MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS 11: 197 208 (2005) GENERAL MEASURES OF COGNITION FOR THE PRESCHOOL CHILD Elizabeth O. Lichtenberger* Alliant International University, San Diego, CA Preschool-age children who are experiencing delays in physical, cognitive, communication, social, emotional, or adaptive development are often referred for a comprehensive assessment to make diagnostic determinations and to help develop appropriate interventions. Typically cognitive assessment has a key role in a comprehensive evaluation of a young child. In this article, five individually administered tests of cognitive ability, normed for the preschool-age child, are reviewed. These specific tests include the Bayley Scales of Infant Development, 2nd edition, the Kaufman Assessment Battery for Children, 2nd edition, the Wechsler Preschool and Primary Scale of Intelligence, 3rd edition, the Stanford-Binet Intelligence Scale, 5th edition, and the Differential Abilities Scales. The following is provided for these cognitive instruments: a description of the test procedures, information on scoring systems, highlights of the technical qualities, and a summary of the general meaning of test results. The article concludes with strengths and limitations of the instruments. 2005 Wiley-Liss, Inc. MRDD Research Reviews 2005;11:197 208. Key Words: preschool; cognitive assessment; KABC-II; BSID-II; WPPSI-III; SB5; DAS Preschool assessment takes places for many reasons: screening, diagnosis, placement decisions, and remediation of problems. Research has shown that early intervention in a child s life is necessary to minimize lasting effects of a child s difficulties [Kenny and Culbertson, 1993]. Thus, a comprehensive cognitive assessment in the preschool years can be a key component of a thorough multidisciplinary evaluation that directly leads to intervention strategies. A broad range of assessment measures should be used to gain a full understanding of a preschooler s functioning (e.g., parent and teacher reports, behavioral observation, detailed developmental history, and play-based assessment, in addition to traditional cognitive tests). This article focuses on the traditional tests of cognitive ability, although they are by no means the only true measure of a child s development. There are many measures of cognitive ability for the preschool child some are comprehensive measures that attempt to assess many facets of general cognitive ability and some are more specialized instruments that target a selective number of cognitive abilities. Yet others have been designed as brief instruments that can be used as a screening tool in the assessment of preschooler s cognitive ability. Comprehensive measures of cognitive ability are useful in assessing young children with developmental disabilities, because these measures yield information about multiple domains of functioning that are comparable with one another (intraindividual differences) as well as to a normative group of typically developing children (interindividual differences). The difficulty with many comprehensive cognitive measures is that they often do not permit the estimation of functioning of children at extremely low levels (e.g., below an intelligence quotient (IQ) of 40 50 or more than 3 SD below the mean). This article reviews and compares five tests of general cognitive ability for the preschool child that are comprehensive in scope and that are widely known in the fields of psychology, school psychology, and neuropsychology: Bayley Scales of Infant Development, 2nd edition (BSID-II; [Bayley, 1993]), Kaufman Assessment Battery for Children, 2nd edition (KABC-II; [Kaufman and Kaufman, 2004a]), Wechsler Preschool and Primary Scale of Intelligence, 3rd edition (WPPSI-III; [The Psychological Corporation, 2002]), Stanford-Binet Intelligence Scale, 5th edition (SB5; [Roid, 2003]), and the Differential Abilities Scales (DAS; [Elliott, 1990a,b]). For each test, a general description is provided, as well as brief information on its historical, conceptual, and theoretical background; the scoring systems and the technical qualities of the tests are summarized; interpretation is briefly discussed to give readers a basic understanding of the meaning of cognitive test results. Detailed information on how to interpret these measures is beyond the scope of this article; however, appropriate references are suggested with each test for readers interested in more in-depth interpretive information. Each test has areas that need improvement or that warrant caution on the examiner s part, and each test also has unique qualities that make it especially useful as a diagnostic tool. Thus, the strengths and weaknesses of the instruments are highlighted to provide readers with an understanding of advantages and disadvantages in administering these particular instruments. GENERAL INFORMATION ABOUT THE TESTS The five individually administered tests of general cognition for the preschool child described in this article vary in terms of the age range that they assess, their technical qualities, and the specific cognitive domains that they measure. In Table 1, information is provided about age range that the tests cover and the tests administration time, in addition to the tests authors, publishers, publication dates. Examiners should be aware that *Correspondence to: Elizabeth O. Lichtenberger, Ph.D. E-mail: drlichtenberger@aol.com Received 11 July 2005; Accepted 12 July 2005 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/mrdd.20076 2005 Wiley-Liss, Inc.
