The literature describing psychological experiments with schizophrenics repeatedly reports findings regarding size constancy estimation in schizophrenics, or in specific subgroups of schizophrenics, which are claimed as confirming the assumption that such patients are characterized by disorders of attention with consequent inability to process depth cues (Venables, 1964; Weckowicz, 1957) or inappropriate scanning behavior (Silverman, 1964 a). Such findings are often quite contradictory, however (see part I of the present study). Most studies in this area proceed from the premise that schizophrenia involves specific disorders which bring about systematic distortions of the patients’ perceptual processes or judgment independently of the external stimulus situation. It is also taken for granted that even the most widely differentiated forms of schizophrenia respond in similar fashion to a given change in the external stimulus situation. Both these assumptions imply that schizophrenia involves a consistent internal psychological change with regard to external reality. This may agree well with some textbook descriptions of psychopathology, but certainly not with the realities of psychological processes.
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