Asymmetry of information processing in hallucinators and nonhallucinators

In previous work we had developed evidence suggesting that hallucinating schizophrenics differ from nonhallucinators in the pattern of errors made in a shadowing task. Non hallucinators appeared to be less willing to guess when they were unsure. The errors of the hallucinators seemed more semantically elaborate. The experiment had not been designed to study these factors and the current experiment was conducted using a technique reported by Pisoni et al. These workers had studied normal Ss in an immediate recall task, using semantically well integrated (SWI) or poorly integrated (SPI) sentences. Pisoni et al. had shown that right ear presentation produced more accurate recall of SWI as compared to SPI sentences, whereas left ear presentation failed to discriminate these sentences. Utilizing the methods of Pisoni et al., we replicated their findings in a normal control group. The results from our hallucinating and nonhallucinating groups were different from each other, the nonhallucinators being less accurate, discriminating semantic integration level on left rather than right ear input, and making more fragmented errors. Little support could be found for attributing this pattern of performance to nonspecific aspects of the procedures. It appears that the nonhallucinators process information differently from hallucinators. These differences may reflect alterations in language development. It is speculated that such differences might be consistent with interference with the development of brain asymmetry.