Information processing and lateralization in schizophrenia.

This experiment investigated two current approaches in the study of schizophrenic thought, information processing and hemispheric specialization. Ten paranoid and ten nonparanoid schizophrenics, ten nonschizophrenic psychiatric controls, and ten normal controls were presented three tasks tachistoscopically. The tasks, letter-naming and dot enumeration of unstructured and structured arrays, were designed to elicit left and right hemisphere functioning through automatic and controlled information-processing strategies. Hemisphere effects were significant in the letter task with the left hemisphere superior to the right for all groups. Position effects were also significant, suggesting that reading habits determine this function and the ability was shared by all psychiatric groups. The normal control group identified a significantly greater number of letters than all other groups which may suggest that the lower performance of the psychiatric groups was due to a general level of psychiatric pathology. The two dot enumeration tasks indicated that, unlike the other three groups, the nonparanoid group processed the dots using an automatic strategy but only in the left hemisphere. Right hemisphere processing was essentially the same for all groups. The left hemisphere performance of the nonparanoid replicates that of a previous study and leads us to consider the left hemisphere dysfunction as specifically related to nonparanoid schizophrenics and the dysfunction as the inability to process information in a serial manner.