Short Wave - Learning A Second Language As An Adult

Episode Date: May 13, 2025

Becoming fluent in a second language is difficult. But for adults, is it impossible? Science says no. In this encore episode, Short Wave host Emily Kwong dissects the "critical period hypothesis," a theory which linguists have been debating for decades — with the help of Sarah Frances Phillips, a Ph.D. student in the linguistics department at New York University. Together, Emily and former Short Wave host Maddie Sofia explore where the theory comes from, how it applies to second-language acquisition and what it means for Emily's efforts to learn Mandarin Chinese as an adult.Have a linguistics or neuroscience question? Email us at [e-mail] — we'd love to hear from you!Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. So Maddie, you and I have known each other for a while now, and I think we're ready to take it to the next level. Oh, my God, are we going white water rafting? No. Are we doing it? No, not today. But I have brought you something just as invigorating and just as vulnerable,

a Kwong family home movie. Yes, I think there's more eggs. Do you leave more eggs? My baby quang. So I'm two years old, and we're on an Easter egg hunt. I got my floral Easter dress. I got my grandparents, Hui and Edgar Kwong, and they are all about this right now. Please, get chocolate for you.

Oh. Oh. Honestly, you still react that way to chocolate. Let's be real. It's true. Emily, you want an egg? That's my uncle, Timothy Kwong. And you'll notice, Maddie, throughout these home movies, and I've brought a few today.

that there are two languages being spoken by our family. Right? There's English, but there's also Mandarin Chinese. Those are my grandparents during Christmas. But for years, all I could say in Mandarin was hello, thank you, and goodbye. English was the only language I knew. Until now. Van?

Chi-Tien. All year, I've been taking Mandarin classes virtually. Oh, no, I got this. Trying to learn this language. And in the back of my brain, I'm wondering, of course, you know, am I too old to try? Please hold. Can you really learn another language as an adult? I have to say restaurant first, don't I?

Right? I don't know. What do you think? So today in the show, we ask some big questions about second language acquisition and get answers from neurolinguist Sarah Phillips. This is Shorewave from NPR. All right, Emily Kwong, today we are talking about the science of learning a second language because you are learning Mandarin Chinese, which like as far as a hobby goes, more power to you, Emily, more power to you. Right? For real, though, it is a hard language to learn.

Language itself, actually, is an incredible ability. If you think about it, that we humans have, it involves many parts of the brain, and the study of language spans across many different disciplines. So bilingualism gets studied in at least three different fields, linguistics, psychology, and cognitive neuroscience. Sarah Phillips is a PhD student in the linguistics department at New York University, and exactly the person I wanted to call up to talk about language learning. Oh, yeah. I remember Sarah from our episode on P-600, like how the brain responds to sentences with confusing grammar or syntax. Yeah, brains and language are her jam. So her parents met in Korea while her father was serving in the Marine Corps, and they raised her bilingual here in the U.S.

Learning Korean was very important to be able to communicate with my mom's side of the family in the same way that growing up speaking African-American English was very important in being able to communicate. communicate and be a part of my dad's other family. She's got a really interesting backstory, and I told her about my project, about taking Mandarin class for two hours every Monday, flashcards on the other nights, watching movies I can't understand, and listen to this. Someone who is engaging in learning a second language, thereby uses another language on a pretty regular basis. That means you're developing bilingual.

So in essence, you are a bilingual. Oh. But, you know, we would probably qualify that. Exactly. A baby bilingual. Maybe as an alternative to baby bilingual, maybe we should think of this as a developing bilingual. Oh, that's pretty cool, though. You're a developing baby bilingual.

And Sarah says, more specifically, because she's a scientist, that I am a developing sequential bilingual, meaning I'm learning a second language after acquiring a first language. But that's really different from a simultaneous bilingual like Sarah, who developed the ability to speak two or more languages in the earliest years of life. And one of the reasons I never tried to learn my heritage language, honestly, is because of something called the critical period hypothesis. Have you ever heard of this?

I think so. Is that the idea that you can only become fluid in a language when you're young? Like there's this critical window for language learning? Yeah, it's a theory that dates back to the language. 1950s. Okay. And basically argues there's a magic window for a person to learn a first language, somewhere between age two and puberty. Scientists debate the cutoff age. But the key idea is there's a biological window where language learning is the most automatic. Where this comes from actually starts really early on with work done with zebra finches and how zebra finches and maybe even

other types of birds, but the literature that I'm familiar with points to zebra finches where early on in their development, they have to learn certain songs or calls that are particular to their kind. And these calls are important for things like mating and, you know, detecting trouble. In essence, they're important for communicating certain things that are important for their communities. Okay. And Maddie, researchers found that if baby zebra finches were separated from adults for long enough, they couldn't produce the same calls as their parents. Which isn't good, right?

