The effects of varying nois and information loads on visual information processing of schizophrenics

Abstract

PROBLEMPrevious research on the span of apprehension@, lo, 'l) has shown that schizophrenics perform less well than controls when noise letters are presented with target letters. These researchers have hypothesized that the schizophrenic deficit is due to a malfunction of the central processor rather than t o a sensory store trace of the incoming stimulus. Accordingly, it has been argued that the span of apprehension task (' ) provides a convenient measure of the central processor deficit. la) suggest that as signal-noise similarity increases, performance on visual processing tasks decreases. Although researchers have investigated the qualitative variations of noise, few have investigated the quantitative variation of noise. A study by the present author that used a span of apprehension task with chronic schizophrenics suggests that chronic schizophrenics and institutionalized tubercular controls manifested a greater deficit on tasks of (1) increasing information levels and (2) increasing noise levels as compared to community controls.Another study that used college students (2) established that a significant interaction between noise and information levels was present. When the interaction was analyzed, significant differences were found between noise-level groups in the broad range of channel capacity suggested by Miller@), i e . , 4, 5, 6, 7, 8, 10 and 12Most studies ( a * elements.The Dresent studv was designed to test whether such an interaction would be found wiih chronic and acute s&izophrenics. Increasing noise levels may impair performance to a greater degree with schizophrenics than controls as the number of elements to be processed approaches channel METHOD 12).