COGNITIVE FILTERING IN SCHIZOPHRENICS IN A DICHOTIC LISTENING TASK
KAPLAN, RALPH VICTOR
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This study utilized the technique of dichotic auditory presentation in an attempt to assess the applicability of the cognitive filter theory of schizophrenic attentional dysfunction in understanding postulated underlying differences between schizophrenics and normals. Furthermore, it sought to explain variability in the operation of the postulated cognitive filter in terms of subgroups of schizophrenia based on types of thought disorder. Four discrete subgroups of twenty subjects each were categorized according to an overinclusion/overexclusion dimension by use of the card-sorting method devised by Loren Chapman. The four subgroups, overincluders, overexcluders, mixers and neutrals were compared with each other as well as with twenty normal controls. In all, one hundred subjects were tested in a dichotic shadowing task with the instructions to "listen to and repeat the words from the left ear while ignoring the right ear." This task was carried out first without distraction, then with distraction. Recall, recognition and discrimination tasks followed. A 2 (Conditions) x 5 (Subgroups) Analysis of Variance with repeated-measures on the first factor revealed that a cognitive filter was differentially operative according to subgroup type, especially at the input stage of the shadowing task. In contrast to previous research, evidence of differentially-operative cognitive filter deficits was also found to play a role at the recall and recognition stages, but in combination with other kinds of basic deficits, such as information encoding, subjective organization, memory retrieval, etc. In addition, the dimension of overinclusion/overexclusion was found to run independently of the three more traditional dimensions of acute/chronic, process/reactive, and paranoid/nonparanoid.