Schizophrenia affects approximately 1 percent of the population worldwide. It typically involves hallucinations and delusions, also known as psychotic or positive symptoms. Markedly impaired social skills and cognitive deficits, also known as negative symptoms, are also core features. In fact, schizophrenia was originally called dementia praecox (i.e., early onset dementia, to highlight the impairment of cognition. The cognitive domains most often affected by schizophrenia include attention, memory, and language. These deficits are evident even before the onset of positive symptoms (during the so-called "prodrome") and in untreated schizophrenic patients. It is therefore unlikely that the cognitive features of schizophrenia result simply from chronic illness, institutionalization, or medication side effects. Most important, the degree of cognitive decline is the best predictor of functional outcome: that is, how the patient will do in the community once the most severe psychotic features have abated. Here we will...