To delineate score differences between the Wechsler Adult Intelligence Scale-IV (WAIS-IV) and the WAIS-IV México in the assessment of balanced bilingual Mexican Americans and to determine the efficacy of five hold measures in predicting summary scores in each version.

Hold measures were WAIS-IV Information, Vocabulary, and Matrix Reasoning subtests, picture vocabulary, and the Test of Premorbid Function (English)/Word Accentuation Test (Spanish). Using a repeated measures design, 60 neurologically intact participants were tested in a counterbalanced order, with WAIS-IV version as the repeated measure (mean intertest interval = 5.68 days). To minimize practice effects, the five visual-perceptual subtests, which contain the same items in each version, were administered only once during the initial session.

All mean WAIS-IV México index/subtest scores were significantly higher than the U.S. equivalents (Full-Scale IQ by about .5 SD). Unexpectedly, most (83%) participants educated in the US to at least a high school level had numerically equal or higher scores on the U.S. version. Means on WAIS-IV language format indices/subtests were lower than those of visual-perceptual format indices/subtests within both versions (excepting Processing Speed Index/subtests in the U.S. version). All hold measures significantly predicted WAIS-IV summary scores for the U.S. version. Similarly for the México version, except for the Word Accentuation Test.

When evaluating a balanced bilingual Mexican American, opting for the WAIS-IV México version will yield higher scores across the Full-Scale IQ, indices, and all core subtests unless the patient was educated in the US to at least a high school level.