Attentional processing in schizophrenia: experimental induction of the crossover effect
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A target group of 16 schizophrenics were compared with 48 college students on both the Rodnick and Shakow (1940) reaction time (RT) paradigm and a dual-task procedure designed to produce the early crossover effect innormals with a balanced order design. The dual-task procedure required subjects to perform a simple version of the continuous perfectionism task (CPT) during all of the preparatory intervals of the classical RT task. Analysis of the RT data showed significantly earlier RT crossover and greater RT slowing across groups on the dual-task procedure. As expected, schizophrenics were significantly slower and had significantly earlier crossover scores across tasks. A planned comparison showed that the experimentally induced early mean crossover of 8.01 sec found in the normal group on the dual-task procedure closely approximated, and was not significantly different from, the mean crossover of 8.36 sec for schizophrenics on the standard task. The increased RTs found in normals on the dual-task procedure never reached the pathological level of overall slowness shown by the schizophrenics. The results are viewed as compatible with both information processing theory and Shakow's (1962) loss of set explanation of schizophrenic attention deficit, and incompatible with Steffy and Galbraith's (1974) redundancy deficit theory. The findings suggest that separate neuropsychological mechanisms of cognitive preparatory attention and a more automatic vigilance form of attention may underlie the regular and irregular RT procedures of the traditional RT task.
Key wordsschizophrenia attention information processing crossover reaction time
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