Table 1. General Information About the Five Measures of Cognition for Preschool Children Test Author Year of Publication Publisher Age Range that Test Assesses Time to Administer Bayley Scales of Infant Development, 2nd edition (BSID-II) Bayley 1993 The Psychological Corporation 1to42mo. 25 60 min (for 16 mo.) 25 35 min (for 15 mo.) The Kaufman Assessment Battery for Children, 2nd edition (KABC-II) The Wechsler Preschool and Primary Scale of Intelligence, 3rd Edition (WPPSI-III) Stanford-Binet Intelligence Scale, 5th edition (SB5) The Differential Abilities Scales (DAS) Kaufman and Kaufman The Psychological Corporation 2004 American Guidance Service 2002 The Psychological Corporation 3 0 to 18 11 23 35 min (for age 3) 30 45 min (for age 4) a 35 50 (for age 5) a 2 6 to 7 3 30 45 min (for age 4 0) 45 60 min (for age 4 0) Roid 2003 Riverside 2 to 85 45 75 min (for Full Scale IQ) 15 20 min (for abbreviated battery IQ) Elliott 1990 The Psychological 2 6 to 17 11 25 65 min b Corporation a When administering Supplementary subtests in addition to Core KABC-II subtests, the battery can take up 60 min for 4-year-old children and 90 min for 5-year-old children. b Save (2003) reported that the DAS lower preschool level will take about 40 min and the upper preschool level will take about 90 min to administer. newer test norms are generally preferable to older norms. Flynn [1987] has demonstrated that norms in the United States become outdated by about 3 points/decade. Thus, tests such as the BSID-II and DAS that were published more than 10 years ago, will produce scores that may be inflated by three or more points. When choosing a general cognitive test to administer to young children with developmental disabilities, administration time needs to be carefully considered. Often such children will have difficulty maintaining focused attention for a long period of time, and thus tests with shorter administration times are more beneficial. All tests will offer natural breaks between subtests, so if a child is beginning to lose motivation, interest, or focus, examiners may choose to then temporarily suspend the testing for a short play break or snack, and resume when the child seems ready to focus. Even with the most challenging preschool children try to avoid stopping midway through a subtest. Tangible or social rewards can be used to encourage children to complete the tasks at hand, although they should be used judiciously. In addition to considering administration time, examine the age range that the test is designed to measure to determine whether it will be able to adequately measure a child s abilities. As children with developmental disabilities often are performing at levels that are well below that of their peers, choose instruments that will have an adequate range of content to assess a child at their current level of ability. For example, if a 5-year-old child is functioning at least 2 years below his chronological age, make sure that the test you administer has a floor appropriate for a 3-year-old. A test with an adequate floor will yield a standard score 2 standard deviations (SDs) or more below the mean (a standard score of 70 or below). If a test does not have an adequate floor, then it may not accurately identify children with very delayed functioning [Bracken, 2000]. Description of Scoring Systems Each of the tests discussed in this article yields raw scores that are converted in to standard scores (i.e., norm referenced scores). For the global scales (e.g., IQs or Indexes) the M 100 and the SD 15. Scaled scores are calculated for the tests subtests with a M 10 and asd 3. The scoring for the DAS is slightly different than the other tests mentioned in that raw scores are converted to ability scores, which take into account both the difficulty of the items and the number of items answered correctly. However, DAS ability scores are not norm-referenced. Therefore, the DAS ability scores for cognitive subtests must then be converted to T-scores (M 50, SD 10) in order to make comparisons with other children or between subtests. T-scores are then summed and converted to a standard score (M 100, SD 15) for both cluster scores and the General Conceptual Ability. Percentile ranks, confidence intervals, age equivalents, and descriptive categories are also available scoring metrics for all of the instruments. Description of Psychometric Properties The psychometric characteristics of a test give information about its technical adequacy. How well a test is standardized provides information about the quality of the sample from which the norms were developed. Each of the five instruments discussed in this article was standardized with a large, well-stratified sample (ranging from 1,700 to nearly 5,000 participants). The samples were chosen to match closely the U.S. Census data on the variables of age, gender, geographic region, ethnicity, and parental education (see Table 2). Other key technical qualities to consider about a test are its reliability and validity. Saye [2003] stated that the typical standard for internal consistency and stability of a measure s total test score is 0.90; and is 0.80 for composites and subtests. As noted in Table 2; the reliability of each of these tests (the stability of the test score over time) is strong. The validity (how well a test measures what it purports to measure) of a test is typically demonstrated with factor analysis (construct validity); correlations with other measures of cognitive ability (concurrent validity); or correlations with measures administered at a later time (predictive validity). Predictive validity is normally weak for tests of preschoolers cognitive ability because their development occurs so rapidly and because test items may measure different constructs at different ages [Bracken, 2000; Saye, 2003]. Table 2 also summarizes the evidence of each tests validity. 198 MRDD RESEARCH REVIEWS MEASURES OF COGNITION FOR PRESCHOOL LICHTENBERGER
