From its initial labelling as dementia praecox, the disorder we now ca
ll schizophrenia has always been associated with cognitive impairments
. While there was a time when these deficits were believed to be secon
dary to treatment and institutionalisation, there is now overwhelming
evidence that cognitive impairments are an essential feature of schizo
phrenia. Precise specification of the form of these impairments has im
portant implications for the nature of the underlying brain malfunctio
n.