The frequent switching between languages in bilinguals' brains has led many to ask whether this lifelong exercise also makes bilinguals better at controlling other mental processes, giving them a cognitive edge. That remains to be determined. But in a new study, researchers took a more nuanced look at cognition in bilinguals, and rather than focusing on the question of the so-called bilingual advantage, examined how bilinguals used their brains while performing a simple cognitive task. And, as it turns out, they used them differently than monolinguals.
The idea of the bilingual advantage is supported by a number of studies that have shown that bilinguals may have enhanced executive control — a set of mental skills that help us manage our cognitive processes, from working memory, to multitasking and problem-solving. But some scientists have expressed skepticism about the strength of evidence that suggests bilinguals have a cognitive advantage over monolinguals. In a 2014 study, researchers examined conference abstracts outlining ongoing studies on bilingualism and executive control. They then followed up to see which of those studies eventually got accepted for publication in scientific journals and found that the studies whose results failed to support the idea of the bilingual advantage were less likely to get published than those that supported it. This led them to think that there might be a publication bias that skews the literature on bilingualism's cognitive boost.
In the new study, researchers once again looked at executive control in bilinguals versus monolinguals, this time examining the brain mechanisms behind it. The study involved 20 Catalan-Spanish bilingual undergraduate students, who had used both languages regularly since they were infants, and 19 Spanish monolingual undergraduate students.
The participants were given a simple, classic task that involves using executive control: they were asked to press a button whenever they saw a grey circle on the screen and not to press a button whenever they saw a yellow circle. Meanwhile, the researchers observed their brain activity using fMRI.
It turned out there were no differences in how fast and accurately the people in the two groups performed the task.
But the researchers did notice a difference in the way that bilinguals and monolinguals used two brain networks: the left fronto-parietal network (FPN) and the salience network. The left FPN involves the brain areas related to language control and verbal working memory, whereas the salience network, which comprises the inferior frontal gyrus, the insula, and the dorsal anterior cingulate, is linked to processing relevant unexpected stimuli. The results suggested that bilinguals might develop the involvement of the executive control networks differently than monolinguals.
"There are a lot of people out there who want to say 'Well, the only thing that matters to show that bilingualism is good for the executive function system is if we can show that bilinguals actually do the task faster,'" Ellen Bialystok of York University in Toronto, who wasn't involved in this study, told Braindecoder. But what really matters here is how they perform the task, she said.
"And what this study shows is that bilinguals are using a different mechanism," she said.
Moreover, even the mechanism itself is less important than "the simple point that they are doing something different," Bialystok added.
The results suggest that the brains of bilinguals may be wired differently. This idea is not far fetched—the brain changes when it's used differently. And the new findings are important because this different wiring could be linked to better brain health outcomes that some studies have found in aging bilinguals.
"This study in conjunction with others that have shown the whole configuration, the wiring of a bilingual brain, is different, helps us to start thinking about more consequential outcomes like resistance to symptoms of dementia," Bialystok said.
In a study published in 2010 in Neurology, Bialystok and her colleagues looked at 102 lifelong bilinguals with Alzheimer's disease and 109 monolinguals who also had the disease. They found that the bilinguals in the study had been diagnosed about four years later and had reported the onset of symptoms about five years later than the monolinguals. Research conducted in other parts of the world yielded similar results.
Researchers don't really know why symptoms of Alzheimer's disease may be delayed in bilinguals. "But if we can show, as this study does, that the entire configuration of these really important networks is different in young bilinguals, this gives us some sense of where to look," Bialystok said.
One hypothesis that Bialystok and her team are currently exploring is that the symptoms of the disease in bilinguals are delayed through compensation, Bialystok said. Normally, memory tasks are performed by the middle part of the brain, which is also the first to be affected by Alzheimer's. That is why memory failure is one of the first symptoms of the disease, Bialystok explains. But, as the middle part of the brain begins to break down in a bilingual person with the condition, the front part of the brain, where executive control systems are located, may be recruited "for simple memory tasks that it would not normally get involved with," Bialystok said.
"And it can do that precisely because the wiring is different," she said.