ABSTRACTION IS IMPAIRED AT THE PERCEPTUAL LEVEL IN SCHIZOPHRENIC-PATIENTS

This study investigates category learning in schizophrenia in order to evaluate abstraction abilities at the perceptual level. The participa nts learned about two categories of geometric shapes. The category exe mplars were presented successively. In the case of schizophrenic patie nts, longer exposure time and more stimulus presentations were used to counterbalance attention impairments. In spite of this, the perceptua l category learning was significantly impaired in the patient group. I n contrast, when the training procedure involved verbal category defin ition and not perceptual learning, the performance of schizophrenics w as similar to that of the healthy controls. These findings suggest tha t the perceptual learning of categories, but not free classification j udgements are impaired in schizophrenia, and that this impairment is n ot due to pure attentional disturbances. (C) 1998 Elsevier Science Ire land Ltd.