The cognitive abnormalities underlying the symptomatology and the disability of patients with schizophrenia.

A variety of cognitive impairments can be observed in patients with schizophrenia, including substantial reductions in the intelligence quotient (IQ). I propose that these impairments can be best understood in terms of the abnormal processes underlying the signs and symptoms manifested by the patient at the time of the cognitive assessment. Negative signs such as poverty of speech are associated with defects of willed action, while positive symptoms such as hallucinations are associated with defects of self-monitoring. Hypotheses about the brain systems underlying these processes can be examined using functional brain imaging.