Deficits in Source Monitoring in Subjects with Auditory Hallucinations May be Due to Differences in Verbal Intelligence and Verbal Memory.

Previous research has proposed that the experience of auditory hallucinations in schizophrenia represents a failure to monitor self-generated verbal mental imagery. However, recent neuropsychological investigations into this matter have provided inconclusive and even contradictory findings with respect to the proposed relationship. This study compared the performance of three groups of adult males, schizophrenic inpatients (hallucinators and nonhallucinators), and normal controls, matched for age, education, and medication, on a source monitoring task. Initial analysis indicated that performance on a Verbal IQ and Verbal Memory test were significantly related to performance on the source monitoring task. Comparisons between groups were made on the basis of state and trait group characteristics with respect to hallucinations. After controlling for the influence of Verbal IQ and Verbal Memory on task performance, no between-group differences were found for overall accuracy in attribution of self-generated items or in the number of self to experimenter misattribution errors. This finding suggests that the inconsistent findings previously noted in this field may be due to a failure to identify and control for these important covariates. The implications of these findings for theoretical models of hallucination are discussed.