This doctoral thesis attempts to clarify and further knowledge of the semantic memory impairments in schizophrenia. Methodology includes a comprehensive meta-analysis of relevant literature and a number of empirical studies enlisting people with a diagnosis of Alzheimer's Dementia and Acquired Brain Injury as control populations. The thesis argues that the semantic memory and categorisation deficits in schizophrenia are task- specific, once the effects of IQ are controlled for. Impairments are not likely to be due to a loss of semantic knowledge or a dysexecutive syndrome but may be caused by...