The purpose of this study was to determine whether distinct subgroups of children with learning disabilities could be identified using a single, recently developed instrumentthe Differential Ability Scales (DAS). Ward's method of cluster analysis was used to group 83 school-verified children with learning disabilities from the standardization sample. The following six subgroups were identified: (a) generalized, (b) high functioning, (c) normal, (d) underachievement, (e) borderline, and (f) dyseidetic. Not all subgroups displayed the expected discrepancy between intelligence and achievement associated with the current definitions of I.D. In subsequent discriminant analyses, both achievement and diagnostic subtests were necessary for accuracy in classification. This study provided evidence of the DAS's ability to diagnose the learning disabled differentially and provided distinct profiles for LD subgroups. Administration of the diagnostic subtests along with achievement subtests can provide the clinician with valuable diagnostic information for LD.
When a new psychoeducational instrument appears, a logical question arises: "HOW can this test be used to identify students with learning disabilities?" The Differential Ability Scales (DAS; Elliott, 1990) has recently become available for general use for assessment of children from ages 2% through 17 years. The DAS was constructed to reflect the content and organization of the British Ability Scales (Elliott, Murray, & Pearson, 1979). Because of the broad age range, normative structure, and breadth of content, the DAS should have a variety of applications in school and clinical settings and in research (Elliott, 1990). The DAS differs from other cognitive measures in that (a) the General Conceptual Ability (GCA) score (Composite score) incorporates only subtests that are salient measures of "g" having been found to have substantial loadings on that factor (Elliott, 1990); (b) subtests measuring specific processing skills (diagnostic subtests) are not included in determining the total composite score; and (c) achievement measures are included that were normed on the same standardization sample as the cognitive measures.
The DAS's author indicates that the structure of the instrument provides a sound basis for profile analysis by measuring a wide range of abilities reliably and distinctively. However, the diagnostic usefulness of the DAS has yet to be determined. If distinct profiles for separate learning-disabled subgroups can be identified, the efficacy of the DAS in the diagnostic process will be supported.
As yet there do not appear to be any other studies examining the performance of children with learning disabilities on the DAS. Although research is lacking on the DAS, there has been some relevant research using the British Ability Scales (Elliott et al., 1979).