How Do You Learn a New Language, Without Forgetting the Old One?

The biggest difficulty I had when learning Spanish was, perhaps surprisingly, speaking French. I had learned French to conversational fluency before learning Spanish. However, as my Spanish got better, I found it made speaking French much harder.

The problem got so bad, that after only a week or two in Spain, I could speak better Spanish than French. That’s not because my Spanish was great—I still couldn’t perform even basic functions like the past tense—but because every time I spoke French I’d stall on basic phrases and accidentally use Spanish words.

This, of course, presents a serious problem to someone like me who wants to learn multiple languages. What’s the point of learning a new language, if your previous one gets overwritten in the process?

What’s Actually Going On?

Given I’m going to be tackling four languages in a short period of time, this was definitely a problem I wanted to research. It turns out to be quite a common problem for adult learners of multiple languages.

My suspicion was that the French wasn’t lost, it was simply being dominated by my more recent Spanish. When I’d look for a word, the Spanish one came up and made it harder to retrieve the French word. Instead of being erased, my French had a layer of Spanish piled on which I had to dig through first.

Another bit of evidence with that hypothesis was that my ability to speak was impaired considerably more than my ability to understand French. This makes sense: when hearing a French word, I need to remember a connection between those exact sounds and a concept—something unrelated to my Spanish. However, when speaking, I need to go from a concept to a set of sounds, the correct responses in English and Spanish compete with French, making speaking harder.

For example, hearing the word “aussi” triggers my  memory of the word “also” in French automatically. However when I try to say the concept of “also”, I get the word in English, obviously, but also the word in Spanish “tambien” which slows my ability to retrieve the French word somewhat.

I also found that my writing ability in French wasn’t impacted nearly as much. Again, this supports the same hypothesis because writing allows longer time to reflect over which word to use. Allowing longer reaction times meant I could push past my Spanish interference and get at the correct word, which would have broken my flow in a speaking situation.

Restoring my French

This hypothesis implied that I could restore my French simply by speaking French for an extended burst. That would bring those buried French linkages back to the surface so they wouldn’t have to compete with my Spanish.

I tested that hypothesis by taking a week to visit France and speak only in French (luckily only an inexpensive train ride away from Spain). And, despite the initially bumpy start, things became easier until by the end of the week until it was only a little worse than my prior ability. I made a few more mistakes and had some tip-of-the-tongue moments, but otherwise I regained my ability after only a few days.

Upon coming back to Spain, I found myself tripping a little bit in Spanish, but to a far lesser extent than I had noticed in French.

Observations and Switching Costs

Beyond my personal experience, I’ve also made some informal observations about how this problem seems to affect other language learners.

First, it seems to affect you less when your language ability is higher. My French was an upper intermediate level when I last left France, but not at the point of mastery. Learners I’ve met who speak at nearly bilingual levels don’t seem to suffer the overwrite problem as badly. I think this is probably because the correct words are imprinted so automatically that they are very difficult to bury beneath a new language.

Second it seems to affect people engaging in complete immersion more. Because I spoke almost entirely in Spanish for the better part of three months, I wasn’t learning how to switch between French and Spanish. Had I learned in an environment where I still needed to use French frequently, I would have learned that skill as my Spanish improved.

Thirdly, it seems more of an issue the closer the languages are. People who have learned to very different languages seem to suffer from interference less than two similar ones. This is particularly relevant to me because Portuguese, my upcoming language, is very similar to Spanish.

Finally, switching costs seem to diminish the more they are practiced. Believe it or not, my French actually suffered the most at the beginning of my trip in Spain, despite Spanish only having a small amount of time to form an impression. Even the small amount of practice in French I did seemed to make switching easier.

Potential Solutions to Language Switching Costs

I can’t say that I have this problem solved yet, but I do have some strategies I’m hoping to use in the next three countries.

Benny Lewis suggests some solutions here that are worth exploring: namely practicing switching and using your body language to reinforce the distinctions between languages.

