-tendue par des substrats cérébraux spécifiques, comme indiqué par notre seconde étude en IRMf. Cette étude a aussi montré que notre propre corps serait également traité par des régions cérébrales spécifiques. De plus, certaines régions seraient dédiées au traitement abstrait de notre propre apparence physique puisquelles étaient impliquées indépendamment du type de matériel présenté (visage ou corps). Enfin, nous avons montré, grâce aux trois études attentionnelles, que le propre visage nest pas un distracteur exceptionnel par rapport à dautres visages familiers. En effet, le propre visage ne semble pas capturer lattention de façon automatique. Il semblerait que le propre visage bénéficie simplement dune allocation de lattention préférentielle par rapport à des visages inconnus. En dautres termes, lallocation de lattention au propre visage est sujette à diverses contraintes (par exemple sa localisation spatiale) et il semblerait que lattention soit nécessaire pour identifier le propre visage en tant que tel. Cet ensemble de résultats est discuté dans un dernier chapitre (voir Chapitre 9) où nous tentons de mettre les données provenant des trois perspectives différentes (représentation en mémoire, substrats cérébraux et propriétés attentionnelles relatifs au propre visage) en rapport. De plus, la possibilité dutiliser le propre visage comme outil détude de la conscience de soi ou de différents processus cognitifs (reconnaissance ou attention visuelle) est brièvement passée en revue.<br> <br> When we think about ourselves, about the traits that define us, about the physical characteristics or the objects that we own, we have the intuition that they have a special status in our mind. We deeply feel that they are different from everything else in the world. This thesis concerned the specificity of a highly distinctive self-referential stimulus: the self-face. In the present thesis, we have conducted five studies examining whether the self-face is processed in a special way by comparison with other faces. We have put three main questions: (1) how accurate is the representation of the self-face in memory?; (2) is this representation subtended by specific neural correlates?; and (3) does the self-face have special abilities to attract and/or to hold attention? First, we showed that the perceptual representation in memory of the self-face is similar to that of other familiar faces as regard with its precision. Second, we demonstrated that although ones own face perceptual representation is not really special, the visual processing of the self-face is subtended by specific neural correlates. Apparently, the self-body is also processed via specialised pathways in the brain. In addition, some regions seem devoted to the abstract processing of ones own physical appearance independently of the material presented. Third, we showed that ones own face is not a particularly potent distractor by comparison with other familiar faces. It does not seem able to capture attention but rather benefits from a preferential allocation of attention by comparison with unfamiliar faces. In other words, its attentional processing is subject to various constraints (e.g. spatial localisation, available attentional resources) and attention seems necessary to process self-referential parts of a face. We discussed the idea that the presentation of the self-face can constitute a way to enhance chances of eliciting responses in non-communicative patients but that it is not the best way to study self-consciousness in normal adults when using only behavioural methods. In addition, because of its unique characteristics, the self-face can represent a useful tool of investigation of visual recognition and visual attention.

Regular use of illegal drugs is suspected to cause cognitive impairments. Two substances have received heightened attention: 3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy’) and δ-9-tetrahydrocannabinol (THC or ‘cannabis’). Preclinical evidence, as well as human studies examining regular ecstasy consumers, indicated that ecstasy use may have negative effects on learning, verbal memory and complex attentional functions. Cannabis has also been linked to symptoms of inattention and deficits in learning and memory. Most of the published studies in this field of research recruited participants by means of newspaper advertisements or by using word-of-mouth strategies. Because participants were usually aware that their drug use was critical to the research design, this awareness may have caused selection bias or created expectation effects. Focussing on attention and memory, this study aimed to assess cognitive functioning in a community-based representative sample that was derived from a large-scale epidemiological study. Available data concerning drug use history allowed sampling of subjects with varying degrees of lifetime drug experiences. Cognitive functioning was examined in 284 young participants, between 22 and 34 years. In general, their lifetime drug experience was moderate. Participants completed a neuropsychological test battery, including measures for verbal learning, memory and various attentional functions. Linear regression analysis was performed to investigate the relationship between cognitive functioning and lifetime experience of drug use. Ecstasy and cannabis use were significantly related to poorer episodic memory function in a dose-related manner. For attentional measures, decrements of small effect sizes were found. Error measures in tonic and phasic alertness tasks, selective attention task and vigilance showed small but significant effects, suggesting a stronger tendency to experience lapses of attention. No indication for differences in reaction time was found. The results are consistent with decrements of memory and attentional performance described in previous studies. These effects are relatively small; however, it must be kept in mind that this study focussed on assessing young adults with moderate drug use from a population-based study.

