Incidence versus Degrees of Rotation on the Minnesota Percepto-Diagnostic Test in Brain-Damaged and Schizophrenic Patients

Abstract
20 brain-damaged and 20 process schizophrenic inpatients, equated for average age and educational level, were administered the Minnesota Percepto-Diagnostic Test and the Vocabulary and Block Design subtests from the WAIS. When the Minnesota was scored for incidence of rotations as well as for total number of degrees of rotation, only the degrees measure discriminated between the two groups. However, when IQ was held constant through the use of partial correlation or the IQ correction procedure presented in the test manual, the degrees measure was no longer discriminating. However, since the degrees measure was superior to the incidence measure, it was suggested that visual-motor design reproduction tests with scoring systems using incidence measures may be under-utilizing the modest discriminating power the rotational error type possesses.