While enormous strides have taken place in our understanding of schizophrenia, the interpretation of most studies of schizophrenic patients is complicated by the fact that chronic schizophrenia is an "end-stage" disease with evidence for generalized pathology in multiple brain systems, probably involving the convergence of a number of distinct etioligic factors. As a result, it may be difficult to disentangle the specific brain mechanisms involved in its pathogenesis. Schizotypal personality disorder (SPD) respresents a disorder clearly documented to be related to schizophrenia and is the most common phenotype for the genetic diathesis to the schizophrenia-related disorders. The specific major objectives of the proposal are to 1) identify and clinically diagnose 75 SPD patients, 75 other, non-schizophrenia related, personality disorder patients, and 75 normal control subjects over 5 years; 2) characterize their cognitive function in these domains, and 3) evaluate performance on these tasks in each cohort following a randomized double-blind placebo controlled administration of amphetamine (30 mg).