Table 2. Standardization and Psychometric Properties of Five Preschool Tests Test Standardization Sample Evidence of Reliability Evidence of Validity BSID-II 1,700 children, including 100 children (50 boys and 50 girls), in each of the 17 age groups between 1 month and 42 months of age KABC-II 3,025 children, divided into 18 age groups, with each of the 6 age groups from ages 3 to 6 composed of 100 200 children WPPSI-III 1,700 children, divided into 9 age groups, each composed of 200 children, except for the 7 0 to 7 3 age group that was composed of 100 children SB5 DAS 4,800 participants, including 1,400 children ages 2 5. 3,475 children and adolescents with 175 children for each age group from 2 6 to 4 11, and 200 children/year for ages 5 0 17 11 Internal-consistency reliability coefficients: Mental Scale (M 0.88; range 0.78 0.93) Motor Scale (M 0.84; range 0.75 0.87) Behavior Rating Scale Total Score (M 0.88; range 0.82 0.92) Internal-consistency coefficients for ages 3 6: 0.95 for the MPI 0.96 for the FCI Range for individual subtests 0.69 for Hand Movements to 0.92 on Rebus Subtests Mdn 0.84 Internal-consistency coefficients: 0.95 for V-IQ 0.93 for P-IQ 0.89 for PSQ 0.93 for GLC 0.96 for FS-IQ Range for subtests across all ages: 0.75 for Block Design (for the 4 0 to 4 5 age group) to 0.96 on Similarities (for ages 4 6 to 4 11 and 5 6 to 5 11) Subtest Mdn 0.88 Test-retest coefficients: 0.91, 0.86, and 0.92 for the V-, P-, and FS-IQ, respectively Internal-consistency coefficients: 0.98 for FS IQ 0.95 for Nonverbal IQ 0.96 for V-IQ Nonverbal subtests ranged from 0.85 to 0.89 Verbal subtests ranged from 0.84 to 0.89 Indexes ranged from 0.90 for Fluid Reasoning to 0.92 for Knowledge, Quantitative Reasoning, and Visual-Spatial Processing Test-retest reliability (for 2 5 years): 0.92 to 0.95 for the IQs 0.82 to 0.92 for the Factor Index Scores 0.76 to 0.91 for the subtest scores Internal-consistency coefficients (for the preschool age group): Subtests range from 0.68 for Block Building (at age 2 6) to 0.90 for Pattern Construction (at age 5 years) Generally in the low 0.80s, but the GCA score has higher reliability coefficients (about 0.90) Test-retest reliability: GCA 0.90 Criterion validity is supported by correlations between the BSID-II MDI and the WPPSI-R (0.73), and the Mc- Carthy Scales of Children s Abilities (0.79) Results of an exploratory factor analysis support the construct validity of the BSID-II Results of confirmatory factor analyses (CFA) across age levels support the construct validity of the KABC-II At ages 3 4, the WPPSI-III Full Scale IQ correlated 0.76 and 0.81 with the KABC-II MPI and FCI, respectively Academic achievement (Kaufman Test of Educational Achievement, 2nd edition; KTEA-II, Kaufman and Kaufman, 2004b) correlated 0.72 0.74 with the KABC-II MPI and FCI Studies including clinical groups provide further evidence of the KABC-II s validity Construct validity of the WPPSI-III is supported by the factor-analytic studies Criterion validity is supported by correlations of 0.80 0.89, with the following instruments BSID-II, WPPSI-R (Wechsler, 1989), WISC-III (Wechsler, 1991), and DAS (Elliott, 1990a,b) Studies including clinical groups provide further evidence of the test s validity Construct validity of the SB5 was demonstrated in a principal components analysis Criterion-related validity for preschool samples was found in correlation between SB5 and the WPPSI-R (r 0.83) Concurrent validity was demonstrated by correlations of 0.89 with the FS-IQ of the WPPSI-R to 0.77 with the SB-IV Convergent validity was shown with correlations between DAS Verbal Ability and WPPSI-III V-IQ of 0.78 and correlations between DAS Nonverbal Reasoning and WPPSI-II P-IQ of 0.76 DESCRIPTION OF TEST PROCEDURES Most general measures of cognition designed for preschool children tap the global domains of verbal and nonverbal functioning. In addition, a measure of global cognitive ability is yielded from each test, but for most children with developmental disabilities, it is the variability between the separate domains of functioning that is the most important to measure, rather than the global ( average ) cognitive ability score. For example, children with severe language disorders or autistic-spectrum disorders may have a test profile with significantly stronger nonverbal than verbal skills. Children with cerebral palsy or other motoric disorders may struggle in the nonverbal domain, but have intact language skills. Thus, children with developmental disabilities may have great variability between their verbal and nonverbal abilities, which minimizes the meaningfulness of the global cognitive score. To better understand how each of the tests measure verbal and nonverbal abilities, the structures of the five instruments scales are briefly explained in the following sections and the content of their subtests are then described in a series of tables. BSID-II The BSID-II assesses cognitive, motor, and behavioral development of infants and children between the ages of 1 month through 3 1 2 years. The first edition of the BSID (BSID; [Bayley, 1969] was derived from several scales of infant development, including the California First-Year Mental Scale [Bayley, 1933] the California Preschool Mental Scale [Jaffa, 1934] and the California Infant Scale of Motor Development [Bayley, 1936]. The
Table 3. Description of BSID-II Scales BSID-II Scale Mental Motor Behavior rating Description Assesses the child s current level of cognitive, language, and personal-social development and includes items that measure memory, problem solving, early number concepts, generalization, classification, vocalizations, language, and social skills. Measures the child s level of gross and fine motor development via items associated with crawling, sitting, standing, walking, etc., for gross motor movement and items related to the use of writing, grasping, and imitation of hand movements for fine motor movement. This scale is completed by the examiner regarding the child s behaviors during the test administration and assesses the child s attention/arousal (for children under 6 months of age), orientation/engagement toward the tasks and the examiner, emotional regulation, and quality of motor movement. revision of the Bayley Scales includes restandardization to update the norms, extending the age range (formerly ranged from 2 to 30 months), and addressing the shift in interest among clinicians and researchers from assessing normal infants to assessing high risk and developmentally delayed infants. However, a majority of the content of the BSID were retained; items were added to expand the age range and content coverage. Items were changed or deleted if they were considered difficult to administer, identified as biased against racial/ethnic groups, or were redundant with other items. The BSID-II consists of three scales: the Mental Scale, Motor Scale, and Behavior Rating Scale (Table 3 describes the content of each scale). In 2005, the Bayley Scales of Infant and Toddler Development, 3rd edition (Bayley-III) will be published