Wechsler Adult Intelligence Scale‐III Inter‐Subtest Scatter: A comparison of brain‐damaged patients and normal controls

This study assessed the validity of Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) inter-subtest scatter (as measured by the scaled score range) as an indication of cognitive impairment due to brain dysfunction. Participants were 174 individuals with documented brain damage. Means for age, education, and WAIS-III full-scale IQ were 49.19 years (SD = 15.33), 12.57 years, (SD = 2.78), and 88.45 (SD = 17.78). The scatter ranges for brain-damaged participants were compared with those of the WAIS-III standardization sample. Results indicated that the full-scale IQ is significantly correlated with amount of scatter, r(172) = .42, p < .0001, so that a definitive answer to the question requires control of full-scale IQ. In the present analyses, inter-subtest scatter among the individuals for the sample as a whole was no greater than that for persons in the standardization sample, but subtest scatter was significantly greater for participants with IQs ≥ 90. This finding suggests that there may be small differences in scatter between brain-damaged persons and normal controls, but that scatter is relatively insensitive to the presence of brain damage or dysfunction. Therefore, interpretation of marked inter-subtest variability as a sign of brain damage appears unwarranted. © 2006 Wiley Periodicals, Inc. J Clin Psychol 62: 1319–1326, 2006.