When you think about how important these calls are for mating and socialization in zebra finch communities. Dang. Okay. So does the same thing happen with humans? Like, I don't know that you could ethically study that, but I'm curious. Well, there have been cases where children were denied language before puberty because of abusive parents. parents or extreme social isolation. And when many of those children tried to learn their first language past puberty, they couldn't

pick up the grammar. Gotcha, gotcha, gotcha. Okay, but how does this apply to second language acquisition in your earlier question, like how late is too late to learn another language? Yeah, this has been the big question because the critical period hypothesis has totally entered our popular consciousness as kind of this rule of. of second language learning too, that you can't really learn a language fluently when you're older. Right.

And scientists kind of disagree with this. Let's unpack why, by looking at the developing baby brain. Ooh, neuroscience. We love it. So little humans experience an explosive amount of language learning in the first few years of life. Our brain cells change over time. And that change is most rapid when we're little. Right. As our bodies produce neurological structures and connections will use.

throughout our lifetime. Researchers at the Center for the Developing Child at Harvard University estimate that in the first three years of life, your brain was developing one million new neural connections per second. Every second? That's too many. Take it easy, brain. You know what I mean? That's a lot. Baby brains got to grow. But here's the thing. Your brain doesn't stop building neural connections after you're pubescent, right? Right, right. And in the 90s and the early 2000s, researchers took note of that. They began to argue that second language learning is not bound to a biological period. How could it be?

And this idea emerged that the critical window should actually be called a sensitive window when you're most susceptible to picking up a new language. Sarah agrees with that. When we think about the critical period, we really want to think about this period of time where our brains are going through an explosive amount of growth and change. And so it's easier and even optimal to then want to learn as many things, including languages during that time period, because our brains are so quick and easy to soak up information. And once you're past that window, like me, you can still become fluent in another language.

It will just take way more conscious effort. That's the distinction. Not just. Like you're essentially rewiring your brain a little bit. Yeah, or a lot. And most scientists agree that this process becomes more difficult with age, because your body, including your brain, has already developed certain habits. And habits are hard to break. If we think about language, like, it's not just our brains involved, right? We also have to use our eyes to perceive what we see and we use our mouths. If we're oral producers of language, you know, we have to finagle our mouths to do the right things, right? And these are all habits that we've developed during our early childhood years. So once you become an adult, now you have to learn how to break those habits to adopt a new way of speaking and doing.

And so it's a little harder, but it's not impossible. It's very comforting. I hear you that I'm going to have to fight for it. Emily Kwong, you're always fighting for stuff. You're always fighting for stuff. You're a fighter. You got this. And I'm willing to fight for this one, you know?

Yeah. Like contemporary research shows there are a lot of factors that influence language learning beyond your age. There's education and exposure. and the chance to practice in your community. And I'm not going for total fluency here. I just want to know enough for my relatives to tell me how bad I am. And to be able to say, My name's Emily Kwank.

You cherelema? Which means, have you eaten? Nice. Thank you. And have you eaten is kind of a common refrain in a lot of Asian languages. It's kind of a way of saying I love you. Oh, I really love that. That's nice.

So, Maddie, in response, if you've eaten, you would say chila. Chi la. Han-Haul. Now, one area I'm kind of self-conscious about is pronunciation. So if you're listening, do not come for my tone. I already know. I already know. Mandarin is a tonal language.

And some of these tones my mouth has never made before. Right. And Sarah said that's an area where childhood speakers have a clear, unmistakable advantage. The sound system is really the first things we learn. about our languages, right? So the rise and fall and intonation and pitch and those kinds of things, as well as the actual speech sounds of our language. Those are literally some of the first things that we learn in our infancy. Which is why adults struggle to produce the speech sounds of another language. But when it comes to pronunciation and accents, Sarah kind of pushed back on my questions,

asking me, who do you imagine as a perfectly native speaker anyway? Is it fair to compare yourself to that person? I'm willing to bet that your lived experiences are going to be dynamically different from the person who you envision as your native speaker. And so you might not ever actually become native-like in your pronunciation, but I don't think that that should be something that people stress over. And the reason being is that the way that we use language fits our identity. So I can let go of the idea of sounding just like my grandparents who grew up in Beijing.

Right. Because it's here in the U.S., among my extended family and other Chinese Americans, that I long to be understood. Are you saying it well enough to be understood? That should be really the threshold upon which you want to cross. Oh my gosh. I love that. That's so comforting. This is like language therapy right now, like learning a new language therapy. Because everybody worries about that pronunciation when they're trying to speak in a different language, right?

Yeah, it took the pressure off enormously. And I should share with you, my grandma was trying to teach me Mandarin in the years before she and my grandfather died. So I feel like. I kind of owe it to them to try. Nainai, I chile. Thank you so much for bringing us a story that's as personal as it gets. Your heritage, your family, your brain chemistry. Thank you.

Thank you, Maddie. Today's episode was produced by Thomas Liu, edited by Viet Le and fact-checked by Indy Kara. The audio engineer for this episode was Alex Drewenzquez. Special thanks to sociolinguist Amelia Seng. fluent city language school, Dennis Yue Yeo Li, Megan Arias, and my family, especially Christopher Kwong, Timothy Kwong, Linda Kwong, and Amanda Kwong. This is Shortwave from NPR.