The modality shift effect (MSE) shows that the reaction time (RT) of schizophrenia patients is longer when successive imperative stimuli are of different modality (e.g., light followed by sound) than when they are identical (e.g., sound followed by sound). The authors analyzed the RTs of 49 men: 21 had schizophrenia, 13 were alcoholic, and 15 were controls. The results from a standard paradigm to provoke the MSE indicated a considerably more pronounced MSE in schizophrenia patients than in the comparison groups. Another experimental condition was used to test whether the effect is due to the longer activity of neural traces in sensory pathways in schizophrenia patients or to changes in an entire stimulus response cycle. Results suggest that only a shift in modality and not in the required motor response lengthened the RTs of the schizophrenia patients more than of the other groups.