A psychological study of paranoia and delusional thinking

Abstract

In this thesis seven case studies of psychotic or borderline psychotic functioning were presented and an experimental study was reported and discussed involving the participation of 17 previously deluded psychotic volunteers and 42 non-psychotic volunteers. It was theorised that delusional thinking was permitted and eventually incited by an amplification of "confirmation bias" - the bias to seek and accept data and ideas which confirm a hypothesis at the expense of that which refutes it. The case study work provided supporting evidence for this. In the experimental study psychotics, especially paranoid psychotics, were higher on confirmation bias in a visual task and markedly higher in this bias on a verbal task. The bias was linked with high left hemisphere cortical activation and low right hemisphere cortical activation. Tentative evidence was presented that high confirmation bias was linked with low left hemisphere limbic activation and high limbic activation in the right hemisphere. It was also theorised that delusional thinking would be encouraged by high creativity given its set-breaking character. Scores on tests of creativity provided evidence that non-paranoid psychotics were more creative than paranoid psychotics but not more so than non-psychotics. The non-psychotic groups were, however, guite talented and may have presented the medicated recovering psychotics with guite a stiff challenge. Parallels (and differences) were drawn between delusional and mystical thought and it was argued that the two are closely related. The results of the research were integrated into a holistic multi-process theory of delusional thinking in which arousal, hemisphere differences and biochemical factors were seen as inter-related with more executive-guided gualitative aspects of the psychotic's life. Hence cerebral processes underlying their chief goals, needs and attributions were seen as interacting with more local brain processes to eventuate the delusional state.