by The Psychological Corporation. The Bayley-III will assess five domains: cognitive, language, motor, social-emotional, and adaptive behavior. An optional Behavior Rating Scale will also be included with the Scales. The Bayley-III will also include suggestions to help parents plan for their child, based on the results of the assessment. KABC-II The KABC-II is a measure of the processing and cognitive abilities of children and adolescents between the ages of 3 years 0 months and 18 years 11 months. It is organized into three levels (Age 3, Ages 4 6, Ages 7 18), the first two are appropriate for preschoolers. The original K-ABC, published in 1983 was rooted in neuropsychological theories Sperry s [1968] cerebral specialization approach and the Luria Das successive-simultaneous processing dichotomy. Both the Sperry and Luria Das models are characterized by a dual-processing approach that has been well supported by a large body of cognitive and neuropsychological research [Neisser, 1967; Das et al., 1979]. In its second edition, the K-ABC underwent major revision structurally and conceptually. The K-ABC s theoretical foundation in Luria s [1966] sequential-simultaneous processing theory and cerebral specialization theory was modified and supplemented in the second edition. Unlike the original K-ABC; the KABC-II is founded in Luria s three Blocks; and has a second theoretical foundation Cattell- Horn-Carroll (CHC; [Carroll, 1997; Flanagan et al., 2000b] giving examiners more flexibility in interpretation (Table 4 explains how these two theories are applied to the test). To create the dual theoretical basis, 10 new subtests were created and 8 old ones were removed, while 8 original K-ABC subtests were retained. The KABC-II offers two batteries for preschool-age children, one for age 3 and another for children aged 4 6. Depending on the age level of the child and the interpretive approach that the clinician chooses to take, the KABC-II yields from one to five scales. At Age 3, there is only one scale, a global measure of ability, composed of either five subtests (Mental Processing Index MPI) or seven subtests (Fluid-Crystallized Index FCI). For Ages 4 6, subtests are organized into either three scales (Luria model) or four scales (CHC model): Sequential/Gsm, Simultaneous/Gv, and Learning/Glr are in both models, and Knowledge/Gc is only in the CHC model. A Nonverbal scale is also available at all ages. The KABC-II scales are described in Table 4, and the subtests that comprise each scale are outlined and briefly described in Table 5. WPPSI-III The WPPSI-III is a measure of cognitive functioning of children from ages 2 years, 6 months to 7 years, 3 months. Its age range is divided into two age bands (2 6 to 3 11 and 4 0 to 7 3), each with its own battery of subtests. The WPPSI-III offers a Full Scale IQ (FS-IQ) that represents the overall level of cognitive ability for children when the range of scores in the profile is not highly variable. The test also yields a Verbal IQ (V-IQ) that is a measure of acquired knowledge, verbal reasoning, and comprehension and a Performance IQ (P-IQ) that is a measure of fluid reasoning, spatial processing, attentiveness to detail, and visual-motor integration [The Psychological Corporation, 2002], pp. 135 136). The WPPSI-III adds a General Language Composite (GLC) that measures receptive and expressive vocabulary abilities (but not higher-level processing of language) and for the older age band a Processing Speed Quotient (PSQ) that measures processing speed (it is also effected by attention concentration, distractibility, visual memory, planning ability, visual-motor coordination, and compulsiveness). Mainly motor responses are required on the Performance scale (pointing, placing, or drawing) and spoken responses are usually required on the Verbal scale. Wechsler s test for preschoolers has a long history. In 1967, the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) was developed to meet the growing need of how to evaluate programs such as Head Start. The WPPSI was basically developed as a downward extension of many of the WISC subtests, but provided simpler items and an appropriately aged standardization sample. Unfortunately, the WPPSI accommodated the narrow 4 to 6 1 2 year age range, failing to meet the needs of program evaluations because most of the new programs were for ages 3 5. However, the WPPSI has continued to be improved and renormed, which lead the WPPSI to have two revisions, one in 1989 and its most recent in 2002. For the 2 6 to 3 11 age band and the 4 0 to 7 3 age band, WPPSI-III 200 MRDD RESEARCH REVIEWS MEASURES OF COGNITION FOR PRESCHOOL LICHTENBERGER
Table 4. Luria and CHC Conceptualizations of KABC-II Scales Administered to Preschoolers Name of KABC-II Scale Luria Conceptualization CHC Conceptualization Learning/Glr Learning Ability Long-Term Storage and Retrieval (Glr) Reflects an integration of the processes associated with all three of Luria s Blocks, placing a premium on the attention-concentration processes that are in the domain of Block 1, but also requiring Block 2 coding processes and Block 3 strategy generation to learn and retain the new information with efficiency. Sequential and simultaneous processing are associated primarily with Luria s Block 2, and pertain to either a step-by-step (sequential) or holistic (simultaneous) processing of information. Storing and efficiently retrieving newly-learned, or previously learned, information. Sequential/Gsm Sequential Processing Short-Term Memory (Gsm) Measures the kind of coding function that Luria labeled successive, and involves arranging input in sequential or serial order to solve a problem, where each idea is linearly and temporally related to the preceding one. Simultaneous/Gv Simultaneous Processing Visual Processing (Gv) Measures the second type, or simultaneous, coding function associated with Block 2. For its tasks, the input has to be integrated and synthesized simultaneously (holistically), usually spatially, to produce the appropriate solution. As mentioned earlier, the KABC-II measure of simultaneous processing deliberately blends Luria s Block 2 and Block 3 to enhance the complexity of the simultaneous syntheses that are required. Taking in and holding information, and then using it within a few seconds. Perceiving, storing, manipulating, and thinking with visual patterns. Knowledge/Gc (This scale is not included in the Luria model) Crystallized Ability (Gc) Demonstrating the breadth and depth of knowledge