There's always been a lot of talk about the benefits of bilingualism on the brain - so what's the deal? Let's review a bit of the news reporting on the subject. And see below for a list of articles on the subject.
Older research claims bilinguals under-performed
In years long gone, research was published that had some negative suggestions about bilinguals.
From an NPR article in 2016: "Bilingual students under-performed monolingual English speakers and had lower IQ scores." However, it seems this research "looked at socially disadvantaged groups," according to Antonella Sorace at the University of Edinburgh, in Scotland. "This has been completely contradicted by recent research" that compares more similar groups to each other.
"In the last 20 years or so, there's been a virtual explosion of research on bilingualism," says Judith Kroll, a professor at the University of California, Riverside.
It seems that: "The research that finally put that prejudice to bed was conducted by Jim Cummins and Virginia Collier at the University of Toronto. They discovered that students who had a native language literacy would display CALP (“cognitive academic language proficiency”) in a secondary language far sooner than those who didn’t have a strong native language." This is according to an article in The Guardian, from 2018.
Most exciting benefit: improved executive function
From The Independent in 2016: Bilingual children showed more activity in areas of the brain related to 'executive function', which governs tasks such as problem-solving or shifting attention.
First of all, what the heck is executive function, amiright?
According to a New York Times article from 2012: "The collective evidence from a number of such studies suggests that the bilingual experience improves the brain’s so-called executive function — a command system that directs the attention processes that we use for planning, solving problems and performing various other mentally demanding tasks. These processes include ignoring distractions to stay focused, switching attention willfully from one thing to another and holding information in mind — like remembering a sequence of directions while driving."
Additionally, it seems that having multiple languages in the brain causes a bit of a traffic jam and requires a decision making process to select the right language and words to address the matter at hand. And , it turns out, that's the benefit.
"It forces the brain to resolve internal conflict, giving the mind a workout that strengthens its cognitive muscles." NYT. 2012
Most emotionally rewarding: Improved social skills
According to a New York Times article from March 2016, “Bilingual students also have better social skills than students who speak just one language because they are better at communication. Psychologists gave communication tasks to children ages 4 to 6 years old, and the bilingual students were better at considering others’ perspectives.
"Interestingly, we also found that children who were effectively monolingual yet regularly exposed to another language — for example, those who had grandparents who spoke another language — were just as talented as the bilingual children at this task. It seems that being raised in an environment in which multiple languages are spoken, rather than being bilingual per se, is the driving factor."
Most encouraging: Lifelong impact
Seems some researchers have found the effects of bilingualism no matter the age of the student:
NPR: Do these same advantages accrue to a child who begins learning a second language in kindergarten instead of as a baby? We don't yet know. Patterns of language learning and language use are complex. But Gigi Luk at Harvard cites at least one brain-imaging study on adolescents that shows similar changes in brain structure when compared with those who are bilingual from birth, even when they didn't begin practicing a second language in earnest before late childhood.
Most promising: long-term benefits
This subject has gotten the most media attention lately: bilingualism's possible impact on long term brain function (read: preventing Alzheimer's and other dementia-related diseases). While no research is conclusive as of yet, all the signs are all positive.
NYT: "Bilingualism’s effects also extend into the twilight years. In a recent study of 44 elderly Spanish-English bilinguals, scientists led by the neuropsychologist Tamar Gollan of the University of California, San Diego, found that individuals with a higher degree of bilingualism — measured through a comparative evaluation of proficiency in each language — were more resistant than others to the onset of dementia and other symptoms of Alzheimer’s disease: the higher the degree of bilingualism, the later the age of onset."
One possible downside
One article noted an interesting issue - the ability (or lack thereof) to have 100% acquisition of one language. The author writes:
"It’s as if some bilinguals can speak, say, 95% of two languages, rather than a 100% of one. For those who want their children to be articulate and sophisticated language users, that missing 5% is a major hole, especially if you want them fully to appreciate, say, Dante or Shakespeare. But as François Grosjean, the French psycholinguistic said, a bilingual is not “two monolinguals in one” and shouldn’t necessarily be judged according to monolingual parameters." The Guardian, 2018
However, this is just screaming for someone to prove him wrong. :)