Enhanced vividness of mental imagery as a trait marker of schizophrenia?

We assessed the vividness of mental imagery in schizophrenia patients in the context of psychopathology and cognitive abilities. A questionnaire on the vividness of mental imagery (Questionnaire Upon Mental Imagery [QMI]) and a hallucination scale were administered to 50 patients with paranoid schizophrenia. The related perceptual and cognitive skills, general intelligence level, and psychomotor speed were measured as covariates with a battery of performance tests. All measures were statistically compared to a group of 50 age- and sex-matched healthy controls. The schizophrenia group obtained higher values both for vividness of imagery and occurrence of hallucinations. These differences were independent of general intelligence and psychomotor speed and did not correlate with individual psychopathology. The correlation between the hallucination and imagery scales themselves was very low. These results suggest that patients with schizophrenia experience a significantly greater vividness of mental imagery than healthy controls, which does not seem to be an effect of other group differences or individual psychopathology (e.g., frequency of hallucinations). Vividness of mental imagery might thus prove to be an independent trait marker of schizophrenia.