acquired from one s culture. Knowledge/Gc is included in the CHC system for the computation of the FCI, but it is excluded from the Luria system for the computation of the Mental Processing Index (MPI). Only the MPI and FCI are offered for 3-year-olds. (Table adapted from Kaufman and Lichtenberger [2005]), p. 14). subtests are categorized as core, supplemental, or optional. Core subtests are those that comprise the V-IQ, P-IQ, and FS-IQ. The composition of the scales for each age group is presented in Figures 1 and 2. In the younger age bracket, two core subtests comprise the V-IQ and two subtests comprise the P-IQ. The four subtests of the V-IQ and P-IQ together yield the FS-IQ for children aged 2 6 to 3 11. In the older age bracket, three subtests comprise the V-IQ and three subtests comprise the P-IQ. In addition to the six subtests of the V-IQ and P-IQ, an additional core subtest (Coding) is added in the calculation of the FS-IQ for those aged 4 0 to 7 3. For both age groups the GLC comprises two subtests: Receptive Vocabulary and Picture Naming (a supplemental subtest for children under age 4, and an optional one for those aged 4 and above). Only the older age bracket has a fourth standard score, the PSQ, which is composed of Coding and Symbol Search (a supplemental subtest). Because GLC and PSQ require the administration of noncore subtests, these two global scores are supplements, not core standard scores. A description of WPPSI-III subtests is provided in Table 6. MRDD RESEARCH REVIEWS MEASURES OF COGNITION FOR PRESCHOOL LICHTENBERGER SB5 The SB5 is an individually administered measure of cognitive abilities for children, adolescents, and adults from ages 2 to 85. The SB5 replaces the Fourth Edition of the Stanford-Binet (SB IV) that was published in 1986. Changes were made in the revision of the SB IV with the addition of a fifth factor (Visual-Spatial Processing), and with modification of the memory factor s content to more heavily emphasize working memory rather than short-term memory. The SB5 also increased the breadth of concepts measured by the Nonverbal IQ, which now covers five areas. The SB5 is based on the CHC theory of cognitive functioning, and measures 5 of the 10 broad CHC abilities: Fluid Intelligence (Gf), Crystallized Knowledge (Gc), Quantitative Knowledge (Gq), Visual Processing (Gv), and Short-Term Memory (Gsm). The SB5 comprises 10 subtests that yield a FS-IQ, two domain scores (V-IQ and Nonverbal IQ), and five factor indexes (Fluid Reasoning, Knowledge, Quantitative Reasoning, Visual-Spatial Reasoning, and Working Memory). Administration begins with two routing subtests (Vocabulary and Object Series/ Matrices). These routing subtests determine the developmental starting point for the remaining subtests. The SB5 subtests and scales are outlined and briefly described in Table 7. DAS The DAS is an individually administered battery of cognitive and achievement tests designed to be administered to children and adolescents between the ages of 2 years, 6 months through 17 years, 11 months. The British Ability Scales (BAS; Elliott, 1979) was published in Great Britain and was the forerunner to the DAS. In 1984, Colin Elliott began development of an American version of the BAS. The theoretical basis for the DAS is the CHC g factor of general intelligence. The DAS cognitive battery consists of 17 subtests that divide into three levels: Preschool Level (ages 2 6 to 3 5), Upper Preschool Level (ages 3 6 to 5 11), and the School-Aged Level (ages 6 0 to 17 11). Depending on the child s age, the core battery consists of four to six subtests. The cognitive battery yields a composite score or General Conceptual Ability score, in addition to lower level composite scores, called Cluster scores. For preschool-aged children, two Cluster 201
Table 5. Subtests that Comprise KABC-II Scales for Ages 3 5 Age at which Subtest is Administered Scale and Subtests Core Supplementary Nonverbal Description Sequential/Gsm Subtests Word Order 3 5 - - The child touches a series of silhouettes of common objects in the same order as the examiner said the names of the objects; more difficult items include an interference task (color naming) between the stimulus and response. Number Recall 4 5 3 - The child repeats a series of numbers in the same sequence as the examiner said them, with series ranging in length from 2 to 9 numbers; the numbers are single digits, except that 10 is used instead of 7 to ensure that all numbers are one syllable. Hand Movements - 4 5 3 5 The child copies the examiner s precise sequence of taps on the table with the first, palm, or side of the hand. Simultaneous/Gv Subtests Triangles 3 5 - - For most items, the child assembles several identical rubber triangles (blue on one side, yellow on the other) to match a picture of an abstract design; for easier items, the child assembles a different set of colorful rubber shapes to match a model constructed by the examiner. Conceptual Thinking 3 5-3 5 The child views a set of 4 or 5 pictures and the child identifies the one picture that does not belong with the others; some items present meaningful stimuli and others use abstract stimuli. Face Recognition 3 4 5 3 5 The child attends closely to photographs of one or two faces that are exposed briefly, and then selects the correct face or faces, shown in a different pose, from a group photograph Gestalt Closure - 3 5 - The child mentally fills in the gaps in a partially completed inkblot drawing and names (or describes) the object or action depicted in the drawing. Block Counting - 5 - The child counts the exact number of blocks in various pictures of stacks of blocks; the stacks are configured such that one or more blocks is hidden or partially hidden from view. Pattern Reasoning 5 6-5 The child is shown a series of stimuli that form a logical, linear pattern, but one stimulus is missing; the child completes the pattern by selecting the correct stimulus from an array of 4 to 6 options at the bottom of the page (most stimuli are abstract, geometric shapes, but some easy items use meaningful). Learning/Glr Subtests Atlantis 3 5 - - The examiner teaches the child the nonsense names for fanciful pictures of fish, plants, and shells; the child demonstrates learning by pointing to each picture (out of an array of pictures) when it is named. Atlantis-Delayed - 5 - The child demonstrates delayed recall of paired associations learned about 15 25 min earlier during Atlantis by pointing to the picture of the fish, plant, or shell