Psychological Assessment Versus Psychological Testing: Validation From Binet to the School, Clinic, and Courtroom

Increasingly, psychological assessment is conducted with clients and patients involved in child custody and personal injury litigation. Clinical neuropsychologists are being asked sophisticated questions by attorneys regarding the validity of practitioners' most highly respected tests. Research reviewed here bears on the validity of test-buttressed clinical opinions, including research related to the following psychometric properties of individual test scores: standard errors of measurement, test-retest stability and subtest-to-subtest intercorrelations. The highest and the lowest subtest scores used as indices, respectively, of an individual's premorbid level of cognitive functioning and the degree of current impairment from that presumed earlier level is not justified when used in isolation from the life history and current medical findings. Although many practitioners use information from the wider research, courtroom experience suggests that a number do not; contrariwise, the attempt of Faust and Ziskin (1988a) to undermine the courtroom testimony of every psychologist who serves as an expert witness is also criticized.