Keeping track of your inner voice: an exploration of speech-monitoring deficits in schizophrenia




Sheer, Jeffrey Brian

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During the last 20 years, a body of research has emerged suggesting that deficits in the self-monitoring of willed intention to act may be responsible for the expression of positive symptoms in schizophrenia (Frith, 1992). Empirical evidence supporting this theory indicates that schizophrenics with positive symptoms are impaired on motor and speech based tasks that involve monitoring of internal cognitive mechanisms and behavior plans, but are less impaired when monitoring external sensory feedback. The current project extends this research by comparing the performance of two groups of schizophrenics (hallucinators, n=16; and nonhallucinators, n=15) with a group of nonpsychotic psychiatric patients (n = 15) on measures of speech monitoring of internal and overt speech. On two measures of internal speech monitoring (silent reading and identification of speech errors in a white noise environment), the schizophrenics were found to be impaired relative to controls; however, the schizophrenics were also impaired on a task of self-monitoring when they had access to external feedback. Analysis of the subgroups data (hallucinators vs. nonhallucinators) indicated very similar performances across tests and no significant differences were identified, with the exception of the silent reading test in which the hallucinators did perform significantly worse. These results indicate that the speech-monitoring deficit in schizophrenia is not limited to the internal speech plan, but can also involve a failure to monitor overt speech, contrary to previous report. Furthermore, speech-monitoring deficits are not limited to schizophrenics who experience hallucinations. An additional experiment involving delayed auditory feedback (DAF) was also conducted to replicate a previous finding in the literature that schizophrenics were more dysfluent in DAF. On the DAF task, the combined schizophrenic group were found to be more dysfluent than controls, and there were no differences between the two schizophrenic subgroups. Further correlational analysis revealed a strong relationship between the level of dysfluency in DAF and self-monitoring impairment. While the results of the experiment were similar to those found by previous authors (Goldberg, Gold, Coppola, & Weinberger, 1997), the correlational analysis allows for an explanation of dysfluency in DAF based on self-monitoring.