that is named by the examiner. Rebus 4 5 - - The examiner teaches the child the word or concept associated with each particular rebus (drawing) and the child then reads aloud phrases and sentences composed of these rebuses. Rebus-Delayed - 5 5 The child demonstrates delayed recall of paired associations learned about 15 25 min earlier during Rebus by reading phrases and sentences composed of those same rebuses Knowledge/Gc Subtests Riddles 3 5 - - The examiner provides several characteristics of a concrete or abstract verbal concept and the child has to point to it (early items) or name it (later items). Expressive Vocabulary 3 5 - - The child provides the name of a pictured object. Verbal Knowledge - 3 6 - The child selects from an array of 6 pictures the one that corresponds to a vocabulary word or answers a general information question Note: Knowledge/Gc subtests are only administered if giving the CHC model. (Adapted from Table 1.2 of KABC-II Manual [Kaufman and Kaufman, 2004a]). scores, Verbal Ability, and Nonverbal Ability are yielded from 4 to 6 subtests. The composite scores are composed of core subtests, only those subtests with relatively high g loadings. There are also 2 5 diagnostic subtests for each level, which measure specific abilities that are less related to g, such as speed of information processing and short-term memory; however, the diagnostic subtests do not contribute to the composites. The core and diagnostic cognitive subtests are 202 MRDD RESEARCH REVIEWS MEASURES OF COGNITION FOR PRESCHOOL LICHTENBERGER
Fig. 1. WPPSI-III scale structure for ages 2 6 to 3 11. Picture Naming can be substituted for a core Verbal subtest if necessary (From E. O. Lichtenberger and A. S. Kaufman 2004, p 9. Copyright 2004 by Wiley. Reprinted with permission). Fig. 2. WPPSI-III scale structure for ages 4 0 to 7 3. Either supplemental Verbal subtest may be substituted for one core Verbal subtest. Supplemental Performance subtests may be substituted for one core Performance subtest (From E. O. Lichtenberger and A. S. Kaufman 2004, p 10. Copyright 2004 by Wiley. Reprinted with permission). listed for the Lower and Upper Preschool Levels in Table 8. MEANING OF TEST RESULTS Scores from measures of general cognitive ability are important to interpret within the context of a child s medical and social history as well as other test results. Before interpreting the results, it is also important to consider how valid a given assessment is. If a caregiver observed the testing of the child, inquire about whether the child responded to the assessment in a manner that was typical for that child (i.e., some young children do not respond well to strangers and may MRDD RESEARCH REVIEWS MEASURES OF COGNITION FOR PRESCHOOL LICHTENBERGER not perform to the best of their abilities in the assessment). On the basis of behavioral observations and opinion of the caregiver who observed the assessment, you can determine the validity of the results. For example, if the child s behaviors indicated that he or she may not have understood the directions of the tasks, or the child could not remain focused and attentive enough to complete the tasks at hand, then the test results need to be interpreted cautiously or may not be valid. In addition, if the caregiver indicates that the child was not responding in a manner that reflects his or her typical ability, then the results should also be interpreted cautiously. Bear in mind that any given testing is a sample of a child s behavior in a controlled situation. Thus, even if the scores resulting from an assessment are deemed as invalid or if scores need to be viewed with caution, invaluable qualitative information is yielded about how the child approached a task, responded to the social situation, responded to directions and redirection, as well as other observable qualities such as attention, tolerance for frustration, and so forth. Comparing Cognitive Domains Interpretive information can be gleaned by examining the discrepancy be- 203
Table 6. Description of WPPSI-III Subtests Performance Subtests Block Design Child reproduces patterns made from 1- or 2-colored blocks. Matrix Reasoning The child looks at an incomplete matrix and selects the missing section from 4 or 5 response options. Picture Concepts Child is presented with 2 or 3 rows of pictures and chooses one picture from each row to form a group with a common organizational concept. Object Assembly Child is required to fit puzzle pieces together to form a meaningful whole. Picture Completion Child identifies what is missing from pictures of common objects. Symbol Search Child indicates, by marking a box, whether a target symbol appears in a series of symbols Coding Using a key, the child draws symbols that are paired with simple geometric shapes. Verbal Subtests Information Child must either point to a picture or verbally answer brief oral questions about commonplace objects and events. Vocabulary Child names pictured items and provides verbal definitions of words. Word Reasoning The child reads an increasingly specific series of one to three clues and identifies the common object or concept being described. Comprehension Child verbally responds to questions about consequences of events. Similarities Child completes a sentence that contains a verbal analogy. Picture Naming The child names pictures that are displayed singularly in the stimulus booklet. Receptive Vocabulary The child looks at a group of four pictures and points to the one that the examiner describes aloud. To view which subtests comprise each WPPSI-III scale, examine Figures 1 and 2. Table 7. SB5 Subtests and the Activities that Comprise them Verbal Subtests Fluid Reasoning Early Reasoning: Examinee describes what is happening in the picture. Verbal Absurdities: Examinee explains orally what is silly or impossible about the statement ready by the examiner. Verbal Analogies: Examinee solves word problems orally Knowledge Vocabulary: Early items require a pointing response. Items increase in difficulty requiring single word responses. Upper level items require that words be defined clearly Quantitative Reasoning Quantitative Reasoning, Verbal: Examinee responds verbally to quantitative reasoning problems presented orally and visually. Visual-Spatial Processing Position and Direction: Examinee places a block on the part of the picture specified orally by the examiner or the examinee responds verbally to oral questions. Working Memory Memory For Sentences: Examinee recalls orally presented sentences. Last