Background: External misattribution of internally generated speech has been implicated in several cognitive models of psychotic symptomatology as the process by which internal percepts become hallucinations. Different strands of research have suggested that a) information is externally misattributed irrespective of meaning, conferring a risk for hallucinations, b) negative or derogatory self-generated percepts are externally misattributed leading to persecutory hallucinations, and c) that, in some people who have experienced childhood trauma, post-traumatic intrusive memories of trauma are externally misattributed to become hallucinations.
Methods: These strands of research were investigated with a group of people with first episode psychosis (n=44) and matched non-psychiatric controls (n=26) who completed psychopathology measures and underwent a source monitoring task using positive, neutral, negative and trauma words.
Results: Those with hallucinations showed no external misattribution bias across all words, or specifically for negative words. Those with childhood trauma showed no externalising bias for trauma words. Those with hallucinations did show an externalising bias towards positive words.
Conclusions: The results suggest that external source monitoring bias may not be central to the cognitive processes underlying hallucinations early in the course of psychotic illness. The theory linking childhood trauma and external source misattribution was not supported.
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