Overview
The Differential Ability Scales – Second Edition (DAS-II; Elliott, 2007) is an individually administered, norm-referenced instrument that assesses the cognitive abilities of children and adolescents ages 2 years, 6 months through 17 years, 11 months. The DAS-II is useful for identifying strengths and weaknesses so appropriate individual education program (IEP) goals, intervention strategies, and progress monitoring can be developed; and comparing ability scores over time, even when normative scores cannot be obtained. This test predicts academic achievement on the basis of ability equally well for African American, Asian American, Hispanic/Latino, and White/non-Hispanic children. It consists of two batteries, the Early Years Battery and the School-Age Battery, which were normed for overlapping age ranges to increase the usefulness for children of varying ability levels. Notably, the core battery for ages 2:6-3:5 contains only four subtests and may be more useful as a screening instrument for children of this age. Instructions are provided in both English and Spanish for the nonverbal subtests.
The DAS-II is aligned with Cattell-Horn-Carroll cognitive theory. In addition to an overall composite , the General Conceptual Ability (GCA) score, this instrument also yields a Special Nonverbal Composite (SNC) score for children who may have difficulty with oral language. Cluster scores that comprise the GCA include Verbal Ability, Nonverbal Reasoning Ability, and Spatial Ability (ages 3:6-17:11 only). These cluster scores consist of six core subtests (or four, for children 2:6-3:5) that are designed to measure verbal, nonverbal, and spatial reasoning. In addition to the core subtests, ten diagnostic subtests are available to measure verbal and visual working memory, immediate and delayed recall, visual recognition and matching, processing and naming speed, phonological processing, and understanding of basic number concepts. The DAS-II can be scored manually or with the Scoring Assistant software included in every kit.
Summary
Age: 2 years 6 months to 17 years 11 months
Time to Administer: Core battery: 45-60 minutes; Diagnostic subtests: 30 minutes
Method of Administration: Individually administered, norm-referenced measure of cognitive abilities; aligned to the Cattell-Horn-Carroll (CHC) model two overlapping batteries: Early Years (2:6-6:11) and School-Aged (7:0-17:11)
Yields standard scores (M = 100, SD = 15) for composite and cluster scores, T-scores (M = 50, SD = 10) for subtest scores, percentile ranks, confidence intervals, qualitative descriptors, and age equivalents.
Subscales: Overall Composite Scores: General Conceptual Ability (GCA) score; Special Nonverbal Composite (SNC) score
Cluster Scores: Verbal Ability Cluster; Nonverbal Reasoning Ability Cluster; Spatial Ability Cluster
Autism Related Research
Bishop, Farmer, & Thurm (2015)
Age Range: First assessment age 2 years, with re-assessment at age 3, 5, 9, and 19 years
Sample Size: 84 with ASD
Topics Addressed:
Correspondence between cognitive ability in early childhood and adulthood
Outcome:Bishop, Farmer, & Thurm (2015)
This longitudinal study results indicated that nonverbal cognitive scores (NVIQ) in individuals with ASD declined between toddlerhood and adulthood, particularly among those whose scores were below 70. However, NVIQ was generally stable for the majority of individuals with ASD whose cognitive ability was in the average range. Clinicians should communicate carefully regarding prognosis of cognitive ability to parents of young children with ASD.
Farmer, Golden, & Thurm (2015)
Age Range: Age Range (in years as given in study) 2–10 years
Sample Size: 47 with autism spectrum disorder (ASD); 28 with non-ASD developmental delays; 43 typically developing children
Topics Addressed:
Concurrent validity between DAS-II and MSEL
Outcome:Farmer, Golden, & Thurm (2015)
Compared DAS II with Mullen Scales of Early Learning (MSEL). Scores on the DAS-II and MSEL were highly correlated, suggesting that they measure a similar construct. However, curve estimation revealed large mean differences in scores that varied as a function of the child's cognitive ability level.
The authors concluded that interchanging MSEL and DAS-II scores in research studies without regard to the discrepancy in scores may produce misleading results in both cross-sectional and longitudinal studies of children with and without ASD, and, thus, this practice should be implemented with caution.
Kuriakose (2014)
Age Range: 7–15 years
Sample Size: 23 with ASD
Topics Addressed:
Convergent validity of WISC-IV and DAS-II
Outcome:Kuriakose (2014)
Participants achieved significantly higher overall scores on the DAS-II and nearly half the sample achieved a higher classification label on the DAS-II. The difference between overall scores is suggested to be attributable to a relative weakness in processing speed, which is assessed on the WISC-IV but not the DAS-II. Autistic symptomatology was not associated with cognitive scores, while adaptive behavior was positively associated. Neither was associated with the magnitude of difference between overall scores. Choice of assessment should be considered carefully given the systematic differences in overall scores produced in this population.