Relationship between crossover and modality shift effects in sequential reaction time performance of schizophrenic patients.

On the basis of reaction time measurement, two well-known experimental indicators of attentional dysfunctions in schizophrenia were studied. These are the crossover effect (COE), induced by alternating preparatory intervals, and the modality shift effect (MSE), induced by alternating stimulus modalities. For the first time, the relationship between these indicators was examined. Correlations of both indicators with clinical variables such as psychopathology, subjective complaints, duration of illness and medication were also analyzed. Subjects were 50 schizophrenic inpatients and 50 healthy controls, 21 women and 29 men in each group. While earlier results for COE and MSE were replicable, no correlation between the two was found, leading to the conclusion that they involve different aspects of attention not necessarily impaired to the same extent in all patients.