Auditory sensory gating, a neural mechanism thought to reflect sensory information processing and affect cognition, is diminished in people with schizophrenia. Auditory sensory gating has been associated with the 7 nicotinic acetylcholine receptor, a brain receptor that is important for cognition and can be activated by nicotine. Activation of this receptor using an agonist medication, such as tropisetron, may produce the same positive effect that nicotine has on cognition. This study will determine the effectiveness of using tropisetron as supplemental therapy to the atypical neuroleptic risperidone in people with schizophrenia.