Shift of attention in schizophrenics, siblings of schizophrenics, and depressed patients.

This study investigated whether deviant types of attention, measured by reaction time, would characterize schizophrenics, depressives, and healthy siblings of the schizophrenic probands. Nineteen schizophrenics, 16 depressives, 15 healthy siblings of the schizophrenics, and 19 normals were tested on the cross-modal reaction time task. Two ways of conveying information about the impending imperative stimulus were compared to attempt to normalize schizophrenic cross-modal retardation. Deviant shift of attention was measured by cross-modal retardation, i.e., a greater than normal lengthening of reaction time to cross-modal vs. ipsimodal stimuli. Both schizophrenics and depressives showed deviant shift of attention to sound stimuli, but only schizophrenics were deviant to light stimuli. Anomalous cross-modal retardation was not normalized by the experimental manipulation. Both patient groups showed significantly slowed reaction time, suggesting deviances of general alertness. Depressed patients displayed anomalous sustained attention, indexed by significant lengthening of reaction time over trials. Siblings of schizophrenics did not differ significantly from controls on any aspect of reaction time performance. High magnitude of cross-modal retardation to sound and slow overall reaction time may be markers of psychopathological disorder rather than vulnerability. High cross-modal retardation to light may be a marker of schizophrenic disorder. Slowing of reaction time over trials is a potential marker of depressive disorder.