My feeling is that part of the problem I faced with French was that I was learning Spanish, but I wasn’t learning the necessary skills to keep it separated from French. For example, I had learned “il y a” => “there is” when I learned French, and “hay” => “there is” in Spanish, but I hadn’t learned NOT to use “hay” => “there is” in my French.

This suggests that the best way to avoid switching costs is to practice switching. In some senses, this means “re-learning” a bit of your previous language in order to keep it separate from your current one.

My Plan for Portuguese, Chinese and Korean

Given I have three more languages to learn, and I certainly don’t want to end the trip with each language having replaced the one preceding it, I think practicing switching will be essential to maintain all of the languages.

Since switching costs seem higher in more similar languages, I think this means Brazil will be the country I’ll need to put the most emphasis on. My plan is to do an hour or two of tutoring every week in both French and Spanish, in addition to my Portuguese. That should give me practice switching while I learn the new language.

With Chinese and Korean this might not be possible—the amount of work to reach an acceptable conversational level might be too high. If so, this will mean switching costs will be something I’ll have to practice on when I return to Vancouver.

Fortunately, more similar languages are easier to learn, but harder to keep separated. That means that if Brazilian Portuguese is significantly easier than Chinese to learn, I’ll have more time to focus on maintaining that separation. Conversely, if Chinese is harder to learn, it might also be harder to mix up.

Does This Mean You Shouldn’t Learn More than One Language?

The decision to learn one language extremely well or a couple languages to conversational abilities depends on a lot of different factors. If you’re interested in traveling and speaking with locals, I feel a rough conversational ability can get you most of the way. If you’re looking to live and work in a single language, then mastery is often worth the investment.

True mastery also dwarfs switching costs in terms of time investment. A decent conversational ability is perhaps 10% of the work of reaching a mastery level. Switching costs may make learning multiple languages harder, but it is still considerably less work than mastery. But it does mean that, if you plan to learn multiple languages, that you should have a plan in place to keep them separate.

What are your thoughts on the switching problem? If you’ve learned more than one language before, did you experience moments where you got them confused? What was your solution? Share your thoughts in the comments.

  • Natalie

    Interesting thoughts, Scott. I definitely agree that the closer two languages are, the more likely one is to confuse them. However, in my case, there seems to be an interesting exception to this rule. Learning Serbian messed up my Russian so much that I eventually had to stop learning it. Ukrainian and Belarusian, two Slavic languages that are closer to Russian than Serbian is, do not confuse me nearly as much. In fact, I’m pretty good at keeping them separate. It’s a very strange phenomenon.

  • John

    Hi Scott,

    I agree with the ideas you proposed in your article. I speak English and Portuguese fluently and Spanish at a conversational level. I find that I often mix up Portuguese and Spanish words, but I can easily keep Portuguese and English separate.

    Along the lines of what Benny’s advice, I also think that the language your brain associates to a specific environment is very important. So learning Portuguese in Brazil will be a lot easier than trying to learn Portuguese in Spain.

    Good luck in your project!

  • Jefferson

    Hi Scott,

    Awesome thoughts.

    Actually, this problem is kinda simple. Let’s take a look at me for example. I’m from Brazil, then I speak Brazilian Portuguese since I was a child. Everytime I need to go to another country for some reason, I take few days (usually two weeks) to get used to the way local people way of speaking. English is my second language, so I took two weeks to get used to the American way of speaking english. Now, I’m currently living in Ireland. I’m here for two months, and I still have trouble with some people who have a strong Irish accent.

    The way back to Brazil will also be overwhelming despite my nativeness because I had to change the way I named everyday things. Of course, the adaptation will be quickly.

  • Michael

    Nice post Scott. After learning Spanish to C1 level over 3 years, I had 3 weeks of immersion in Cameroon. When I had a Spanish lesson of Skype in middle of my Cameroon stay, it was surprising the amount of interference from French I had – especially with small words like “avec/con”, “fois/vez” even “oui/sí”!

