Cognitive and Intellectual Measures
A central component of all psychological assessment has been a measurement of intellectual or cognitive ability. As this pertains to children, the purpose is typically to predict and plan for academic capacity and appropriate educational programming.
Tests of this nature have also allowed clinicians and educators to detect students who may be at risk for learning problems and benefit from special services.Of the major general cognitive tests, each is based on different theoretical models, but all share a fundamental similarity: separate assessment of verbal and nonverbal skills, with scores combined to yield a general composite. In the rehabilitation population, children whose illness or disability differentially affects verbal or visual-spatial skills require a more sophisticated selection and analysis of tests. These children are more likely than the typical population to show significant differences on different types of skill sets, and composite scores may not provide much useful information. For example, a child who scores in the average range on visual-spatial tasks and in the impaired range on verbal tasks may be given an overall composite score in the low-average range—which does little to describe the child's actual abilities and even less in terms of guiding programming.
In cases of significant physical or sensory impairment, such as hemiparesis, clinicians are simply not able to fully and adequately assess the full range of intellectual functioning. Tests that require rapid bilateral fine motor skills have to be modified, thus negating valid interpretation, and replaced with less involved tests that require pointing. These tests cannot be assumed to measure precisely the same skills— and may even be skipped altogether in favor of using scores on verbal-response tests as the primary index and then assuming that the score reflects general capacity across domains.
This practice is ill-advised even in normal populations, much less in children where there is evidence of neurologic impact that may differentially affect various skill sets. In general, with children like these, scores on cognitive tests should be carefully interpreted, with cognizance of limitations, and used as part of a larger body of neuropsychological assessment that uses more sophisticated and specified measures to best assess the full span of skills that are commonly affected by illness or disability.The Wechsler scales include the Wechsler Intelligence Scale for Children, 4th Edition (WISC-IV) (75), the Wechsler Adult Intelligence Scale, 3rd Edition (WAIS-III) (76), and the Wechsler Preschool and Primary Scale of Intelligence, 3rd Edition (WPPSI-III)
(77). The factor structure of the WISC-IV was significantly changed from the previous edition. The WISC-IV includes a full-scale score made up of four separate composites, each of which is made up of several different subtests. The four composites are verbal comprehension, perceptual reasoning, working memory, and processing speed. The core working memory subtests are primarily verbal in nature, and the core processing speed subtests are primarily nonverbal in nature. The WISC-IV is designed for use with children ages 6-16 years. The WAIS-III is used with individuals ages 16-89 years. It yields a full-scale score comprised of verbal and performance (nonverbal) scaled scores. The verbal scale includes two separate indexes: verbal comprehension and working memory. The performance scale includes the perceptual organization and processing speed indexes. Each index is made up of several different subtests. The WPPSI-III has two different score structures, depending on age level. For children age 2½ to 4 years, there is a full-scale score comprised of verbal, performance, and general language composites. For children ages 4 to 7 years, 3 months, there is one additional composite score: processing speed.
Important considerations in the assessment of preschool-age children are addressed in the following section, “Instruments for Use With Young Children.”The Stanford-Binet Intelligence Scales, 5th Edition
(78) is designed for use with individuals age 2-89 and up. The full-scale score is made up of five factor indexes: fluid reasoning, knowledge, quantitative reasoning, visual-spatial processing, and working memory. Each factor index includes separate assessments of nonverbal and verbal skills. It should be noted that some of the “nonverbal” tasks require significant receptive language skills, which may complicate interpretation in a child with a basic discrepancy in verbal and nonverbal skills.
The Kaufman Assessment Battery for Children, 2nd Edition (K-ABC-II) (79) was designed for use with children ages 3-18. It is unusual in that guidelines are provided for interpreting results within two different theoretical models: the Luria neuropsychological model and the Cattell-Horn-Carroll psychometric model. Using the Luria model can provide some coherence within a broad neuropsychological assessment. Under this model, there are five scales (sequential processing, simultaneous processing, planning ability, knowledge, and learning ability), each comprised of multiple subtests. There is also a distinct nonverbal index that can be administered entirely through nonverbal gestures and responses, which can be useful for children with certain disabilities.