| The purpose of this study was to determine the clinical significance of the Wechsler Intelligence Scale for Children-Third Edition (WISC-III; Wechsler, 1991) Processing Speed Index (PSI), in a clinically referred sample diagnosed with various learning, attention, social-emotional and/or behavioral disorders. Little is known about the clinical significance of the Processing Speed Index despite the existence of the Index since 1991. In a large, referred sample (N = 980), children with neurogenetic disorders (ADHD, autism, bipolar disorder, and LD) had lower PSI and FDI (Freedom from Distractibility) scores than VCI (Verbal Comprehension) and POI (Perceptual Organization), and Coding was lower than Symbol Search. The majority of children had learning, attention, writing and processing speed weaknesses. This pattern was not found in the other clinical groups. Only PSI was low for children with depression, whereas children with anxiety disorders, oppositional defiant disorder, and mental retardation had no PSI weakness. PSI and POI were both low in children with traumatic brain injury and spina bifida. Study findings have implications for understanding the difficulties children with low PS and comorbid clinical disorders have in a school setting including individualized treatment interventions. The inclusion, and potential impact of, the PSI in the calculation of the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV; Wechsler, 2003) FSIQ is also discussed for children with neurogenetic disorders. |
