Monday, December 28, 2009

Dssertation Dish: Woodcock -- Johnson and KABC-profile research

Validation of neuropsychological subtypes of learning disabilities by Hiller, Todd R., Ph.D., Ball State University, 2009 , 99 pages; AAT 3379243

The present study used archival data of individuals given the Woodcock-Johnson Tests of Cognitive Abilities 3 rd Edition and the Woodcock-Johnson Tests of Achievement 3 rd Edition in an effort to define subtypes of LD. The sample included 526 subjects aged 6 years to 18 years old who had a diagnosis of some type of LD. Of these, 22.7% had an additional diagnosis other than LD. It was expected that subtypes similar to Rourke's classification of his nonverbal learning disorder and his basic phonological processing disorder would be found.

Portions of the battery were used in a latent class cluster analysis in order to determine group patterns of strengths and weaknesses. Using the Lo-Mendell-Rubin test, a 3 solution model was selected. These three groups showed no evidence of patterns of strengths and weaknesses. These groups were best described as a high, middle, and low group, in that the high group had scores that were universally larger than scores from the middle group, which had scores that were universally higher than the low group. The rates of individuals with comorbid disorders varied greatly between the clusters. The high group had the lowest comorbidity rates in the study, with only 6.8%. That is compared to 26.4% of the middle group and 44.8% of the low group.

These results suggest that clusters found differ more in severity rather than types of LD. Individuals with LD and comorbid disorders are more likely to have more severe deficits.

Profile analysis of the Kaufman Assessment Battery for Children, Second Edition with African American and Caucasian preschool children by Dale, Brittany Ann, Ph.D., Ball State University, 2009 , 130 pages; AAT 3379238

The purpose of the present study was to determine if African American and Caucasian preschool children displayed similar patterns of performance among the Cattell-Horn-Carroll (CHC) factors measured by the Kaufman Assessment Battery for Children, Second Edition (KABC-II). Specifically, a profile analysis was conducted to determine if African Americans and Caucasians displayed the same patterns of highs and low and scored at the same level on the KABC-II composites and subtests. Forty-nine African American (mean age = 59.14 months) and 49 Caucasian (mean age = 59.39) preschool children from a Midwestern City were included in the study and were matched on age, sex, and level of parental education. Results of a profile analysis found African American and Caucasian preschool children had a similar pattern of highs and lows and performed at the same level on the CHC broad abilities as measured by the KABC-II. Comparison of the overall mean IQ indicated no significant differences between the two groups. The overall mean difference between groups was 1.47 points, the smallest gap seen in the literature. This finding was inconsistent with previous research indicating a one standard deviation difference in IQ between African Americans and Caucasians. A profile analysis of the KABC-II subtests found the African American and Caucasian groups performed at an overall similar level, but did not show the same pattern of highs and lows. Specifically, Caucasians scored significantly higher than African Americans on the Expressive Vocabulary subtest which measures the CHC narrow ability of Lexical Knowledge.

Results of this study supported the KABC-II's authors' recommendation to make interpretations at the composite level. When developing hypotheses of an individual's strengths and weaknesses in narrow abilities, clinicians should be cautious when interpreting the Expressive Vocabulary subtest with African Americans. Overall, results of this study supported the use of the KABC-II with African American preschool children. When making assessment decisions, clinicians can be more confident in an unbiased assessment with the KABC-II.

Future research could further explore the CHC narrow abilities in ethnically diverse populations. Additionally, more research should be conducted with other measures of cognitive ability designed to adhere to the CHC theory, and the appropriateness of those tests with an African American population. Furthermore, future research with the KABC-II could determine if the results of the present study were replicated in other age groups.

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