“When we consider the immense human significance of sleep, the absolute necessity for us to spend a considerable part of our lives in abject mental annihilation, it is remarkable how little we know about it. …” In these words, Sir John Eccles introduced the recently published Ciba Foundation Symposium on “The Nature of Sleep” (3), in which are described many of the advances which have been made in recent years in our attempts to understand the phenomena which are involved in the state of sleep. In one of the papers included in this Symposium, Bremer (2) reviews the work which has been reported since 1954 on the neurophysiological mechanisms involved in sleep. The relationship of dreaming to the depth of sleep has been investigated by such workers as Kleitman (5), Dement (4) and Wolpert (11). These studies have been made possible by the application of modern techniques of measuring mental activity. The use of electroencephalographic methods has allowed an approximate classification of the different levels of sleep which enables different workers to adopt a standard frame of reference. Measurements of rapid eye movements and of changes in muscle potential during sleep have provided more objective methods of assessing dream activity. Other recent studies have attempted to make an objective assessment of the physical and mental effects of sleep deprivation (Morris et al., 7, Bliss et al., 1, Murray et al., 8, Wilkinson, 9, Williams et al., 10).
Frequent references have been made to the similarities between highly creative and psychotic thinking. This study attempts to test the hypothesis that one explanation for such a correspondence lies in the fact that individuals in both these populations habitually employ common attentional strategies which cause them to sample an unusually wide range of available environmental stimuli. A group of highly creative adults and a group of equally intelligent but low creative adults were compared with a group of acute non-paranoid schizophrenic adults on three tests designed to assess attentional and other cognitive styles. The results offer support to the view that both highly creative and schizophrenic individuals habitually sample a wider range of available environmental input than do less creative individuals. In the case of the schizophrenic this involuntary widening of attention tends to have a deleterious effect on performance, while, in contrast, the highly creative individual is more able to successfully process the greater input without this incurring a performance deficit.
In recent years there has been increasing experimental evidence that specific disturbances of perception occur in schizophrenia. Reduced size constancy in schizophrenic patients has been reported in studies by Raush (13), Crookes (6), and Weckowicz (16). Further investigations by Weckowicz and his colleagues (17), have also demonstrated reduced distance constancy in schizophrenia. (The retinal image of an object alters proportionately with the distance at which it is perceived. Size and distance constancy refer to our normal ability to compensate for changes in the stimulus and thereby to retain a stable perception of the object.) Brengelmann (3) and Angyal (1) have shown that schizophrenic patients have difficulty in reproducing briefly exposed visual stimuli. Penrose (12) has shown that schizophrenics perform poorly in a variety of tests involving visual discrimination.
In recent years an increasing number of workers investigating schizophrenic behaviour have concluded that many of the symptoms found in schizophrenia are related to a disturbance in the selective and inhibitory functions of attention. One of the earliest statements of this argument is found in Norman Cameron's (1938, 1939, 1944) concept of “over-inclusion”, which he used to describe the schizophrenic patient's tendency to include many elements irrelevant to the central idea in his thinking. Shakow (1962) reached the following conclusions in summarizing his own psychological studies of schizophrenia—“It is as if, in the scanning process which takes place before the response to stimulus is made, the schizophrenic is unable to select out the material relevant for optimal response. He apparently cannot free himself from the irrelevant among the numerous possibilities available for choice.” Weckowicz and Blewett (1959), in their studies of alterations in perceptual constancy in schizophrenic patients, interpreted their findings as suggesting that the patient's basic difficulty was that of “an inability to attend selectively or to select relevant information“. Venables and his colleagues (1959, 1962, 1963), in a series of studies on the arousal level of schizophrenic patients, also concluded that many of the behavioural abnormalities demonstrated were due to variations in the range of attention. In a series of investigations carried out by Payne and his colleagues (1960, 1961, 1963) to develop Cameron's concept of over-inclusive thinking in schizophrenia, the authors utilized Broad-bent's (1958) model of selective attention to postulate that this form of thought disorder is basically due “to a defect in some hypothetical central filter mechanism, the function of whichis to screen out irrelevant data both internal … and external … to allow for the most efficient processing of incoming information”.
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