Hemispheric preference of paranoid and nonparanoid schizophrenics

Recent evidence indicates that paranoid and nonparanoid schizophrenics exhibit differential hemispheric deficits in specific types of processing tasks which may reflect a preference of one hemisphere over another. To test this hypothesis, face and letter-recognition tasks were tachistoscopically presented, both bilaterally and unilaterally, to paranoid and nonparanoid schizophrenics, nonschizophrenic psychiatric controls, and normal controls. In the unilateral presentation of letters, all groups exhibited right visual field superiority, producing no group differences. In the unilateral presentation of faces, paranoids were found to recognize fewer faces when presented to the left visual field as compared to the control groups. With bilateral presentation of both a face and a letter no group differences were found; all groups exhibited a right visual field superiority in processing both types of stimuli. The bilateral presentation of two faces produced a right visual field superiority in all groups. In the bilateral presentation of two letters, nonparanoids were found to recognize fewer letters when presented to the right visual field as compared to control groups. Thus, paranoids and nonparanoids were found to exhibit differential hemisphere deficits. The paranoid deficit is in processing faces when presented to the left visual field-right hemisphere while the nonparanoid deficit is in processing letters presented to the right visual field-left hemisphere. These results are discussed in terms of information-processing styles and strategies as differentially employed by the paranoid and nonparanoid schizophrenic.