THE 3RD AND 4TH FACTORS OF THE WISC-III - WHAT THEY DONT MEASURE

Factor analysis of the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) continues to demonstrate support for the Verbal, Pe rformance, and Full Scale IQs, as well as for the Verbal Comprehension (VC) and Perceptual Organization (PO) factors. With the addition of t he Symbol Search subtest, however, the factor analysis reported in the examiner's manual yielded two additional factors rather than just one . There is, however, no early evidence that the third and fourth facto rs are clinically interpretable. This study examined the relationship between the WISC-III third and four factors and other neuropsychologic al and behavioral measures. Results indicated that although Freedom Fr om Distractibility (FFD) and Processing Speed (PS) correlated signific antly with VC and PO factors, the FFD and PS factors did not correlate significantly with any of the other measures of attention. The most r obust correlations were between measures of immediate/working memory a nd FFD and PS. When comparing clinical groups (LD/no ADHD, ADHD Predom inantly Inattentive, and ADHD Combined Type), no differences emerged o n the FFD or PS factors. The clinical validity of these factors remain s questionable. The significant relationship between WISC-III factors and measures of immediate/working memory is promising, but in need of additional research.