Use of the Intermediate Category Test in Arithmetic Disability Subtypes

The Intermediate Category Test (ICT) is a test of nonverbal reasoning and executive functioning, but its single general score may be difficult to interpret in the context of a particular clinical case. In this study, the ICT was applied to groups of subjects with very specific cognitive impairments, so that what is known about those groups, along with patterns of performance on the ICT, might help describe what the ICT measures in greater detail. The convergent and divergent validity of the ICT was examined using archival data from 81 children with arithmetic learning disabilities. Children were divided into groups based on the presence (n=55) or absence (n=26) of a comorbid verbal learning disability. All children were given the ICT, Wechsler Intelligence Scale for Children-Revised, Wide Range Achievement Test-R, Wide Range Assessment of Memory and Learning, Wisconsin Card Sorting Test, Kaufman Assessment Battery for Children Matrix Analogies subtest, and Trail Making Test. A variance test revealed that subtests I and II do not contribute significantly to variance in the ICT. Factor analysis demonstrated different factor structures for children with and without comorbid verbal disabilities. A factor composed of subtests IV, V and VI, and a second factor composed of subtests III and IV was present in children with isolated arithmetic learning disability, with only subtests III and VI strongly related to nonverbal abstract reasoning. In contrast, two ICT factors in children with a combined-type learning disability were composed of subtests V and VI, and III and IV, respectively. None of these factors had strong relationships with measures of nonverbal reasoning, although subtests V and VI were significantly related to arithmetic achievement.