Second languages and selection bias

When I was growing up, I was told that you could never become fluent in a second language, and I believed it. I had no reason not to. I didn’t know anybody who had become fluent at a second language, and I could think of plenty of people who had learned English as a second language but who weren’t fluent.

But how would I know if someone had learned English fluently? If they were fluent, I’d assume they were native speakers. I knew people had learned English as a second language because they weren’t fluent. This is selection bias, where the selection of data you see is influenced by the very thing you’re interested in.

A famous example of selection bias is that of British bombers returning from missions over Germany in World War II. Statistician Abraham Wald advised the RAF to add armor precisely where these bombers were not shot, reasoning that he was only able to inspect bombers that survived their missions. More on this story here.

When I was in college, I had a roommate who had learned Spanish fluently as a second language. I thought “That’s not possible!” though of course it is possible. I immediately began to wonder what else that I thought was impossible was merely difficulty.

13 thoughts on “Second languages and selection bias

  1. For the 18 first years of my life, I believed that no foreigner could speak French fluently. By that, I didn’t only mean speaking with no accent at all, but also selecting the precise tone and a natural choice of words. And then, one evening I saw Jodie Foster interviewed in French on the most popular TV channel in France. I still refused to believe it, wondering who was that French actress who looked like Jodie Foster to the point of confusion. I had to see an overlay on the screen to admit the truth. I had my counter example. For years after that, I shared that epiphany. I encouraged my foreign friends to pursue their linguistic efforts and never give up on French.

    And then, one day, I checked Wikipedia: “Foster was a gifted child, and learned to read at the age of three. She attended a French-language prep school, the Lycée Français de Los Angeles.” The French version of Wikipedia even states that she did all her education in French speaking environments. So long for using that one sample as an example…

  2. In this field that we find ourselves I very often hear some version of the phrase “I’m too old to learn language/process/paradigm/framework/tool ______.” I find that those very people are usually technically and experientially well positioned to learn a new skill. I don’t know if this is an example of selection bias, but it’s definitely an example of a phrase akin to “what else that I thought was impossible was merely difficulty.”

  3. Mathiru: Based on my experience, I’d say your original belief about the impossibility of learning French was correct. 🙂

    When I was in France, I tried to initiate conversations in French, but everyone mercifully replied in English.

    Fogus: “The man who is too old to learn was probably always too old to learn.” — Henry S. Haskins

  4. I found just the opposite in France — people were happy to speak French to me. It seemed that fewer people spoke English in France than in other European countries, and those French who did speak English were less fluent than other Europeans.

    I freely admit that this is a gross generalization though, based on about five weeks total spent in Paris and Lyon.

  5. There are lots of studies about bilingualism (my own children are bilingual, my wife is Spanish, we speak Spanish at home, but we live most of the time in the US, my nephews are also bilingual, they grew up in Spain, but spent summers in the US, and full years in (5th grade, 9th grade for all, and also 10-12 and college for the eldest of the 3)
    The studies I’ve read seem to indicate that you really need to learn at least the sounds of the other language(s) by age 7.

  6. I’ve never studied linguistics, so anything I say about linguistics is second-hand. But I have several friends who have studied linguistics and their opinion/experience is that it is possible to learn the sounds of any human language as an adult, though it takes a lot of hard work if you didn’t grow up with those sounds.

    It’s fuzzy to say when someone is “fluent” and there is controversy about just how fluent someone can be in a second language learned as an adult. But certainly many people have achieved a very high degree of fluency, higher than I thought possible.

  7. John,

    It is possible to become fluent later in life but it doesn’t happen often. I know because I’ve done it and so has my brother who speaks fluently in two other languages besides English. The reality is that you need to immerse yourself in a language if you wish to become fluent; otherwise, you won’t be able to overcome the difficulties of pronunciation (i.e., and this is the hardest one to overcome) and your ear will never become adapted to all the nuances of the language. Just like Americans have accents depending on where they’re from within the United States, so do languages. It’s definitely effort-dependent but doable. It’s amazing what a person can learn in terms of languages if you submit yourself into the environment. I watch quite a bit of film in other languages as well and this helps greatly with pronunciation and hearing.

  8. Johnathan Corgan

    I have an interesting N=1 anecdote. My mother was trilingual (English, Castillian Spanish, Italian), and my father English only. For whatever reason, they decided to speak English only to me and my brothers growing up.

    However, we often hired live-in domestic help, which invariably were Latinos from a variety of places in Mexico and Central and South America. My mother would speak in Spanish to them, and we would of course overhear these conversations.

    My parents divorced when I was 11, I lived with my mother, and decided to learn Spanish. In about six months, I could read, write, and speak, although with a limited vocabulary. Curiously, however, I had no difficulty with pronunciation, and natives would comment that I sounded like a Spaniard that had lived in Mexico a long time.

    I don’t use Spanish very often anymore, and easily lose my “fluency”. When I travel to Spanish speaking countries, however, after several days, a switch flips, and it comes back.

    So, that early exposure to the language appears to have made a big difference, though the delayed formal learning prevented it from becoming effortless.

  9. Jonathan: I’m sure it helped to have heard Spanish growing up. It’s also easier for an English speaker to speak Spanish without an accent than the other way around. Spanish has fewer vowel sounds than English, and the ones it does have are not far from English counterparts.

    If I remember correctly, English has 17 vowel sounds. (So much for the 5 long and 5 short we have in theory!) There’s a way to objectively plot these sounds on some sort of two-dimensional grid. Some of our vowels are very close together (like the sounds in bid and bed). They don’t sound so close together for native speakers, but they’re very difficult for other people to distinguish.

  10. My mother when she was at uni, studied French for 3 years.
    When my parents relocated to France, although she had the best grades in her class couldn’t interact with people.
    After spending a year learning on her own and interacting with people she managed to master it. Her only trouble is not being able to pronounce ‘r’ and ‘x’s properly.
    Still, when speaking in English or in French both of her accents are proper, unlike myself.

  11. We should not mix up the property of being indistinguishable from a native speaker with the property of being fluent in a language.

    I firmly believe (and have seen/heard) people become fluent in German. It is possible, even for adults. I would consider people to be fluent in a language when they rarely make mistakes, can express themselves as comfortable as in their own language. If they make mistakes, they are in rarer cases of grammer or vocabulary.

    Becoming indistinguishable from a native speaker is way harder. There are the tiniest of details that non-native speakers are not even able to hear, and even more so not able to pronounce. In the end, the question is whether becoming indistinguishable from a native speaker is really one’s goal. Becoming fluent in a language is enough, and it is possible, given effort (and probably the time and energy to immerse oneself).

  12. I agree that it takes a lot of hard work, but it is certainly possible to become fluent in a second language as an adult.

    Growing up with two languages is relatively easy. My father and his siblings all did this, and were all perfectly – natively – fluent in both Mexican Spanish (not what they teach in schools) and American English.

    But that’s growing up with it. For learning as an adult – when I was in the Air Force I learned about the Defense Language Institute in Monterey, CA. From what I heard, this place turns out people who can speak well enough to fool a native speaker in many languages. But it takes a lot of full-time immersion in the language.

  13. Quick follow up to your French anecdote in France John. I’m fluent in French (from Montréal, Canada) and when I go to France they sometimes reply to me in English only because on the accent disparities… 😀

    But growing up in Québec and living now in Montréal for the last 10 years, I know a lot of people who are fluent in both French and English. But I guess you have to move to another country to perfect it or live in a place where you can speak multiple languages through the day without problem. (And I guess some people are better than others to learn and adapt to a new language)

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