 Schizophrenic patients will perform: Alert TEA, Zimmermann and Fimm, 2005, Edinburgh laterality questionnaire Oldfield, 1971, IQ test IQ: PM38, Raven, 1960, and the PANSS Positive and Negative Syndrome Scale, Kay et al., 1987. Controls will only perform the laterality questionnaire. Then all will perform the affordance task, in which photographs of 20 objects of everyday life, typically graspable with one hand, are presented in 4 orientations. Participants have to respond in a graspable device, as quickly as possible, if the object is presented upright or inverted. 