Diagnostic Utility of the WISC-III Developmental Index as a Predictor of Learning Disabilities

Abstract

Wechsler's Deterioration Index (WDI) was developed as an indicator of cognitive impairment in adults but has been applied to children, because neuropsychological deficits have often been hypothesized to account for learning difficulties during the development period. Renamed the Wechsler Developmental Index, this measure has been used to discriminate among groups of children with and without learning disabilities. The present study replicated those findings with the Wechsler Intelligence Scale for Children-Third Edition, but also applied more appropriate diagnostic efficiency statistics to analyze the actual diagnostic utility of the WDI. These analyses revealed that the WDI performed at chance levels when distinguishing 611 students diagnosed with learning disabilities from those diagnosed with emotional disabled (n = 80) or mental retardation (n = 33), as well as from 2,200 simulated random nondisabled cases. It was concluded that mean group differences were not adequate and that ipsative indicators must be definitively validated in experimental environments before they can be applied in practice.

Incremental validity of WISC–III profile elevation, scatter, and shape information for predicting reading and math achievement.

“…1984;Kline et aI., 1993;Kramer et aI., 1987;McDermott, Fantuzzo, & Glutting, 1990;McDermott, Fantuzzo, Glutting, Watkins. & Baggaley, 1992;Watkins, 1996;Watkins & Kush. 1994: Watkins, Kush, & Glutting, 1997a, 1997b, suggests that using WISC-fII suhtest scatter and shape to predict academic performance or differential diagnosis is a decision to act in opposition to the scienti!ic evidence, In contrast, a mcasnre of cognitive elevation was the most parsimonious predictor uf reading and math achievement among both exceptional and nonexceptional studcnts in this study and is supported by a robust scientific literature (Neisser ct a1.. 1996), Thus, use of global intellectual indices would renect a decision to act in accordance with the scientific evidence,…”

Diagnostic Utility of WISC-III Subtest Variability among Students with Learning Disabilities

“…ROC analyses indicated that subtest variability is a useless indicator of learning disability status across the full range of possible cut scores (i.e., prevalence levels). The WISC-III developmental index, ACID profile, and SCAD profile have also proven to have little or no diagnostic utility in identifying exceptional children (Watkins, 1996;Watkins, Kush, & Glutting, 1997a, 1997b. When considered within the broader, and generally negative, context of subtest profile research (Kavale & Forness, 1984;Kramer, Henning-Stout, Ullman, & Schnellenberg, 1987;McDermott, Fantuzzo, & Glutting, 1990;McDermott, Fantuzzo, Glutting, Watkins, & Baggaley, 1992;Mueller, Dennis, & Short, 1986;Watkins & Kush, 1994), subtest variability is unsupported as a tool in the diagnosis of learning disabilities.…”

Discriminant and predictive validity of the WISC-III ACID profile among children with learning disabilities

“…McDermott, Fantuzzo, and Glutting (1990) reached similar conclusions regarding Wechsler subtest profile analysis and recommended that psychologists "just say no" (p. 299) to this practice. Recent empirical investigations have failed to provide support for several WISC-III subtest profiles (Daley & Nagle, 1996;Dumont & Willis, 1995;Gussin & Javorsky, 1995;Ward et al, 1995;Watkins, 1996;Watkins, Kush, & Glutting, to appear). This evidence, both historic and current, suggests that WISC-III subtest analysis should be abandoned.…”