title: Strategies for resolving the heterogeneity of schizophrenics and their relatives using cognitive measures.
abstract: The resolution of the heterogeneity of schizophrenics and their relatives using cognitive tasks requires measures of individual differences--usually of differential ability, which is inferred from differential performance. Tasks that are suited for establishing a group's differential ability are often unsuited for measuring individual differences. The problem is that for any group for which Tasks A and B have different mean accuracy, the (A - B) difference scores of individual subjects have an artifactual curvilinear relation to (A + B) overall accuracy, with the largest (A - B) scores occurring at about 50% (A + B) overall accuracy for a dichotomously scored free-response task. Two possible solutions are (a) to convert Task B scores to residualized scores, using the regression of Task B scores on Task A scores as determined for normal subjects; or (b) to titrate overall (A + B) accuracy of each subject to a constant level by manipulating a variable.
authors.forename: L J
authors.initials: LJ
authors.lastname: Chapman
authors.forename: J P
authors.initials: JP
authors.lastname: Chapman
mesh_terms: D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis*; D006801:Humans; D011594:Psychometrics; D012565:Schizophrenic Psychology; D013223:Statistics as Topic