The Differential Ability Scales-Second Edition and Cognitive Profile Variability in Young Children with Autism Spectrum Disorder

Background: There has been longstanding interest in elucidating the relationship between intellectual functioning and autism spectrum disorder (ASD), with particular interest in better understanding whether there is unevenness in the cognitive abilities of children with ASD (Joseph, Tager-Flusberg, & Lord, 2002). The Differential Ability Scales, Second Edition (DAS-II; Elliot, 2007) has been specifically recommended as a measure of cognitive abilities in children with ASD because the subtests' conceptually homogenous clusters allow for a clearer comparison of abilities and there are fewer language demands than with measures such as the Wechsler scales (Saulnier & Ventola, 2012). While the DAS-II holds promise as a useful assessment measure, there have been no published studies to date describing the DAS-II cognitive profiles of young children with ASD.

Objectives: To examine DAS-II cognitive profiles in young children with a diagnosis of ASD.

Methods: A record review was conducted of 145 diagnostic evaluations of children seen through a large outpatient autism center in a metro area. For inclusion in the present study, the evaluation had to include the DAS-II, Lower Early Years core subtests (Verbal Comprehension, Naming Vocabulary, Picture Similarities, and Pattern Construction) and a confirmed ASD diagnosis based on the results of a structured autism diagnostic interview and the Autism Diagnostic Observation Scale. A total of 68 children ranging in age from 36 to 70 months (M=52.9, SD=9.7) met these criteria. Proportions of the sample with Verbal-Nonverbal (V-NV) discrepancies were identified based on the 13-point difference between Verbal and Nonverbal cluster scores required for significance at the .05 level of probability, as specified in the DAS-II normative data tables manual. In addition to V-NV discrepancies, subtest score patterns were examined within each cluster.

Results: Analysis of the V-NV cluster scores resulted in the following categories: 41% exhibited a significant discrepancy in favor of nonverbal abilities (V < NV), 12% exhibited a significant discrepancy in favor of verbal abilities (V > NV), and 47% exhibited no discrepancy (V = NV). Therefore, 53% of children demonstrated a significant discrepancy and the majority of the discrepancies were in the V < NV direction. The frequency of the V-NV discrepancies in this sample was significantly higher than reported for the DAS-II normative sample based on an exact binomial test, p < .001. In addition, a repeated measures ANOVA demonstrated significant unevenness in performance across subtests, F (3, 201) = 12.1, p < .001. The mean score for Verbal Comprehension was significantly lower than for all other subtests.

Conclusions: The present study documented cognitive profile variability on the DAS-II in a clinically referred sample of young children with ASD. The high frequency of uneven cognitive development suggests that the DAS-II may be a useful tool in differentiating patterns of cognitive strengths and weaknesses in ASD. Ultimately, the identification of these specific patterns in cognitive functioning is critical in young children, as it informs educational goals, intervention strategies, and progress monitoring.