Differential Ability Scales (DAS)

The Differential Ability Scales (DAS; Elliott, 1990a) is an individually administered battery of cognitive and achievement tests for children and adolescents aged 2 years, 6 months through 17 years, 11 months. Because the DAS covers such a wide age range, it is divided into three levels: Lower Preschool (ages 2 years, 6 months through 3 years, 5 months), Upper Preschool (aged 3 years, 6 months through 5 years, 11 months), and School-Age (6 years, 0 months through 17 years, 11 months). The DAS was designed to measure specific, definable abilities and to provide interpretable profiles of strengths and weaknesses. The DAS also contains three achievement tests, co-normed with the cognitive battery, which allows direct ability-achievement discrepancy analysis. The DAS is considered suitable for use in any setting in which the cognitive abilities of children and adolescents are to be evaluated, although many of the DAS subtests are not appropriate for students with severe sensory or motor disabilities. The DAS cognitive battery yields a composite score labeled General Conceptual Ability (GCA) that is defined as "the general ability of an individual to perform complex mental processing that involves conceptualization and transformation of information" (Elliott, 1990b, p. 20).

The DAS contains a total of 20 subtests grouped into Core Cognitive, Diagnostic, or Achievement tests. The Core Cognitive subtests are those used to compute the GCA and cluster scores, while the Diagnostic subtests are those considered important and useful in the interpretation of an individual's strengths and weaknesses, but which do not assess "complex mental processing" well. The Diagnostic subtests provide useful information without contaminating the GCA with subtests showing low g loadings. The Lower Preschool battery consists of four core subtests that combine to yield the GCA and two diagnostic subtests that may be administered. The Upper Preschool battery includes six core subtests and an additional five diagnostic subtests. The School-Age battery includes six core subtests and three additional diagnostic subtests. For the Upper Preschool and the School-Age batteries, the subtests not only combine to produce the GCA but also yield two or three cluster scores. For Upper Preschool children, these cluster scores represent Verbal and Nonverbal abilities. For School-Age children, the cluster scores represent Verbal, Nonverbal Reasoning [fluid reasoning (Keith et al., 1990)], and Spatial abilities. Although the "typical" Preschool battery is given to children aged 3 years, 6 months through 5 years, 11 months and the "typical" School-Age battery to children 6 years, 0 months through 17 years, 11 months, the Preschool and School-Age batteries were also normed for an overlapping age range (5 years 0 months through 6 years 11 months). This overlap provides the examiner flexibility when testing bright, younger children or less able, older children. In these cases, subtests appropriate for the individual's abilities are available. Examiners may choose to give either battery or one battery and additional subtests from the other to children in the overlapping age range. Exhibit-1 describes the subtests of the DAS.

• Verbal Comprehension: following oral instructions to point to or move pictures and toys.
• Naming Vocabulary: naming pictures.
• Word Definitions: explaining the meaning of each word. Words are spoken by the evaluator.
• Similarities: explaining how three things or concepts go together, what they all are (e.g., house, tent, igloo; love, hate, fear)

• Block Building: imitating constructions made by the examiner with wooden blocks.
• Picture Similarities: multiple-choice matching of pictures on the basis of relationships, both concrete (e.g., two round things among other shapes) and abstract (e.g., map with globe from among other round things).
• Copying: drawing pencil copies of abstract, geometric designs.
• Recall of Designs: drawing pencil copies of abstract, geometric designs from memory after a 5-second view of each design.
• Pattern Construction: copying geometric designs with colored tiles or patterned cubes. There are time limits and bonus points for fast work. An alternative "untimed" procedure uses time limits, but no speed bonuses.

• Matrices: solving visual puzzles by choosing the correct picture or design to complete a logical pattern.
• Sequential and Quantitative Reasoning: figuring out the mathematical relationship that relates the numbers in each of two pairs of numbers and applying that rule to another number to complete the third pair.

• Early Number Concepts: oral math questions with illustrations – counting, number concepts, and simple arithmetic.

• Basic Number Skills: paper-and-pencil math computation.
• Spelling: written spelling of dictated words, like a school spelling test.
• Word Reading: accuracy of reading increasingly difficult words aloud from a list.

• Matching Letter-Like Forms: multiple-choice matching of shapes that are similar to letters.
• Recall of Digits: repeating increasingly long series of digits dictated at two digits per second.
• Recognition of Pictures: seeing one, two, or three pictures for five seconds or four pictures for ten seconds and then trying to find those pictures within a group of four to seven similar pictures.
• Recall of Objects-Immediate: viewing a page of 20 pictures, hearing them named by the evaluator, trying to name the pictures from memory, seeing them again, trying again to name all the pictures, and repeating the process once more. The score is the total of all the pictures recalled on each of the three trials, including pictures recalled two or three times.
• Recall of Objects-Delayed: trying to recall the pictures again on a surprise retest 15 to 20 minutes later.
• Speed of Information Processing: the student scans rows of figures or numbers and marks the figure with the most parts or the greatest number in each row. The score is based on speed. Accuracy does not count unless it is very poor.