| This study tries to explain why "some studies have failed to show this bilingual advantage, suggesting that it might depend on the type and degree of bilingualism", by laying out evidence for the "type and degree of bilingualism. Here are the facts that the article established: - Lifelong degree of bilingualism predicts delay in age of onset for all clinical measure of Mild Cognitive Impairment (MCI). - This is NOT true for Alzheimer's Disease patients. - This prediction was independent of occupation, education, and job attainment. The second bullet point isn't properly emphasized in the article, but it's directly from the abstract. The researcher has a hypothesis that multilingualism improves Cognitive Reserve [1], and, and Cognitive Reserve has already been established to have an effect on the timeline of Alzheimer's disease related pathology. [2] That being said, it's also true that "AD is the most common etiology of MCI and mild dementia" [3], and the researcher has a hypothesis that the multilingualism improves Cognitive Reserve. Based on the existing hypothesis of how CR and AD interact, the lack of correlation in AD patients could make sense, and should not be seen as counter-evidence to the bilingualism increases CR hypothesis. [1] https://en.wikipedia.org/wiki/Cognitive_reserve [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3507991/#S2titl... [3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4185370/#S5titl... |