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Does Bilingualism Protect Against Alzheimer’s Disease?


 

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COPENHAGEN—Being bilingual is unlikely to protect against Alzheimer’s disease, according to research presented at the 2014 Alzheimer’s Association International Conference.

In a study that compared the performance of older people who spoke Welsh and English with people who spoke only English, the bilingual participants did not perform better on executive control tasks, and being bilingual did not contribute to enhanced cognitive reserve.

Linda Clare, PhD

“Indeed, older Welsh–English bilinguals may be disadvantaged, relative to monolinguals, on some indices of executive function,” stated Linda Clare, PhD, Professor of Clinical Psychology and Neuropsychology, Bangor University, in Gwynedd, United Kingdom.

A Prior Link Between Bilingualism and Cognitive Performance
Prior studies have shown that bilingualism may contribute to cognitive reserve, and others have shown that bilingual persons outperform monolingual individuals on nonlinguistic tasks involving response conflict or inhibition.

“The current view is that this bilingual advantage arises because the general executive function system is involved in language processing to deal with the conflict presented by joint activation of the two languages,” noted Professor Clare. “There is, however, a need to examine performance on a wider range of tasks for which executive control is salient.”

The researchers recruited participants from a socially and culturally homogenous community in North Wales. Fifty people ages 60 and older who were bilingual in Welsh and English were compared with 49 monolingual English-speaking participants of equivalent age in 38 executive function tasks. The tasks focused on the domains of mental generativity and speed, working memory, set shifting and switching, and inhibition and management of response conflict. The Lifetime of Experiences Questionnaire was used as an indication of participants’ level of cognitive reserve.

A Monolingual Advantage?
Few significant differences were observed between the two groups of participants. Univariate analyses suggested a monolingual advantage in mental generativity and speed, working memory, and set shifting and switching. The monolingual advantage was less evident in the domain of inhibition and management of response conflict, according to the researchers. Multivariate analysis confirmed the monolingual advantage in working memory and in set shifting and switching. Furthermore, variations in the degree of daily use of the two languages in the bilingual group did not significantly affect performance.

“The findings suggest that there are differences in the cognitive profiles of monolinguals and bilinguals across a range of executive tasks,” commented Professor Clare. “In contrast to recent research that has reported either a bilingual advantage or no differences, the present results indicate a tendency for monolinguals to perform better across most task domains.”

These findings, however, are consistent with results from a recent study that compared the performance of people who were bilingual in Welsh and English and participants who spoke English alone at seven stages across the lifespan on dimensional card sorting, Simon, and meta-linguistic tasks, led by Virginia C. Mueller Gathercole, PhD, Professor of Linguistics at Florida International University in Miami.

“A possible explanation for the unexpected observation of a monolingual advantage may lie in the nature of the sociolinguistic context in Wales, where there may be little incentive to inhibit English-language intrusions in conversation, since listeners will readily understand and accept any such intrusions, and where any such code switches are common in the everyday conversations of Welsh speakers,” Professor Clare theorized.

Colby Stong

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