Bilingual proficiency and cognitive reserve in Persian-English bilingual older adults

More than genetic and physical influences, different environmental stimuli affect brain reserve, and bilingualism is one example. In this study, effect of bilingual proficiency on older adult's cognitive reserve was investigated.

Persian and English versions of the Word Association Test were used among 26 educated older adults with a mean age of 67.52 years who became bilingual in Persian-English early in life. Lexical memory and Bergen dichotic listening tests were performed.

The bilingual proficiency score in all participants was within the range for early bilingualism. The Persian version of Word Association Test content validity index was 98.17 %. The inter-rater reliability for the Persian version of Word Association Test was 0.980, and that for the English version was 0.986. In addition, the intra-rater reliability for the Persian version was 0.857, and that for the English version was 0.954 (p < 0.001). There was significant correlation between the frequency of words expressed in the English Word Association Test and years for which English has been spoken as a second language (p ≤ 0.045). A significant correlation was observed between the bilingual proficiency score and lexical memory score (p < 0.043). Bilingual proficiency score also showed a significant correlation with the dichotic listening scores in all three non-forced, forced-right, and forced-left attention situations (p ≤ 0.045).

These results demonstrated the influence of bilingualism on shaping cognitive reserve in Persian-English bilingual older adults, representing linguistic experience-dependent neuroplasticity.