Distractibility in schizophrenia: The effects of stimulus modality, task difficulty, and practice

Previous research has suggested that thought disorder in schizophrenia may be linked to disturbances in cognitive processes such as attention. The strongest evidence has been in the area of greater distractibility in schizophrenic patients on auditory digit-span tasks. The trend now is to look for ways in which this greater distractibility may be used as a marker for vulnerability to schizophrenia. However, little is known about the stability of patients\u27 performance on these attentional tasks over time, or the effects of practice on performance. Also, there has been little conclusive evidence of greater distractibility in schizophrenic patients using visual stimuli. In the present study, seventeen chronic schizophrenic inpatients and fifteen nonpsychiatric control subjects were given two tasks measuring distractibility. One was an auditory digit-span task, the other a visual card-sorting task. Subjects performed each task twice, on two consecutive days. Performance of patients and controls was compared using a mixed design analysis of variance to see whether: (1) patients and controls differed significantly in amount of distractibility on any condition of either task, (2) task difficulty affected distractibility of patients and controls differently, and (3) practice affected distractibility of patients and controls differently. Results showed that patients were significantly more distractible than control subjects on the easy condition of the digit-span task only. There were no differences between groups on the card-sorting task. On both tasks, patients and controls were similarly affected by task difficulty and practice, with poorer performance on the more difficult conditions and improved performance with practice. Given the overall lack of differences between patients and controls, it was concluded that greater distractibility in schizophrenia is a small effect that is not characteristic of all schizophrenic patients, at least not all the time