WHAT DETERMINES CONTINUOUS PERFORMANCE TASK-PERFORMANCE

The Continuous Performance Task (CPT) is widely used as an indicator o f cognitive dysfunction in schizophrenia. It is still unclear, however , exactly what this test measures. We examined the contribution of mot or speed, reaction time measures, mental effort, and level of psychopa thology to the performance on a double-stimulus CPT This study include d schizophrenia patient groups, depressive patient groups, and patient and normal control groups. Subjects were retested twice: once after 1 week and again at 3 months. In patients with schizophrenia or depress ion, the sensitivity measure (d') was strongly and consistently associ ated with motor speed and with the standard deviation of reaction time s (response variability) to target stimuli. The association with respo nse variability was also found at followup tests in the control groups . We conclude that in patients with schizophrenia or depression, the s ensitivity measure of a double-stimulus CPT is associated with cogniti ve mechanisms that determine motor proficiency and response variabilit y.