Wechsler VIQ versus PIQ differences in cerebral dysfunction: a literature review with emphasis on sex differences.

For the past three decades neuropsychologists have published results which indicated that left-sided cerebral dysfunction affected the Wechsler Verbal Scale whereas right-sided dysfunction affected the Performance Scale. Recent investigations have indicated that the effects of cerebral dysfunction on performance of the Wechsler Scales may be different for males and females. In view of these reports, the present review considered 24 studies (28 samples) which have reported Wechsler IQ scores in patients with unilateral or bilateral cerebral dysfunction. Eight studies (10 samples) used the Wechsler-Bellevue I, whereas 16 studies (18 samples) employed the WAIS. In these 28 published samples, there were four exceptions to the hypothesis of lower mean VIQ in patients with left-hemisphere lesions, and lower mean PIQ in patients with right-hemisphere dysfunction. Of the four exceptions to this "rule", two samples contained only women, while a third contained only patients with missile wounds of the frontal lobe. One sample appeared to be a true exception, and could not be accounted for by lesion location or sexual composition of the sample. The studies reviewed appear to add additional support to the hypothesis of sex differences in the effects of unilateral lesions. Therefore, insofar as published mean values for the Wechsler Scales are concerned, the specific effects on Verbal versus Performance IQ appear more prominently in males.