Global neurocognitive impairments have been observed during neuropsychological tests for patients with schizophrenia; however, similar findings have also been reported in patients with other psychiatric disorders. As such, it is unclear whether there are specific neurocognitive impairments in schizophrenia.
 Self-disturbance is considered a core symptom of schizophrenia, and is now being studied from the neurocognitive standpoint of an abnormal sense of agency (SoA). SoA refers to the feeling of initiating and controlling one's own actions and their effects in the outside world. We devised an agency-attribution task that evaluated explicit experiences of the temporal causal relationships between an intentional action and an external event. In our study, patients with negative symptom-predominant schizophrenia exhibited a markedly reduced SoA compared with normal controls. On the other hand, patients with paranoid-type schizophrenia demonstrated excessive SoA. Therefore, SoA may be a specific neurocognitive impairment in schizophrenia, as well as a possible state and trait marker of the illness. Here, we introduced the SoA paradigm, which may be a method to link clinical psychopathology with the biological mechanisms of schizophrenia. Further studies are required to clarify the pathophysiological mechanisms and establish curative treatments, including cognitive rehabilitation for schizophrenia.
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