Information Processing in Schizophrenia: The Effect of Varying the Rate of Presentation and Introducing Interference

Payne and McGhie offer explanations of schizophrenic thought disorder which emphasize a breakdown in the selectiveness of Broadbent's filter. Yates has observed that an explanation emphasizing the slowness of information processing in schizophrenia equally well follows from Broadbent' model and accords with the experimental literature. Eighteen male chronic schizophrenics and nine male psychiatric nurses matched for age and intelligence were asked under one experimental condition (the complete recall condition) to reproduce digits presented dichotically at three different rates of presentation, and under another condition (the interference condition) to reproduce only those digits received through a designated channel. There were four different length lists and four presentations of each list length. The chronic schizophrenics were divided into two groups of nine in accordance with their scores on the Venables‐O'Connor Paranoid Scale. An analysis of variance was performed in the complete recall condition using difference scores obtained by subtracting the number of digits correctly reproduced in order in the second half list from the number reproduced from the first half list. In the interference condition the scores employed were the total number of relevant digits correct, the number of relevant lists completely correct and the number of digits reproduced from the irrelevant channel. While group was a significant source of variance in the complete recall condition, contrary to prediction from Yates' theory, the interaction of group and rate was insignificant. This was the case even when the analysis was repeated using difference scores adjusted for variation in the reproduction of the first half list and only the normal and non‐paranoid schizophrenic groups compared. There was some evidence that the recall of the second half list improved for all groups at faster rates of presentation. Nor were the three groups differentially affected by variations in the rate of presentation under the interference condition. As predicted from Payne and McGhie, however, the schizophrenics were most affected by distraction from the irrelevant channel. It is suggested that at slower rates of presentation the digits presented first in the complete recall condition are rehearsed with the result that the reception of those presented later is confused. The need to consider the total length of time over which information is to be processed is discussed. The view is put that retardation in schizophrenia may constitute a secondary adjustment to a state of information overload and an empirical test of this hypothesis proposed.