Speech misattribution bias in schizophrenia offers clue to hallucinations
MedWire News: Misattribution of self-generated speech to others may underlie auditory verbal hallucinations (AVHs) in patients with schizophrenia, research suggests.
M Stephane, from Veterans Affairs Medical Center in Minneapolis, Minnesota, USA, and colleagues also report that the pronoun used in speech could impact the self-other speech distinction in some types of AVHs.
However, the acoustic quality of the heard speech, ie, the gender, did not affect the self-other speech distinction.
“This finding relates AVHs indirectly to a disorder of speech processes that involve linguistic meaning rather than language phonetics,” the team writes in the journal Psychological Medicine.
The researchers asked 39 patients with schizophrenia and 26 mentally healthy individuals to distinguish between sentences that were self-generated, other-generated, or non-generated.
In an initial presentation phase, the participants read aloud sentences that appeared on computer screen (self-generated), or listened to sentences read to them in a neutral tone by the computer while the screen remained blank (other-generated).
Then in a test phase, five each of these different types of sentences were presented randomly along with five new sentences that had not previously been read or heard (non-generated).
The sentences were carried out in 12 blocks, which included the heard sentences being read in a female voice in six blocks and in a male voice in six blocks. Also, the tests included sentences written in the first, second, or third person. The participants heard and read a total of 120 sentences.
Patients with schizophrenia were significantly less likely to be able to distinguish between self-generated and other-generated speech, tending to misattribute self-generated speech to others.
The 31 schizophrenia patients with lifetime AVHs also differed significantly from controls in misattributing self-generated speech to others, but there was no difference compared with non-hallucinating patients. The researchers suggest that this may be due to the small number of non-hallucinating patients.
The pronoun variable affected the ability to recognize self- and other-generated speech for the population as a whole but did not differentiate between patients and controls. “This lack of effect could be related to the hallucinating patient group combining patients with AVHs in the second person and patients with AVHs in the third person,” the researchers suggest.
“Patients with second-person AVHs could have prominent misattribution bias of speech in the second person, and patients with third person AVHs could have prominent bias with speech in the third person.”
Thus, “these factors could become significant with a larger group of patients divided according to the characteristics of their hallucinations,” the team concludes.
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By Lucy Piper