Questions and Answers
Question #12


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Questions and Answers

 

Question # 12

Is level of performance as important as pattern of performance for the classification of NLD?


Levels of performance are important considerations for clarifying the adaptive status of persons with NLD. As with virtually every neuropsychological condition, however, patterns of performance in NLD are much more predictive of behaviour than are levels of performance. The gaps between rote and pragmatic verbal skills, vocabulary and visual-spatial-organizational skills, simple motor and complex psychomotor skills, and the like are the principal dimensions that contribute to concurrent and predictive validity in NLD. Indeed, in the instances just mentioned, levels of performance in any one of these areas contribute relatively little to the prediction of academic, social, vocational, and psychosocial functioning of persons with NLD.

There are several psychometric implications of this principle, one of which is the following that has to do with concurrent validity. Scaled scores of 10 on any of the Wechsler subtests are "average." However, if a youngster obtains subtest scaled scores of 10 on Block Design and Object Assembly (i.e., "normal" scores) within a context of subtest scaled scores of 14 on Information and Vocabulary, the likelihood of an eventual classification of NLD is considerably higher than would be the case were the latter (Verbal) scaled scores 10 instead of 14. In short, this is an example where pattern of performance is a much more important consideration than is level (even when that level is "normal") with respect to the classification of NLD. Indeed, it is an example of where "more" (in this case, a Verbal subtest scaled score of 14 instead of 10) is indicative of a much greater probability of NLD than is "less."


Addendum
Many clinicians are familiar with persons who exhibit the syndrome of NLD and are thought to be “very bright”—that is, have measured IQs within the above-average, even superior, range.  The syndrome of NLD is also more or less evident in persons who are thought to exhibit “intellectual disability” (e.g., Fetal Alcohol syndrome, Kabuki syndrome, see NLD and Neurological Disease for these and other examples).  These are syndromes wherein “level” (of IQ) is far less important than is “pattern of performance” (as in visual-spatial-organizational vs. rote verbal skills) in the determination of the presence or absence of the syndrome of NLD in the behavioural phenotype of the disorder.

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