Word: Examinee listens to a question, answers the question, and then recalls the last word in the question. Nonverbal Subtests Fluid Reasoning Object Series/Matrices: Examinee selects the best alternative to complete a series or a matrix. Knowledge Procedural Knowledge: Examinee shows what you typically do with a pictured object. Picture Absurdities: Examinee points to and tells what is silly or impossible in each picture Quantitative Reasoning Quantitative Reasoning, Nonverbal: Examinee solves a problem by pointing to a response Visual-Spatial Processing Form Board: Examinee uses blue plastic pieces to assemble a pattern shown on the stimulus page. Form Patterns: Examinee must place the shapes back into the correct spots in the form board after seeing the examiner remove them. Working Memory Delayed Response: Examinee must remember which cup hides an object. Block Span: Examinee taps blocks in the same sequence demonstrated by the examiner. Subtest names are listed in bold and underneath each of the subtests, the activities that comprise each are listed and described in italics. tween scores from the separate domains of the cognitive tests, to determine if differences are significant and relatively uncommon. For example, consider the following comparisons for the cognitive tests: On the BSID-II examine the MDI versus PDI On the KABC-II, the separate indexes can be contrasted (measuring sequential processing/short-term memory, simultaneous processing/ visual processing, learning/longterm memory, and knowledge) On the WPPSI-III, the V-IQ versus P-IQ can be examined (as well as the GLC and PSQ) On the SB5, the V-IQ versus Nonverbal IQ can be examined and the five factor indexes can be contrasted On the DAS, the Verbal versus Nonverbal Ability clusters can be compared. A variety of factors can lead to unusual differences across domains: language deficits, learning deficits, visual-motor deficits, neuromuscular 204 MRDD RESEARCH REVIEWS MEASURES OF COGNITION FOR PRESCHOOL LICHTENBERGER
Table 8. DAS Core and Diagnostic Cognitive Subtests for the Preschool Level Core Cognitive Subtests Preschool-Age Level 2 6 to 3 5 3 6 to 5 11 Description Block Building Child reproduces two- or three-dimensional block designs using four or eight wooden blocks. Verbal Comprehension Child points to picture or manipulates objects in response to oral instructions from the examiner. Picture Similarities Child places a card with a picture under one of four displayed pictures that the card shares an element or concept with. Naming Vocabulary Child gives the name of an object or picture. Pattern Construction Child constructs geometric designs with flat squares or solid cubes. Copying Child draws abstract geometric designs. Early Number Concepts Child demonstrates knowledge of numerical concepts such as size, number, order, addition, and subtraction. Diagnostic Cognitive Subtests Recall of Digits Child recalls digits that were presented orally. Recognition of Pictures Child recognizes, in a group of four to seven similar pictures, the one, two, three, or four picture that had been briefly presented previously. Block Building As described earlier. Matching Letter-Like Forms Child finds an identical match to an abstract figure from six choices. Recall of Objects Child recalls as many pictures as possible from memory after viewing pictures on a card for 20 60 s. All core subtests from the GCA at their respective year levels. (Adapted from [Elliott, 1990a]). problems, or noncognitive factors such as fatigue and inattention. Examining the specific pattern of errors made on the scales can help identify if a particular area of functioning is problematic. Because tests of infant and early childhood global cognitive development have been shown to be relatively poor predictors of later IQ or academic functioning [Bayley, 1933; Siegel, 1981; Black and Matula, 2000], clinicians should interpret results of preschool assessment, as primarily relevant for developing immediate early intervention programs (and making longterm prognosis about the child s developmental skills should be avoided). An examination of the differences between scores on a cognitive test is merely a beginning to interpretation. The meaningfulness of the test results is greatly enhanced when it is grounded in an empirically supported theoretical model of the structure of intelligence [Flanagan et al., 2000a]. The Horn- Cattell-Carroll (CHC) theory has been identified as one of the most well researched and empirically supported theories; which represents a viable framework from which cognitive functioning is interpreted. Detailed descriptions of this theory and its application to cognitive testing are available from Flanagan and her colleagues [McGrew and Flanagan, 1998; Flanagan and Ortiz, 2001]. Although in-depth explanation of interpretation of the five instruments discussed in this article is not possible in this limited space, the interested reader can find more detail in the tests manuals as well as in texts by the following authors: For the BSID-II see Black and Matula [2000]; For the KABC-II see Kaufman et al. [2005]; For the WPPSI-III see Lichtenberger and Kaufman [2004]; For the SB5 see Roid and Barram [2004]; For the DAS see Sattler [2001]. MRDD RESEARCH REVIEWS MEASURES OF COGNITION FOR PRESCHOOL LICHTENBERGER Special Considerations for Test Interpretation of Children with Developmental Disabilities Much information can be gleaned from traditional cognitive measures, even if the test administration procedures have been adapted to meet the needs of a disabled child. For example, modifications during administration may include removing time requirements, using multiple-choice formats, pantomiming responses, pointing responses, stabilizing a child s hand, or enlarging objects. When such modifications are made, clinicians must use their judgment to determine whether the standardized norms are applicable and valid. In some instances, it may be possible to obtain a valid domain score, but not a battery composite score. For example, a child with motor impairment may have a valid score on the WPPSI-III V-IQ, SB5 V-IQ, the DAS Verbal Ability, or the KABC-II Sequential/Gsm, Learning/Glr, and Knowledge/Gc, but may not have interpretable scores from the nonverbal scales of these 205
