The Wechsler Adult Intelligence Scale discrepancy index: a neuropsychological evaluation.

Abstract

Traditionally, the discrepancy between the Wechsler Adult Intelligence Scale (WAIS) Verbal IQ and Performance IQ has been used in clinical practice as an indicator of both brain damage and lesion lateralization. The present study investigated the relationship between this discrepancy index and brain damage, lesion lateralization, type of brain damage (acute vs. chronic), Full Scale IQ, and gender. The WAIS was administered to five groups of subjects (N = 335): left, right, diffuse, and nonspecific brain-damaged groups, and psychiatric controls. No relationship was found between this index and any of the preceding categories with the exception of Full Scale IQ. Caution is suggested in the use of the discrepancy index as a diagnostic indicator of brain damage and/or lesion lateralization. Traditionally, the discrepancy between Verbal IQs and Performance IQs of the Wechsler Adult Intelligence Scale (WAIS) has been used in clinical practice as an indicator of both brain damage and lesion lateralization. Several studies have suggested that large Verbal IQ/ Performance IQ discrepancies may be indicative of brain damage and, more specifically, that depressed Verbal scores are associated with left-hemisphere damage, whereas depressed Performance scores are associated with right-hemisphere damage (Parsons, Vega, & Burns, 1969; Satz, 1966; Satz, Richard, & Daniels, 1967; Simpson & Vega, 1971; Vega & Parsons, 1969; Zimmerman, Whitmyre, & Inelds, 1970). The validity of this relationship, however, has been questioned by some investigators. For example, Smith (1966) collected data from several medical centers and found that 66.3% of his left-hemisphere-damage group had a higher Verbal IQ than Performance IQ, a finding that clearly contradicts the above interpretation. Smith concluded that his findings were compatible with Wcchsler's claim (1958) that any type of organic damage causes impairment in Performance IQ. Other investigations, however, have suggested that Smith's