The ability to speak two languages is often credited with bringing serious benefits to a speaker's brain. Real world advantages aside, the bilingual brain is thought to make for a stronger executive control system (what "The Bilingual Advantage" author, psychologist Ellen Bialystok, calls the organ's "general manager").
Since bilingual speakers are essentially multitasking as they switch between languages (or among them, in the case of polyglots), the reasoning goes that they're better at multitasking in general.
But as Maria Konnikova reported in The New Yorker, this perceived advantage might not exist, and researchers often find evidence that bilingualism doesn't bring with it an extra dose of focus or poise.
Dutch psychologist Angela de Bruin, who is the story's principal source, matriculated in a graduate linguistics and neuroscience program "expecting to study the extent to which her bilingual brain was adapted to succeed," Konnikova writes.
But when she put participants through four "inhibitory control" tasks — the type in which you're made to ignore one stimulus in order to count or otherwise keep track of others — de Bruin found that three of these yielded no evidence of advantages for bilinguals over their single-language peers. This experiment went against the scientific consensus that speaking two languages is better than speaking one, calling into question the seeming ubiquity of positive results about bilingualism.
"We thought, Maybe the existing literature is not a full, reliable picture of this field," de Bruin told Konnikova. She decided to try to get to the bottom of things in a clever way: She compared the number of "counter-advantage" ideas and studies floating around scientific conferences to the number that went on to survive in the more rigorous world of peer-reviewed publication.
The rationale was straightforward: conferences are places where people present in-progress research. They report on studies that they are running, initial results, initial thoughts. If there were a systematic bias in the field against reporting negative results—that is, results that show no effects of bilingualism—then there should be many more findings of that sort presented at conferences than actually become published.
And that's exactly what de Bruin found. Across 69 conferences held between 1999 and 2012, the presented results were split about evenly between the "pro" and "meh" camps of the bilingual advantage debate. But 68% of the former studies were published in a scientific journal, compared to 29% of those promoting what might just be an unpopular finding: that there are "no differences between monolinguals and bilinguals or... a bilingual disadvantage," de Bruin wrote.
It could just be that those studies are less rigorous, and that sub-par experiments and analyses — not bias — explain why they never made it into a journal. But even if they are, their backers could be credited for actively seeking to avoid letting the scientific community fall into an echo chamber, where "sacred" ideas grow, even when they may be faulty.
De Bruin does allow that there's a strong correlation between being able to speak two languages and keeping dementia at bay — for a few years, at least.
In two studies Bialystok was involved in, lifelong bilingualism was found to delay the onset of dementia and Alzheimer's disease by 4 and 4.3 years, respectively, compared to their monolingual peers.
A more recent and extensive study in Hyderabad, India — where bilingualism is prevalent — confirms this correlation.
More than half of the 648 subjects spoke two or more languages, and "developed dementia 4.5 years later than the monolingual ones." The benefit was found "across Alzheimer disease dementia as well as frontotemporal dementia and vascular dementia." (Frontotemporal dementia leads to cell degeneration in the brain, though its cause is unknown. Vascular dementia, on the other hand, is the result of poor or interrupted blow flow to the brain, such as that caused by strokes.)
Incidentally, patients enjoyed this resilience even if they were functionally illiterate, or unable to read or write the multiple languages they spoke.
But more significant to de Bruin's own research is that the study in Hyderabad linked the dementia-fighting benefits to the executive function boost that de Bruin is doubting. As the study notes:
The constant need in a bilingual person to selectively activate one language and suppress the other is thought to lead to a better development of executive functions and attentional tasks with cognitive advantages being best documented in attentional control, inhibition, and conflict resolution.
What seems certain, then, is that bilingualism does help ward off dementia, whether by empowering the brain's executive system or for still unknown reasons.
And while arguments and (quieter) counter-arguments fly regarding the possible advantages of bilingualism, it might be the pragmatic stance that wins out: speaking more than one language means being able to order lunch far from home. While researchers continue to investigate, there are obvious advantages to being a polyglot, even without the much-celebrated, intellectual boost it might provide.
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