Implicit and Explicit Memory in Schizophrenia

Abstract

The aim of this thesis was to determine whether the core memory deficit in schizophrenia is better characterized by the implicit / explicit retrieval distinction or the perceptual / conceptual processing distinction. Memory was measured over three experiments using a range of implicit and explicit memory tasks that relied on perceptual or conceptual processing. A read - generate encoding manipulation was employed to operationally define tasks as perceptual or conceptual. Experiment 1 compared people with schizophrenia and controls on the implicit word fragment completion task (perceptual), and the explicit semantic cued recall task (conceptual). People with schizophrenia displayed intact priming on the implicit perceptual task and were impaired on the explicit conceptual task. Experiment 2 compared people with schizophrenia and controls on the implicit category association task (conceptual) and the explicit word stem cued recall task (perceptual). The results indicated that people with schizophrenia were impaired on both the implicit conceptual task and the explicit perceptual task. Experiment 3 explored this finding further by comparing people with schizophrenia and controls on implicit and explicit versions of the word fragment and semantic tasks that adhered to the retrieval intentionality criterion. The results demonstrated that priming/recall in people with schizophrenia was intact on the implicit perceptual, implicit conceptual, and the explicit perceptual tasks, while recall was impaired on the explicit conceptual task. Despite the inconsistency in results between Experiment 2 and Experiment 3, the findings indicate that dissociations among memory tasks in this clinical population may be better explained in terms of various memory systems rather than by a processing framework of memory.