same tests. In contrast, children with severe linguistic deficits or disorders such as Autism, may not be able to obtain a meaningful estimate of their cognitive ability with their verbal domain score, but may demonstrate their cognitive strengths on nonverbal scales. For example, such children s strengths might be visible on the Bayley PDI, WPPSI-III P-IQ, SB5 Nonverbal IQ, the DAS Nonverbal Ability, or the KABC-II Nonverbal Index. In addition, within the verbal realm, children with linguistic difficulties or autism may also show variability, with severely impaired expressive language skills and more intact receptive language skills. When interpreting the results of a cognitive assessment of a developmentally delayed child, also consider that instruments scales are not pure measures of the verbal and nonverbal domains. That is, the nonverbal scales also have some verbal demands (e.g., understanding the verbally presented directions) and some verbal scales have nonverbal components (e.g., visual stimuli or a pointing response). Thus, if a child does not perform as you would have predicted based on their suspected areas of strength and deficit, then it is necessary to consider the nuances of the subtests stimuli and response demands to decipher what may have caused an unexpected result. STRENGTHS, BENEFITS, CAUTIONS, AND LIMITATIONS Each of the five instruments reviewed in this article have benefits and limitations that are worth mentioning. This is not a comprehensive list of all minor strengths or weaknesses for each battery, but rather is a list that points out noteworthy strengths of the batteries, and highlights limitations that may warrant caution by clinicians in using and interpreting the various instruments. Benefits and limitations are listed in the following global categories: test floors, administration and subtest demands, psychometric qualities, scoring, and interpretation. Test Floors Limitations The test floor of one of the five instruments reviewed is especially problematic for assessing children with developmental disabilities. The BSID-II Mental and Motor Development Indices do not go below 50. Therefore, only mild mental retardation can be accurately assessed. Although norms that go below 50 have been extrapolated and published by others, Robinson and Mervis [1996], the BSID-II itself does not include such data. However, in the forthcoming third edition of the BSID, the floor and ceiling of the subtests will be extended to improve assessment of lower functioning children. Benefits In contrast to the BSID-II, both the KABC-II and WPPSI-III made significant improvements in the test floors in their most recent editions. On the KABC-II, there are better floors for younger children and better ceilings for gifted children. The WPPSI-III has a lower age range and has separate subtest groupings for the two age groups, and has added items to measure very low and very high-functioning individuals. The WPPSI-III has also broadened the measurement of nonverbal abilities, which is beneficial for developmentally delayed children. Administration and Subtest Demands Limitations The one of the most notable limitations of the BSID-II is that many of the items require either expressive language or a good understanding of spoken language for success. However, many high risk and developmentally delayed young children have speech and/or language delays or impairments, making it difficult to assess their cognitive abilities using the BSID-II. A weakness in the subtest demands for the KABC-II is its emphasis on speed of processing for a few subtests so that differentiation occurs with older bright examinees (that is, bonus points are included for some of the more advanced items, which mainly effect school-age children or adolescents). However, the manual does allow examiners to calculate scores with the effect of speed removed, which helps to compensate for this weakness. The DAS materials are organized in a complex manner, which can make learning the test a challenge for examiners. The administration and scoring criteria in the manual are also more complicated than that of many other tests of cognitive ability. Benefits The BSID-II offers flexible administration of items, yet still allows examiners to follow standardized procedures. Thus, while there is a specified set of items to administer, the order in which one administers the items can be modified, which helps to maintain the child s attention and rapport during the testing. The forthcoming Bayley-III will have fewer manipulative and more play-based items to facilitate administration. Scoring will be available via computer as well as manually. The manual will also provide Bayely-III data on children with highincidence clinical diagnoses, providing evidence of the test s validity. The third edition of the WPPSI eliminated bonus points for speed, got rid of Geometric Design, and simplified test directions for many tasks by deemphasizing difficult basic concepts. The KABC-II also introduced several novel tasks with stimuli that are appealing to young children, making the test more play-like keeping a young child easily engaged. The SB5 has similarly been made more appealing to young children by increasing the number or toys and colored manipulatives. The number of subtests was reduced from 15 to 10 on the SB5, a more manageable number when assessing young children. Similar to the other tests, the DAS materials are appealing to most young children and the administration and scoring criteria in the manual are thorough (albeit complex). Psychometric Qualities Limitations One of the WPPSI-III s limitations is that the battery is heavily weighted with word knowledge tasks (i.e., 3 of the 14 subtests: Receptive Vocabulary, Picture Naming, and Vocabulary), yet has zero measures of short-term memory. Short-term memory is an especially important skill to assess for young children, and is included in most theories of intelligence, such as Guilford s or CHC. Another limitation of the WPPSI-III is that a subtest with poor factorial validity (Picture Concepts) was included as one of only three subtests that contribute to P-IQ. A limitation of the KABC-II is that for 3-year-olds it offers only an overall cognitive score (either MPI, FCI, or NVI), but no domain scores. However, beginning at age 4, separate scores for different domains may be obtained. Benefits The five tests reviewed here all have large-well stratified normative bases, and strong reliability, validity, and factor analytic properties (except for the WPPSI-III Picture concepts subtest mentioned earlier). A unique strength of the KABC-II is that it consistently produces lower 206 MRDD RESEARCH REVIEWS MEASURES OF COGNITION FOR PRESCHOOL LICHTENBERGER