Delusions of control in schizophrenia may be due to a de¢cit in the generation of an e¡erence copy, used to distinguish between self generated and externally imposed changes in the environment. This hypothesis was tested using a framework that di¡erentiated automatic and controlled levels of motor behavior. Subjects resisted collisions that were either self or externally imposed. The grip to load force correlation (response accuracy) and the overall grip force level used (response e⁄ciency)

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... measured. Controls improved both accuracy and e⁄ciency of their grip force responses in self compared to externally imposed collisions. Patients improved accuracy but not e⁄ciency of motor response. There was no di¡erence between patients with and without delusions of control.These results refute the hypothesis of a perturbed e¡erence copy in patients with delusions of control.We rather propose that schizophrenia globally preserves the automatic level but a¡ects the controlled, more voluntary level of motor behavior. NeuroReport13:1537^1539