In its many manifestations, psychosis leads to a number of clinical and philosophical debates. Despite their practical and conceptual importance, a number of these debates remain unresolved. Appealing to the connection between phenomenological descriptions, empirical evidence, and philosophical analysis, this dissertation is devoted to the careful examination of five of the main debates surrounding the occurrence of delusions of thought insertion, one of the most complex and severe symptoms of psychotic disorders. Roughly speaking, patients suffering from thought insertion report that external agents of different nature have placed certain thoughts into the patients' minds. The introduction to this compilation clarifies the main distinctions underlying the general discussions about delusions and the specific debates surrounding thought insertion. The introduction is followed by a collection of five papers. The first paper tries to explain the way in which subjects self-attribute their own conscious thoughts in terms of agency. The second paper, assuming that delusions are a type of belief, engages with the discussion about the role that experiential abnormalities have in the process of formation of the delusional belief of thought insertion. The third paper examines the role that affective impairments might have in the process of production of thought insertion, an issue that is often overlooked by current dominant approaches to thought insertion. Taken altogether, the first three papers of this collection offer a novel understanding of the aetiology and architecture of thought insertion. The fourth paper examines a much larger discussion that overlaps with the debate about the subjective features of thought insertion. It is argued that cases of thought insertion - in conjunction with other psychotic phenomena - undermine the current self-presenting theory of consciousness, a theory meant to explain the most fundamental subjective character of conscious experiences. Finally, the fifth paper of the compilation engages with a more general discussion about the nature and role that delusions might play in a subject's life. It is argued against the dominant view that there are good reasons to characterize a certain type of monothematic delusions (including some cases of thought insertion) as biologically adaptive.

Over the course of my PhD I have investigated issues related to two main areas of investigation in cognitive science, namely Schizophrenia and Metacognition. My dissertation is divided in two parts: the first part includes three experimental studies (two studies in healthy subjects and one study in people with schizophrenia) and two theoretical studies addressing specific aspects of schizophrenia; the second part includes four theoretical studies addressing the role of metacognition in specific debates in philosophy and cognitive science of perception. I have explored two symptomatic expressions of schizophrenia, thought insertion and experiences of activity, as well as a potential cognitive bias, namely the potential presence of perceptual persistence biases. With respect to metacognition, I have investigated ways in which consideration of the role of metacognitive feelings (the experiential output of metacognitive processes) could shed new light on important current debates in analytical philosophy and cognitive science. The issues I have focused on are: the problem of hallucinations, the debate about cognitive penetrability (i.e., whether or not higher-order cognitive states may influence perceptual processes), the perception of absences and sensory substitution.

Au cours de mon programme doctoral j'ai mené plusieurs recherches, à la fois conceptuelles et empiriques, se rapportant à deux champs d'investigation importants des sciences cognitives : la schizophrénie et la métacognition. Ma dissertation se divise en deux grandes parties. La première partie inclue 3 études expérimentales (deux études menées sur des échantillons de sujets sains et une étude menée sur des individus atteints de schizophrénie) ainsi que deux études théoriques adressant des aspects spécifiques de la schizophrénie. La seconde partie présente quatre études théoriques portant sur l'apport de la métacognition dans certains débats vigoureux présents au sein de la philosophie analytique et des sciences cognitives. J'ai donc exploré deux symptômes de la schizophrénie -l'insertion de pensées et les expériences d'activité- ainsi qu'un potentiel biais cognitif ; à savoir, la présence de phénomènes aberrants de persistance perceptive. En ce qui concerne le thème de la métacognition, j'ai examiné la manière dont les sentiments métacognitifs (l'output phénoménologique des processus métacognitifs) pouvaient éclairer d'une nouvelle lumière certains débats importants de la philosophie et des sciences cognitives. Je me suis ainsi concentré tour à tour sur le problème des hallucinations ; sur le débat concernant la pénétrabilité cognitive (l'hypothèse que nos croyances peuvent influencer profondément nos expériences perceptives) ; sur la perception des absences et sur le cas de la substitution sensorielle. / Over the course of my PhD I have investigated issues related to two main areas of investigation in cognitive science, namely Schizophrenia and Metacognition. My dissertation is divided in two parts: the first part includes three experimental studies (two studies in healthy subjects and one study in people with schizophrenia) and two theoretical studies addressing specific aspects of schizophrenia; the second part includes four theoretical studies addressing the role of metacognition in specific debates in philosophy and cognitive science of perception. I have explored two symptomatic expressions of schizophrenia, thought insertion and experiences of activity, as well as a potential cognitive bias, namely the potential presence of perceptual persistence biases. With respect to metacognition, I have investigated ways in which consideration of the role of metacognitive feelings (the experiential output of metacognitive processes) could shed new light on important current debates in analytical philosophy and cognitive science. The issues I have focused on are: the problem of hallucinations, the debate about cognitive penetrability (i.e., whether or not higher-order cognitive states may influence perceptual processes), the perception of absences and sensory substitution.