Maybe it's time to blow the dust off that Putonghua CD and learn something new.
Many recent studies have pointed out that bilingualism seems to be good exercise for the brain and later in life might even help delay the onset of dementia.
But what if it's a self-selecting crowd? What if the people who learned two languages are just smarter to begin with?
To help rule that factor out, researchers at the University of Edinburgh in Scotland studied 853 people who first took an intelligence test in 1947 when they were about 11 years old as part of a group called the Lothian Birth Cohort 1936, and retested them again around 2008 to 2010, when they were in their early 70s.
"Reflecting the society of its time," the authors wrote in the Annals of Neurology, "the cohort is remarkably homogenous; they are English native speakers, of European origin, born, raised, and living in and around Edinburgh. None was an immigrant."
That was good for the study, given that it mostly wipes out potentially confounding differences, such as ethnicity and immigration status, that might complicate the relationship between bilingualism and cognitive decline.
A total of 262 of the septuagenarians (roughly a third of the study group) reported having learned at least one language other than English enough to communicate in it. Of those, 195 said they learned it before age 18; 65 said they learned it thereafter. (It's unclear what happened to the remaining two people. Also, few participants seemed to have learned their second language in early childhood: 19 of the under-18 crowd said they learned it before age 11.)
The researchers gave the participants a battery of cognitive tests, including tests of their verbal reasoning, their vocabulary and reading abilities, their verbal fluency and their ability to process information quickly.
Bilingual speakers performed much better than expected from their baseline cognitive ability, particularly in reading and in general intelligence. And those who knew three or more languages performed even better.
Bilingualism's effects were comparable to factors such as "the effect of variation in the gene for apolipoprotein E, physical fitness, and [not] smoking", the authors wrote.
Learning a language seemed to make as much difference in later-in-life cognitive decline as a gene that's been tied to risk of Alzheimer's disease and smoking (or non-smoking) habits.
These participants mostly learned their second languages after age 11. So the researchers couldn't study the perfect, early, parallel acquisition of both languages, what they call the "classical" scenario.
But in this way, the results actually make a very compelling point - you don't have to be a fluent speaker of a language to get the benefits, and you can start later in life, too.
"Millions of people acquire their second language later in life: in school, university, or work, or through migration or marriage to a member of another linguistic community. Many never reach native-like perfection," the study authors pointed out.
"For this population," they continued, "our results are particularly relevant; bilingualism in its broad definition, even if acquired in adulthood, might have beneficial effects on cognition."