Bilingual Studies Reveal Flaw In How Info Reaches Mainstream

Transcript

STEVE INSKEEP, HOST:

You know, there's a theory that if you know more than one language, it makes your brain stronger. That theory has shown up in scientific journals and newspapers and magazines. Es impresionante pero es la verdad. The truth is it's a bit more complicated. And that fact might expose a flaw in how scientific research reaches the mainstream. Our own David Greene spoke about that with NPR's Shankar Vedantam.

DAVID GREENE, HOST:

Hey, Shankar.

SHANKAR VEDANTAM, BYLINE: Hi, David.

GREENE: Well, let's start with this theory. What is it?

VEDANTAM: Well, the theory is that speaking multiple languages - being bilingual - actually has benefits to your brain. And there's lots of people who are really excited about this idea. And it's based on the fact that there have been dozens of studies that show that when you learn multiple languages, you have better executive control.

GREENE: Executive control. What exactly is that?

VEDANTAM: Well, executive control is like the traffic cop function in your brain.

GREENE: OK.

VEDANTAM: It helps you do lots of other things.

GREENE: So this is, like, the part of your brain that helps you sort of multitask. And people who might have better control are able to multitask. And other people might get totally distracted.

VEDANTAM: Precisely. Here's the problem with that construction, David. In 2009, researchers at the University of Edinburgh in Britain - they published a study showing that bilingual speakers could resist distraction better than monolingual speakers. So that totally fits with the theory. But I recently spoke with Angela de Bruin. She's recently revisited the subject based on her personal knowledge of what actually happened. It turns out the researchers in that 2009 paper actually conducted four experiments. Three out of the four did not show that bilinguals were less distractible than monolingual speakers. I let de Bruin explain what happened next.

ANGELA DE BRUIN: One of those tasks showed an effect of bilingualism. And that's the task that was published. Now, the three other tasks did not show any effect of bilingualism at all. And those tasks never made it into a publication. They were just put in a file drawer. So we had four studies, but only one was published. And that's the successful one, showing an effect bilingualism.

GREENE: Isn't that kind of misleading - to just publish the study that sort of backed up this theory?

VEDANTAM: It is misleading, David. And full credit to de Bruin for coming clean about what happened. In fact, one of the authors of the 2009 paper tried to replicate the experiment that found a positive benefit for bilingualism. And that replication failed to work. So in other words, there were four experiments. Three did not show benefits, and they weren't published. One showed a benefit and was published. But it couldn't be reproduced. And then the reproduction was not published.

GREENE: So why not publish any of these negative studies?

VEDANTAM: Well, there are multiple reasons David. But the first is that when a study doesn't produce a result, it's hard to know if that's because there wasn't an effect or just because the study was somehow not conducted properly. And the second problem is that scientific journals really want to publish studies that find something. They want to publish studies that have a positive result.

GREENE: They want news.

VEDANTAM: Exactly. And so negative studies - as they're called -tend not to get published.

GREENE: Is this a widespread problem in science?

VEDANTAM: De Bruin actually thinks this is a problem that goes beyond just the one set of papers that are co-authors worked on in 2009. She went back and analyzed studies of bilingualism that were presented at scientific conferences. Scientists often present the first look at their work at these conferences. And you're more likely to find eclectic work presented at scientific conferences. She analyzed how often these presentations at scientific conferences ended up in prestigious journals. And what she found was that the quality of the studies was not important. What mattered was whether the study found bilingualism had brain benefits. Here she is again.

DE BRUIN: What we found was that 63 percent of abstracts supporting a bilingual advantage were published compared to only 36 percent of the challenging studies.

GREENE: You know, Shankar, just listening to that, it makes me less likely to trust a scientific study.

VEDANTAM: I think that's exactly right, David. There's been a lot of concern in science about this kind of publication bias affecting the integrity of science and the perceptions of integrity of science. There's been a lot of efforts to try and clean it up in recent years. On the specific question of bilingualism, this study doesn't debunk the idea that learning multiple languages can be good for you. It can allow you to read a different kinds of literature and travel more widely. So there's all kinds of benefits to learning multiple languages. What it does suggest, though, is that the brain benefits of bilingualism - that idea might be a little more complicated than has been presented so far.

GREENE: That's Shankar Vedantam. He regularly joins us here on Morning Edition to talk about social science research. You can follow him on Twitter @hiddenbrain. And while you're at it, you can follow this program at @NPRInskeep, @NPRGreene, and @MorningEdition. Transcript provided by NPR, Copyright NPR.