Empirical Implications of Matching Children With Specific Language Impairment to Children With Typical Development on Nonverbal IQ.

This study determined the effect of matching children with specific language impairment (SLI) and their peers with typical development (TD) for nonverbal IQ on the IQ test scores of the resultant groups. Studies published between January 2000 and May 2012 reporting standard nonverbal IQ scores for SLI and age-matched TD controls were categorized into those that matched and did not match children with SLI and TD on nonverbal IQ. We then compared the nonverbal IQ scores across matching criterions within each diagnostic category. In studies that matched children on nonverbal IQ, children with SLI scored significantly higher on nonverbal IQ tests relative to children with SLI in studies that did not match on this criterion. Therefore, it appears that the nonverbal IQ performance of children with SLI is not comparable across studies that do and do not match samples on nonverbal IQ. This suggests that the practice of nonverbal IQ matching may have unintended consequences for the generalization of research findings to the broader SLI population.