rception, affect, and motor behavior (Cutting 1985; Neale and Oltmanns 1980). Thought disorder refers to a disturbance of the process of making associations between thoughts. Perceptual disturbances are evinced by hallucinations, which may be visual or tactile but are most commonly auditory, typically as voices commenting or giving instructions. Affect can be flat and expressionless or alternatively it can be inappropriate such as anger without provocation, or laughter at misfortune. Finally, motor disturbances can take the form of bizarre facial grimaces, repeated gesturing, or excited agitation of the body; alternatively unusual postures can be adopted and held, in a state of immobility, for long periods. As noted, not all these behaviors would be found in the same person, although some pattern does emerge: disorganized or hebephrenic schizophrenia is characterized by hallucinations, delusions, and inappropriate affect; catatonic schizophrenia by motor disturbances; and paranoid schizophrenia by delusions of persecution, incorporating `ideas of reference' in which personal significance is continually perceived in the actions of other people. Given this range, it may well be expedient to think of schizophrenia as a group of disorders rather than a single disorder which always manifests' itself in the same fashion. While of uncertain etiology, contemporary theories favor a complex interaction between genetic, neurochemical, and social factors as an explanation for schizophrenia. It is generally accepted that the incidence of schizophrenia is close to 1 per cent in the general population: this sets a baseline against which to compare the rates of schizophrenia in offender populations.Spry (1984) reviews the evidence on the incidence of schizophrenia and crime and notes a division in research findings: with studies of non- disordered offender groups the incidence of schizophrenia is around the 1 per cent mark (although P.J. Taylor's 1986...
