The present dissertation aims to evaluate the phenomenon of visual masking as a tool for studying visual awareness focusing on two-alternative forced choice (2AFC) discrimination tasks. Two existing theories of masking - Bachmann's (1984) perceptual retouch theory and Marcel's (1983) recovery theory - are discussed along with the global neuronal workspace theory of awareness (Baars. 1989; Dehaene, Kerszberg, & Changeux, 1998). Performance accuracy on Semantic discrimination is compared to that on Orthographic discrimination as an indication of a potential difference between semantic and orthographic processing of masked word stimuli presented for 40 ms and 50 ms. This is further compared to an e-detection task previously used as an indicator of awareness in some masked priming experiments. Together, these tasks are further evaluated in terms of their relationship with participants' subjective reports collected in the form of confidence ratings. The implications and predictions drawn from the theories of masking and visual awareness as well as the notion of partial awareness (Kouider & Dupoux, 2001) are assessed taking into account the data obtained in the current experiments.The relevance of these data for masked priming is determined by performing a comparison between 2AFC discrimination and detection tasks, and the lexical decision task. An ERP study is also presented, in which Semantic and Orthographic discrimination as well as e-detection are paired with confidence ratings and electrophysiological recordings in search of an ERP component that can be correlated with both subjective (confidence) and objective (performance) measures of awareness. A binding account of visual awareness with special attention paid to visual masking is proposed and compared to the three existing theories.

京都大学 / 新制・課程博士 / 博士(人間・環境学) / 甲第23264号 / 人博第979号 / 新制||人||232(附属図書館) / 2020||人博||979(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 阪上 雅昭, 教授 谷口 一美, 准教授 森口 佑介 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

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La tâche de kinématogramme de points aléatoires est utilisée avec le paradigme de choix forcé entre deux alternatives pour étudier les prises de décisions perceptuelles. Les modèles décisionnels supposent que les indices de mouvement pour les deux alternatives sont encodés dans le cerveau. Ainsi, la différence entre ces deux signaux est accumulée jusqu’à un seuil décisionnel. Cependant, aucune étude à ce jour n’a testé cette hypothèse avec des stimuli contenant des mouvements opposés. Ce mémoire présente les résultats de deux expériences utilisant deux nouveaux stimuli avec des indices de mouvement concurrentiels. Parmi une variété de combinaisons d’indices concurrentiels, la performance des sujets dépend de la différence nette entre les deux signaux opposés. De plus, les sujets obtiennent une performance similaire avec les deux types de stimuli. Ces résultats supportent un modèle décisionnel basé sur l’accumulation des indices de mouvement net et suggèrent que le processus décisionnel peut intégrer les signaux de mouvement à partir d’une grande gamme de directions pour obtenir un percept global de mouvement. / Random dot kinematograms are used in visual psychophysics with the two-alternative forced-choice paradigm to study the process of simple perceptual decisions. Mathematical models of this process assume that stochastic motion evidence for the two alternative choices is encoded in the brain, and that the difference in evidence is accumulated towards a decision bound. However, no study to date has tested this assumption using stimuli with different levels of mutually opposing evidence in both directions. This thesis presents the results of two experiments using two novel stimuli with opposing coherent motion evidence. Over a variety of competing evidence combinations, subject performance was based on the net difference in the opposing signals. Furthermore, task performance was similar with both types of stimuli. These results support a decision model based on the accumulation of net evidence, and suggest that the decision process is capable of integrating motion evidence from a wide range of directions to obtain a global percept of motion.