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Differential Ability Scales - Second Edition (DAS-II)

The Differential Ability Scales – Second Edition (DAS-II; Elliott, 2007) is an individually administered norm-referenced battery of cognitive subtests for children and adolescents ages 2–6 through 17–11.

Overview

Although most cognitive measures are not truly language-free, the DAS-II controls for language loading by providing a special Nonverbal Index and can be used easily with very young children and English Language Learners. It consists of two overlapping batteries, the Early Years Battery and the School-Age Battery. Several subtests within each battery can be used out of level for individuals working above or below typical levels by age.

The DAS-II yields (a) a composite score focused on reasoning and conceptual abilities, the General Conceptual Ability (GCA) score; (b) lower-level composite scores called cluster scores; and (c) diverse, specific-ability measures, including the core subtests, which comprise the GCA and diagnostic subtests. Verbal Ability measures the child’s acquired verbal concepts and knowledge. Nonverbal Ability represents complex, nonverbal, inductive reasoning requiring mental processing. Spatial Ability measures complex visual processing. Diagnostic Clusters include Working Memory, Processing Speed, and School Readiness. The DAS-II yields t-scores for subtests and standard scores and percentiles for cluster and index scores and the GCA.

Summary

Author (yr) Age Range (yrs) Method of Administration/Format Approx. Time to Administer Subscales
Differential Ability Scales – Second Edition (DAS-II) Elliott (2007) 2.5–18

Individually administered, norm-referenced measure of cognitive abilities; aligned to the Cattell-Horn-Carroll (CHC) model; 20 subtests (core and diagnostic) in two overlapping batteries: Early Years (2–6 to 3–5 or 3–6 to 6–11) and School-Aged (0–7 to 11–17)

Yields t-scores and percentiles by age; t- scores convert to standard scores for the cluster and composite scores and for GCA
60-90 min.

2–6 to 3–5 yrs.: General Conceptual Ability (GCA) score, Verbal Ability and Nonverbal Ability cluster scores (considered Core Clusters); 3–6 to 11–17: General Conceptual Ability (GCA) score; Verbal Ability, Nonverbal Reasoning Ability, and Spatial Ability cluster scores (Core Clusters); Special Nonverbal Composite; Diagnostic cluster scores (0–5 to 11–17 years) – Working Memory and Processing Speed (0–5 to 8–11 years); School Readiness Cluster

Availability: Pearson Assessment http://bit.ly/1EMmer5

Misconceptions

Myth Reality
Full-scale IQ is a good description of a student’s cognitive ability. Students with autism typically demonstrate a scattered profile on comprehensive cognitive measures, performing better on tasks involving rote skills than on tasks involving problem solving, conceptual thinking, and social knowledge (Mayes & Calhoun, 2008; Meyer, 2001-2002).
If a student has an average IQ, an adaptive behavior measure is unnecessary. Although a student has an average IQ and may even be doing well academically, it does not mean that an adaptive measure is not necessary. Research indicates that many students with autism have deficits in communication, daily living skills, and socialization (Lee & Park, 2007; Myles et al., 2007). Klin and Volkmar (2000) stated that adaptive behavior is a critical area of planning for students with Asperger Syndrome (now referred to as autism spectrum disorder, Level 1) to facilitate transition from the school environment to work and community environments.
If a student demonstrates a well-below-average IQ, the student does not have any cognitive skills. A flat profile of skills may indicate difficulty accessing what the student knows. Formal cognitive assessments may not yield valuable information for assessing current level of functioning and needs for programming. In addition, students with autism spectrum disorder may not be able to generalize skills from the classroom setting to the testing environment, or the manner in which the information is being assessed may prohibit the child from demonstrating mastery of skills. For example, if the student has learned to perform a task in one way with a certain prompt and the assessment asks for it in a different way, the student may not be able to demonstrate knowledge of the skill.
Formal IQ is more valid than informal data from the classroom. Informal classroom data provide information about how the student functions on a daily basis. Analyzing formal and informal data to determine patterns of skills and learning is a key component of assessment (Hagiwara, 2001-2002). Informal data from the classroom may be more valuable than information gathered in a contrived one-on-one setting when determining programming for a student with autism spectrum disorder.

Research

Author (yr) Sample Size Topic(s) Addressed Outcome
Kuriakose (2014) 23 Convergent validity

*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.

*From abstract
Author (yr) Sample Size Topic(s) Addressed Outcome
Kuriakose (2014) Farmer, Golden, & Thurm (2015) 118 with autism spectrum disorder (ASD), non-ASD developmental delays, and typically developing children Convergent Validity

*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.
*From abstract