Avoidance learning in schizophrenia: a dissociation between the effects of aversive and non-aversive stimuli

Patients with schizophrenia did not take significantly more trials than normal controls to learn to use a visual warning signal to avoid a non-aversive stimulus on a simple computer-administered avoidance learning task. When the stimulus to be avoided was aversive (i.e., a loud buzzer), however, the schizophrenic group could be divided into two subgroups based upon their performance; almost one half of the schizophrenic group failed to learn how to avoid this task successfully. The other half, like the normal controls and the closed head injury group in our previous studies, benefited from the aversiveness of the stimulus to be avoided, and learned to avoid more quickly than in the non-aversive condition. A post-hoc analysis of the differences between these two subgroups of the patients suggested that the discrepancy in learning was related to the age of onset of illness.