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.

In the human visual system, one of the most prominent functions of the extensive feedback from the higher brain areas within and outside of the visual cortex is attentional modulation. The feedback helps the brain to concentrate its resources on visual features that are relevant for recognition, i. e. it iteratively selects certain aspects of the visual scene for refined processing by the lower areas until the inference process in the higher areas converges to a single hypothesis about this scene. In order to minimize a number of required selection-refinement iterations, one has to find a short sequence of maximally informative portions of the visual input. Since the feedback is not static, the selection process is adapted to a scene that should be recognized. To find a scene-specific subset of informative features, the adaptive selection process on every iteration utilizes results of previous processing in order to reduce the remaining uncertainty about the visual scene. This phenomenon inspired us to develop a computational algorithm solving a visual classification task that would incorporate such principle, adaptive feature selection. It is especially interesting because usually feature selection methods are not adaptive as they define a unique set of informative features for a task and use them for classifying all objects. However, an adaptive algorithm selects features that are the most informative for the particular input. Thus, the selection process should be driven by statistics of the environment concerning the current task and the object to be classified. Applied to a classification task, our adaptive feature selection algorithm favors features that maximally reduce the current class uncertainty, which is iteratively updated with values of the previously selected features that are observed on the testing sample. In information-theoretical terms, the selection criterion is the mutual information of a class variable and a feature-candidate conditioned on the already selected features, which take values observed on the current testing sample. Then, the main question investigated in this thesis is whether the proposed adaptive way of selecting features is advantageous over the conventional feature selection and in which situations. Further, we studied whether the proposed adaptive information-theoretical selection scheme, which is a computationally complex algorithm, is utilized by humans while they perform a visual classification task. For this, we constructed a psychophysical experiment where people had to select image parts that as they think are relevant for classification of these images. We present the analysis of behavioral data where we investigate whether human strategies of task-dependent selective attention can be explained by a simple ranker based on the mutual information, a more complex feature selection algorithm based on the conventional static mutual information and the proposed here adaptive feature selector that mimics a mechanism of the iterative hypothesis refinement. Hereby, the main contribution of this work is the adaptive feature selection criterion based on the conditional mutual information. Also it is shown that such adaptive selection strategy is indeed used by people while performing visual classification.

Arbeitsgedächtnisdefizite lernbehinderter Kinder sind bisher vor allem im phonologischen Bereich nachgewiesen worden. Die eigene Studie untersucht mögliche Defizite im Bereich der zentralen Exekutive mit zwei Schwerpunkten: (a) Lassen sich bei der Steuerung selektiver Aufmerksamkeit spezifische Defizite Lernbehinderter identifizieren? (b) Zeigen sich Besonderheiten in den Alterszugewinnen selektiver Aufmerksamkeit? In der Untersuchung wurden Grundschulkinder gleichen mentalen und gleichen chronologischen Alters mit einer Gruppe lernbehinderter Kinder einer vierten Klasse verglichen. Zusätzlich wurden ältere Schulkinder (7. Klasse, 4. Klasse, 7. Klasse einer Sonderschule L) einbezogen, so dass auch prüfbar wird, inwiefern sich Alterszugewinne der kognitiven Funktionen bei lernbehinderten im Vergleich zu unauffälligen Schülern unterscheiden. Einbezogen wurden nur L-Schüler mit einem IQ < 85. Zur Erfassung der zentral-exekutiven selektiven Aufmerksamkeit wurden drei verschiedene Aufgabenanforderungen (TAP, Stopp-Signal, TEZEK) gewählt. Die Befunde deuten auf ein frühes Funktionsdefizit der lernbehinderten Kinder hin, das bis 14 Jahre weitgehend kompensiert werden kann.

