Native Spanish-speaker's test performance and the effects of Spanish-English bilingualism: results from the neuropsychological norms for the U.S.-Mexico Border Region in Spanish (NP-NUMBRS) project.

We aimed to investigate whether or not demographically-corrected test scores derived from the Neuropsychological Norms for the U.S.-Mexico Border Region in Spanish (NP-NUMBRS) would be less accurate if applied to Spanish-speakers with various degrees of English fluency. One hundred and seventy primarily Spanish-speaking adults from the NP-NUMBRS project completed a comprehensive neuropsychological test battery. T-scores adjusted for age, education, and sex (but not degree of bilingualism), were derived for each test utilizing population-specific normative data. English fluency was assessed via the Controlled Oral Word Association Test in English (F-A-S), and Spanish fluency with "P-M-R," and degree of relative English fluency was calculated as the ratio of English language words over total words produced in both languages. Effects of degree of bilingualism on the NUMBRS battery test scores (raw scores and T-scores) were examined via Pearson's product moment correlation coefficients, and language groups (Spanish dominant vs. relative bilingual) were compared on demographically adjusted T-scores via independent samples t-tests. Higher Spanish-English bilingualism was associated with higher education and SES, and was significantly associated with higher raw scores on all tests, but only associated with higher T-scores on a limited number of tests (i.e., WAIS-III Digit Symbol, Symbol Search, Letter-Number Sequencing and Trails B). Degree of Spanish-English bilingualism generally did not account for significant variance in the normed tests beyond the standard demographic adjustments on most tests. Overall, the normative adjustments provided by the NP-NUMBRS project appear applicable to native Spanish speakers from the U.S.-Mexico border region with various degrees of Spanish-English bilingualism.