Ziprasidone is a newer drug intended for the treatment of the symptoms of schizophrenia. This new drug may have an added benefit of being able to help with some of the difficulties in problem solving and memory that many patients with schizophrenia experience. The present study wants to look at ziprasidone and two other drugs frequently used to treat the symptoms of schizophrenia (risperidone and olanzapine) to see if problem solving and memory get better with ziprasidone treatment. Moreover, we will look at symptoms and how they change with treatment.