Regular use of illegal drugs is suspected to cause cognitive impairments. Two substances have received heightened attention: 3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy’) and δ-9-tetrahydrocannabinol (THC or ‘cannabis’). Preclinical evidence, as well as human studies examining regular ecstasy consumers, indicated that ecstasy use may have negative effects on learning, verbal memory and complex attentional functions. Cannabis has also been linked to symptoms of inattention and deficits in learning and memory. Most of the published studies in this field of research recruited participants by means of newspaper advertisements or by using word-of-mouth strategies. Because participants were usually aware that their drug use was critical to the research design, this awareness may have caused selection bias or created expectation effects. Focussing on attention and memory, this study aimed to assess cognitive functioning in a community-based representative sample that was derived from a large-scale epidemiological study. Available data concerning drug use history allowed sampling of subjects with varying degrees of lifetime drug experiences. Cognitive functioning was examined in 284 young participants, between 22 and 34 years. In general, their lifetime drug experience was moderate. Participants completed a neuropsychological test battery, including measures for verbal learning, memory and various attentional functions. Linear regression analysis was performed to investigate the relationship between cognitive functioning and lifetime experience of drug use. Ecstasy and cannabis use were significantly related to poorer episodic memory function in a dose-related manner. For attentional measures, decrements of small effect sizes were found. Error measures in tonic and phasic alertness tasks, selective attention task and vigilance showed small but significant effects, suggesting a stronger tendency to experience lapses of attention. No indication for differences in reaction time was found. The results are consistent with decrements of memory and attentional performance described in previous studies. These effects are relatively small; however, it must be kept in mind that this study focussed on assessing young adults with moderate drug use from a population-based study.

<div>Haptic interfaces possess great potential for both transmitting information and affecting emotion. I present two studies exploring these two applications.</div><div><br></div><div>The first study investigates the ability to selectively attend to certain tactile stimuli while ignoring others. Understanding this ability is necessary when designing vibrotactile displays that present multiple simultaneous signals for information transmission. Participants in this study wore a tactile display on each arm. They were trained to identify nine stimuli varying in location and frequency and tested on stimulus identification under various conditions, depending on whether one or both arms were stimulated and whether one or both arms were attended to. The results provide empirical evidence for selective attention of vibrotactile stimuli and indicate that participants can selectively attend to three locations and two frequencies with high accuracy.</div><div><br></div><div>The second study explores whether haptics can enhance the perceived immersiveness, novelty, and creepiness of a haunted house. Vibrotactile stimuli inspired by natural phenomena were presented to the user’s palm, and concealed actuators rattled the user’s chair. Séance-themed audio and visuals provided narrative context. In a post-experience questionnaire, nineteen of twenty-two participants reported that haptic effects increased their sense of immersion. A follow-up experiment was conducted to compare the impact of using multiple, distinct haptic stimuli as opposed to repeating a single,</div><div>multiplex stimulus. The results demonstrate both the influence of context on stimulus interpretation, as well as the unique payoffs when stimuli are tailored for a particular context.</div>

The research domain on the Quality of Experience (QoE) of 2D video streaming has been well established. However, a new video format is emerging and gaining popularity and availability: VR 360-degree video. The processing and transmission of 360-degree videos brings along new challenges such as large bandwidth requirements and the occurrence of different distortions. The viewing experience is also substantially different from 2D video, it offers more interactive freedom on the viewing angle but can also be more demanding and cause cybersickness. Further research on the QoE of 360-videos specifically is thus required.The first goal of this thesis is to complement earlier research by (Tran, Ngoc, Pham, Jung, and Thank, 2017) testing the effects of quality degradation, freezing, and content on the QoE of 360-videos. The second goal is to test the contribution of visual attention as influence factor in the QoE assessment. Data will be gathered through subjective tests where participants watch degraded versions of 360-videos through an HMD with integrated eye-tracking sensors. After each video they will answer questions regarding their quality perception, experience, perceptual load, and cybersickness.Results of the first part show overall rather low QoE ratings and it decreases even more as quality is degraded and freezing events are added. Cyber sickness was found not to be an issue. The effects of the manipulation on visual attention were minimal. Attention was mainly directed by content, but also by surprising elements. The addition of eye-tracking metrics did not further explain individual differences in subjective ratings. Nevertheless it was found that looking at moving objects increased the negative effect of freezing events and made participants less sensitive for quality distortions. The results of this thesis alone are not enough to successfully regard visual attention as an influence factor in 360-video.