Learn a second language to slow ageing brain's decline
- 18:03 03 June 2014 by Catherine de Lange
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Feel too old or too stupid to learn a second language? It may be worth persevering. A study that tracked hundreds of Scottish people for decades is the strongest evidence yet that speaking an extra language slows the mental decline that accompanies ageing. The benefits hold regardless of your IQ and even if you learn your second tongue as an adult.
Previous studies have shown that people with Alzheimer's disease who are fluent in two languages exhibit symptoms of the condition four or five years later than people who are monolingual, and that people who are bilingual perform better in some cognitive tests. However, it has been difficult to disentangle the effects of knowing multiple language from other factors. For example, some studies have compared bilingual immigrants and their families with monolingual natives.
To resolve the issue, Thomas Bak of the University of Edinburgh, UK, and his colleagues turned to the Lothian Birth Cohort study, which has tracked about 1100 people born in 1936 in and around Edinburgh. All were monolingual English speakers at age 11, when they had taken a battery of cognitive tests.
The study wasn't designed to investigate language effects. But 853 of the participants were tracked down when they were in their early 70s. It transpired that almost one-third, or 262, of them had learned to speak at least one additional language and that 65 had learned it after the age of 18.
As a result, the study provides a unique research opportunity, says Ellen Bialystok at York University in Toronto, Canada, who was first to discover that being bilingual delays the onset of Alzheimer's. "You have this absolutely homogenous sample of Scottish kids – all monolingual – and you let them go off and have their lives and see what happens," she says.
Bak's team gave the participants cognitive tests and compared these with the test scores from when they were 11. Those who had learned an extra language performed better in the cognitive tests in their 70s than would be predicted from their earlier scores, indicating that the extra language itself is beneficial.
The strongest effects were on general intelligence and reading. This further suggests that the benefits are down to the extra language, because if they were simply due to greater intelligence, you would expect there to be a boost across all skills. "For the first time we address the chicken and egg question," says Bak. His team found that the benefits to the ageing brain were comparable to physical activity, or not smoking.
Bialystok says the cognitive benefits seen in the Scottish study chime with her own work on bilingual people with Alzheimer's disease, suggesting that the same beneficial processes are at work.
How could languages protect the brain? A leading theory is that people who speak several languages constantly activate all the available words in each one before choosing the appropriate expression, giving them a mental workout.
Journal reference: Annals of Neurology, doi.org/s3c
This article will appear in print under the headline "Learn a second language to slow mental decline"