WISC-IV unusual digit span performance in a sample of adolescents with learning disabilities

Accurate identification of symptom magnification is essential when determining whether or not obtained test data are valid or interpretable. Apart from using freestanding symptom validity tests, many researchers encourage use of embedded measures of test-related motivation, including ones derived from the Digit Span subtest of the Wechsler scales. Such embedded measures are based on identification of performance patterns that are implausible if the test taker is investing full effort; however, it is unclear whether or not persons with preexisting cognitive difficulties such as specific learning disabilities (LD) might be falsely accused of poor test motivation due to actual but impaired working-memory skills. This study examined the specificity of such measures by reviewing performance of 86 adolescents with LDs on three measures embedded in the Wechsler Intelligence Scale for Children-Fourth Edition-namely, Digit Span (DS), Vocabulary-DS differences, and Reliable Digit Span (RDS) scores. Results indicate that while RDS is likely insensitive to impairments associated with LD, other DS measures may have an unacceptably high false-positive rate, especially if Canadian normative data are used to calculate scores.