Agency, the sense of presence, and schizophrenia.

The objective of this work is to evaluate the impact of agency deficiency on presence. We hypothesize that a deficit in agency, such as occurs in schizophrenia, has repercussions on the sense of presence as well as on performance in a sensorimotor test involving the body. Nineteen healthy controls and 19 stable patients with schizophrenia, matched by age and gender, participated in the study. We used new interactive technologies that enable the users to physically interact with a virtual environment and simultaneously sees themselves performing the actions. Two conditions were balanced: the control condition in which the participant see himself or herself doing the test, and the mask condition, in which the central part of the participant's body is hidden. At the end of the test, all participants completed a questionnaire on presence. The results show that control participants performed better than those with schizophrenia in the control condition. On the contrary, in the mask condition, their performance was significantly lower, whereas participants with schizophrenia obtained the same score as in the control condition. Controls also rated higher in the scale of presence than did participants with schizophrenia. Those results seem to corroborate a relationship between agency and presence. The body awareness and the self in schizophrenia are discussed in the light of agency.