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Go to CuriosityStream.com/Psych to learn more [ ♪INTRO ]. Parents were once warned against raising children to speak more than one language.

It's bad for kid's cognitive development, they were told, and will result in bad grades and a lower IQ! And that ridiculous claim is still sometimes repeated, especially here in the United States. But times have mostly changed.

Now, if you believe the headlines, being bilingual makes you smarter and more creative. And those headlines don't come from nowhere. There is research which suggests that bilingualism provides some specific cognitive advantages.

And you can hardly blame the press for covering these studies, because it's such an appealing idea: teach your child French and you get a better child! more creativity, multitasking, and academic performance in other subjects all for free! But if that sounds too good to be true, that's because it is. You see, there are also studies that don't find an advantage.

Those don't get the same excited coverage. In this case, though, the media aren't really the ones to blame. When it comes to the effects of bilingualism on the brain, there's confusion and bias on the scientific side, too.

And it all goes to show just how hard it can be to understand what really goes on in our heads. Learning another language definitely has benefits that's no one can argue against — like, for example, you'll know another language! And it even makes sense that it could benefit your brain in other ways.

The main benefit is thought to be to executive functions — the processes that control complex cognitive tasks like attention, problem solving, planning, and so on. And that hypothesis isn't unreasonable. It's thought that these processes are kind of like muscles — the more you use them, the better you get at them.

And research has found that all sorts of cognitively challenging activities improve executive functions. Like, playing video games can make you better at assessing risks and placing bets. And music training can improve your ability to focus on specific tasks.

Since juggling two or more languages in your brain is cognitively challenging in a lot of ways, it could have similar positive effects. Constantly switching between vocabularies could help you be a better multitasker, for example, if it made you generally better at quickly shifting your brain from one thing to another. But more than one analysis of the research has found that the evidence for such benefits is weak and inconsistent.

For example, a 2015 review in the journal Cortex concluded that over 80% of the tests conducted over four years of studies don't show a bilingual advantage. Those that did had serious problems with their methodology — like, they had small sample sizes or inadequate controls. But there's a more foundational problem with the published research on bilingualism: it doesn't tell the whole story.

This was pointed out by a study published in 2014 in the journal Psychological Science. The researchers started by looking at the research presented at conferences from 1999 to 2013. Roughly half these presentations found some advantage for bilingualism and half didn't.

Then they looked at which ended up getting published in journals, and found something striking: 68% of the positive studies got published, while only 29% of the negative ones did. The published and unpublished studies didn't consistently differ based on sample size, experimental tests used, or statistical power. A study simply had a better chance of getting published if it supported the idea that bilingualism gives people a cognitive boost, and a worse chance of getting published if it showed the opposite, regardless of the quality of the work.

This is a phenomenon known as publication bias, and it's not unique to this situation, it's not unique to psychology. It's a pervasive issue scientists from all fields are grappling with because it can undermine the research that is published. For example, a 2018 meta-analysis of over 150 studies on adults did find bilinguals were slightly better at some executive functions.

But those advantages disappeared when the researchers corrected for publication bias. Now, it's important to point out that none of this amounts to proof that there are no cognitive advantages to bilingualism. But it's clearly going to take a lot more work to figure out if there are, and if so, whether any of them are unique — or if studying Japanese is basically the same as playing.

Minecraft, from your brain's perspective. This also applies to another often-repeated claim about bilingualism: that it can delay the onset of dementia. Again, the idea seems reasonable at first glance, as other complex cognitive activities do seem to prevent or delay dementia.

But, a 2015 review of the literature found that the effects of bilingualism on dementia are very inconsistent. And that's not all. There were some suspicious patterns in the research methods.

You see, prospective studies — the ones that enroll people before they show symptoms and then test them as they age — tended not to show an effect of bilingualism. Positive results were mostly found in retrospective studies, which look at people after they've been diagnosed. Subjects in that kind of study may not be representative of the whole population, and it's harder to pick good controls.

That all suggests that the researchers might have been seeing what they wanted in the data, and having their judgement biased by their expectations. So not only do studies on bilingualism have issues with publication bias, there may be straight-up bias in many of them. And this all means we really don't know if learning a second language can give you some kind of subtle cognitive advantage or keep your brain healthy as you age.

Still, we can say that learning a language does make you smarter. No matter what, you'll know something you didn't know before. So in that sense, of course it makes you smarter.

And it's not going to hurt you, like they thought in the old days. Not only that, with your new fluency, you can experience whole new bodies of literature and arts, travel to interesting places, and talk to more people. So yeah, being able to speak multiple languages has lots of benefits, even if it's not boosting your brain indirectly.

If the idea of traveling the world and experiencing new things sounds awesome to you, I have a feeling you'll like the videos offered by Curiosity Stream. CuriosityStream is a subscription streaming service that offers over 2,400 documentaries and non­fiction titles from some of the world's best filmmakers, including exclusive originals. For example, if languages are your jam, you might like their original documentary The History of English.

It takes you on a trip through time and around the world to understand how this particular language came to be a “linguistic superpower”. And they have videos on nature, history, technology, and society and lifestyle, too. For as little as $2.99 a month, you can get access to all of them.

And if that's not enough for you, as a SciShow Psych viewer, you can get your first 31 days completely free! All you have to do is sign up at curiositystream.com/Psych and use the promo code ‘psych', that's P-S-Y-C-H during the sign-up process. [ ♪OUTRO ].