Verbal IQ–performance IQ differentials in traumatic brain injury samples

Several studies of head trauma utilizing the Wechsler Adult Intelligence Scale (WAIS) reported large sample differentials between verbal IQ (VIQ) and performance IQ (PIQ), leading some writers to claim that the VIQ is largely unaffected by traumatic brain injury (TBI), and that a superiority of VIQ over PIQ should be expected. In contrast, our review of Wechsler Adult Intelligence Scale-Revised (WAIS-R) studies indicates that although TBI sample PIQ means are often depressed relative to VIQ means, the differences are small and sometimes in the opposite direction. Possible reasons for the discrepancy between our WAIS-R review and those of an earlier review of WAIS studies are discussed. Clinically, the lack of a VIQ–PIQ difference should never be used to infer that a TBI has not occurred.