In Reply.—
We thank Dr Cleghorn and his colleagues for their interest in our study1 and for their comments. Regional cerebral blood flow values for the two individual right parietal detectors 6 and 8 to which Cleghorn et al refer are presented in Table 1. There were no significant differences between 25 normal control subjects and 24 patients with schizophrenia who were not receiving medication during either Raven's Progressive Matrices or the symbols matching control task described in our article. The groups also did not differ in the degree of change between the two tasks. Examination of the values in Table 1 may appear to show that the patients have lower values, but none of these small differences approached significance, despite the use of statistically liberal multiple t tests. Furthermore, these regional values must be considered in the context of slightly but not significantly lower flow in all brain