It has been reported that schizophrenic individuals tend to exhibit a deficit in abstract concept formation as measured on the Category Test (CT) or the Wisconsin Card Sorting Test (WCST; Heaton, Baade, & Johnson,1978; Morice, 1990; Wright, 1975). When responding to the WCST, regional cerebral blood flow (rCBF) significantly distinguished schizophrenic individuals from controls (Weinberger, Herman, & Zee, 1986). Normals showed an increase of rCBF in the dorsolateral prefrontal cortex (DLPFC) whereas schizophrenics showed none. Liddle and Morris (1991) reported that frontal lobe impairment correlated with severity of psychomotor poverty and disorganisation. Crow (1980) reported that individuals with Type I (positive) symptoms exhibited significantly less intellectual impairment as compared with patients with Type II (negative) symptoms (cf. Hoff, Riordan, O'Donnell, Morris, & DeLisi, 1992). Weinberger (1987) suggested that negative symptoms may be related to frontal lobe dysfunction, particularly in the DLPFC.
The Booklet Category Test (BCT; DeFilippis & McCampbell, 1979) measures abstract concept formation (Boyle, 1988a, 1988b; Hammeke, 1985;Heaton & Pendleton, 1981). Based on attempts at shortening the CT (Boyle, 1975, 1986), an abbreviated BCT would seem suitable for use with schizophrenic patients (cf. Reitan & Davidson, 1974). Russell and Levy (1987) also devised a short-form comprising 95 items. In the present study, their procedure is used to shorten the BCT.
The purpose of this study is to examine abstract concept formation in schizophrenics, in relation to the presence or absence of delusional symptoms. It is hypothesized that there is a continuum of deficits on the BCT going from controls, to recently delusional schizophrenic individuals, to schizophrenic patients with negative symptoms, with the deficit on the BCT increasing across the three groups respectively.