Mental state representation in schizophrenia.
From a literature review, it was concluded that schizophrenia primarily
involves deficits in conscious, controlled processing. This was shown to be
compatible with Frith's (1992) neuropsychological model of impaired metarepresentation
in the disorder. There is strong evidence that patients with paranoid
symptoms or behavioural signs have deficits in the representation of others' mental
states ('theory of mind'; ToM), but two recent studies have produced conflicting
results. Those findings were reconciled in the first study of the thesis, which showed
that, on false belief tasks, patients have intact first-order ToM, but specific impairments
at the second-order level. This was later confirmed using a 'hints' test of ToM.
The results were contrasted with the case of autism. On a spatial reversal test of
executive function, schizophrenics with behavioural signs made more perseverative
errors than controls. No correlations appeared between ToM and executive function
for any of the schizophrenic symptom groups. This was contrasted with the case of
autism, and it was suggested that schizophrenia involves late-occurring, independent
deficits in separate metarepresentational domains.
It was argued that Frith's model of schizophrenia can be extended to include
impaired representation of own knowledge, explaining the deficient use of context
in the disorder. Some evidence was obtained that patients with primarily behavioural
signs are impaired at naming objects in a picture context; this ability was unrelated
to ToM, consistent with independent deficits in separate metarepresentational
domains. It was suggested that 'weak central coherence' in autism may also reflect
impaired representation of own knowledge, and some evidence was obtained that
(like autistics), symptomatic schizophrenics show facilitation on embedded figures
tests. Schizophrenic patients performed the same as controls, however, on an illusions
task. For patients with behavioural signs, embedded figures accuracy was inversely
related to the ability to name objects in a picture context, and it was argued that this
supported task analyses suggesting a common cognitive process.