In this study, we propose to administer cognitive tests to schizophrenic patients and to neurologic patients who will serve as contrast groups for neuropsychological studies of patients with schizophrenia. These include studies of Alzheimers disease to dissociate size and organization of lexicon and ADHD to understand error patterns on CPT-type tests of attention and vigilance. However, the majority of studies will examine schizophrenia in relation to normal controls.