THE DEVELOPMENTAL RELATIONSHIP BETWEEN NEUROPSYCHOLOGICAL AND ACHIEVEMENT VARIABLES: A CLUSTER ANALYTIC STUDY

Current discussions of specific reading disabilities increasingly mention the heterogeneity of this population and the need for ways to delineate meaningful subgroups. This study attempted to respond to this need by developing a multivariate classification system based on neuropsychological subskills which was then related to achievement measures. A unique characteristic of this study is its longitudinal approach. Furthermore, the classification system is based on the performance of children from all skill levels in order to verify that specific deficits are unique to single categories of achievers.;Data were collected from 211 boys first during their kindergarten year of school. They were then re-evaluated twice on the same measures at subsequent 3-year periods; the entire study spanned 6 years. The basic test measures at each probe included the Developmental Test of Visual-Motor Integration. The Recognition-Discrimination Test, the Embedded Figures Test, Peabody Picture Vocabulary Test raw score, WPPSI/WISC Similarities, the Verbal Fluency Test, and the Dichotic Listening Test (total recall). From an independent factor analysis of the Satz Predictive Battery these measures were found to be factor-pure and strong contributors to particular factors. They are also untroubled by floor and ceiling effects. Consequently, they were combined into spatial-perceptual and conceptual-linguistic factor scores at each of the three probes. These neuropsychological factor scores were then submitted to a cluster analytic procedure which resulted in 12 distinctive patterns of performance. Internal and external validity were verified through a series of statistical procedures.;Results confirmed a direct relationship between neuropsychological subgroups and achievement. Subgroups with the best neuropsychological performance were also the best achievers, just as those most deficient neuropsychologially were also the lowest achievers. Examining the impact of each factor type, however, revealed much more complex relationships. One subgroup with a specific perceptual deficit had a very low achievement. Another subgroup deficient only in verbal skills had low reading and spelling scores and average arithmetic skills. At the opposite end of the continuum, subgroups with relative strengths in either perceptual or verbal skills had very superior achievement scores. For all levels of skills, however, the impact on achievement is greatest when neuropsychological skills are equivalent.;Clear developmental changes were evident in three subgroups. For two subgroups the changes were regressive. The third subgroup showed consistent improvement in neuropsychological subskills. For these subgroups, the eventual level of performance, rather than the developmental patterns, seemed most clearly related to achievement competency.;A trend was apparent for a relationship between perceptual skills and arithmetic achievement. From other analyses, it was determined that the subgroups which were lowest on neuropsychological skills were also rated as having lower socioeconomic backgrounds and as having more frequent positive neurological findings. In addition, the mothers of these children were also the poorest readers. No significant relationship was found between fathers' reading scores and the subgroups.;The results of this study underscore the benefits from examining children within the context of a carefully generated classification system. Evidence contrary to unitary deficit models was discussed, as were implications for future research.