Individuals who speak two languages regularly appear to build a cognitive reserve that significantly helps delay the onset of mild cognitive impairment that comes later in life, a study published in the journal Neuropsychologia suggests.
The study provides a first-of-its-kind comparison of the brain-health benefits associated with multilingualism across a spectrum of language proficiency and use. To make the comparison, researchers in Spain constructed a scale of bilingualism ranging from people who speak one language but have a passive knowledge of a second language to individuals with an excellent command of two languages, which they use interchangeably in daily life.
In the United States, more than a fifth of the population older than age 5 speak a language other than English at home, according to the most recent five-year estimates from the “American Community Survey” (no age breakdown was available). For more than 13 percent of Americans, that language is Spanish. About 1 percent speak Chinese at home, including the Mandarin and Cantonese dialects, and just under 1 percent total speak a variety of Native American languages.
Of the more than 60 million Americans who speak a language other than English at home, about 3 in 5 speak English very well, data from the U.S. Census Bureau survey shows.
In Spain the researchers recruited 266 people age 60 and older living in Barcelona, where Spanish and Catalan are commonly spoken. The participants included 63 healthy individuals, 135 previously diagnosed with mild cognitive impairment and 68 with Alzheimer’s disease. Each participant’s language proficiency was then correlated with the age at which neurological symptoms were first observed.
“We saw that people with a higher degree of bilingualism were given a diagnosis of mild cognitive impairment later than people who were passively bilingual,” study corresponding author Marco Calabria, a professor of health sciences studies at the Open University of Catalonia and Pompeu Fabra University in Barcelona, said in a statement.
Psycholinguist Mark Antoniou of Western Sydney University in Australia had that same line of reasoning in his article in the January 2019 Annual Review of Linguistics.
“Because a bilingual person has mastery of two languages, and the languages are activated automatically and subconsciously, the person is constantly managing the interference of the languages so that she or he doesn’t say the wrong word in the wrong language at the wrong time,” he told The Washington Post. “The brain areas responsible for that are also used when you’re trying to complete a task while there are distractions.
“The task could have nothing to do with language; it could be trying to listen to something in a noisy environment or doing some visual task,” Antoniou said. “The muscle memory developed from using two languages also can apply to different skills.”
Calabria likens active bilingualism to a form of linguistic gymnastics that strengthens cognitive functions, such as executive control. Executive control, often called executive function, is what we think of as being human, being able to organize tasks inside your head and regulating your behavior. People need that ability to smoothly handle moving from one language to another.
“This system, in the context of neurodegenerative diseases, might offset the symptoms.” Calabria said. “So when something does not work properly as a result of the disease, the brain has efficient alternative systems to solve it, thanks to being bilingual.”