    If we call our native language L1, second language L2, and third language L3, I think your theory of learning NOT to use words L2 words in the L3 definitely has merit. For me my L2 (Spanish) seems to continue to have more interference from French (L3) than vice versa, even though my Spanish level is way higher.

    Good luck with the next upcoming challenge where I’m sure you can provide us with more experience in this area with your L4 (being very similar to your L3)!

  • Berkan

    After learning English through games and movies, which took around a couple of years. I indeed have moments that I want to say something, but only know how to say it in English. Even though Dutch is my native language.

  • Paul at “No Pension, Will Trav

    I’ve definitely experienced this problem. The first language I learned well was German. Although I had some French & Spanish background from school, I didn’t really speak them. Then I went to Brazil and things got really confusing. Early in that trip, I connected with some Spanish speakers. Surprisingly, what I’d learned in my Portuguese helped my ability to speak Spanish, but also blurred the distinction between the two languages. Since that day, I’ve always spoken Portuguese with somewhat of a Spanish accent. Years later, when I worked on really learning Spanish, I found I could never shake the habit of throwing in a lot of Portuguese words. The two languages have a lot of similarities – in fact you can often guess at words in one by doing regular “sound shifts” from the other. While this is overwhelming consciously, I’m wondering if the brain actually does this semi-automatically if you just get in the right “mindset” – I agree with you, that trying to mimic the facial and body gestures, and in particular, the musical cadence helps with this. (Brazilian Portuguese has a very particular cadence, very different from Spanish – more precisely, there is more than one – my cadence marks me as having learned my Portuguese in Rio.)

    There are funny things that can arise from all this. My first hosts in Rio were Brazilian Jews, and they actually spoke Yiddish at home, a language with some similarity to German. When I was searching for Portuguese words, and German popped out, they didn’t even blink, and we just kept right on going!

    The only real conclusion I’ve drawn is the better you know the language you’re trying to speak, the less likely the other languages will intrude. It seems to be when you’re searching hardest for words that this mental crosstalk seems to occur.

    This effect also seems to occur when I switch into a language I haven’t spoken for a while. At first I’m searching for words and they come up in the wrong language – after about three days of continuous immersion (my rule), the effect seems diminished. I imagine, but don’t know, that the more you switch back and forth, the easier it will get.

    Still, listening to native non-English speakers around me in Vancouver, their speech often seems peppered with English words. At some point, maybe we all do this, and as long as we understand each other, it works!

    However, when these non-anglophones include anglicisms in their speech, they do it with the musical cadence of their own language. I think musical cadence may be the key to waking up the appropriate brain centre, and maybe you can experiment with this. I’ve actually written a couple of posts about my own language learning experience, most recently on my current blog, and there is a link in that one to an earlier post where I reflected on the musical aspect of language learning.

    PS. Which Chinese will you learn? While I only know a few words of Mandarin, my initial reaction is that it would be harder for me than Portuguese. Perhaps it’s because it’s musical cadence is so very different from any of those I’ve learned to date. Closely related to musical cadence of language is the music that comes out of that linguistic culture. Again, for most anglophones I know, Brazilian vocal jazz is more accessible than Chinese ballads. I suspect there is a connection here.

  • Wanda

    Even though I just visited your page (via 99u), I felt very proud that you decided to learn four languages… That’s way more than most American born even think it’s a possibility.
    My experience with languages:
    1st of all, stop tripping. Languages are meant to open communication with others and you certainly don’t need to be an expert or always have the right word at the tip of your tongue. Not even single language speakers have that. 2nd, bilingual babies take longer to speak because speaking languages take more brain effort. The brain will let go of the word that it associates with first, whatever the language.

    I am a native Spanish speaker and became fluent in English by doing a full immersion– TV, books, friends, speaking with strangers– to the point where I decided to stop bc I wanted to keep my accent. Along the way, I found that studying Spanish improved my English. Then, I learned French is college. My English became better. (I belief because it helped me appreciate language and I was exposed to more words.)

    I learned Italian by staying in Rome-Arrezo for one month. I used a lot of Spanish & French to open my brain up, and added new Italian words as I heard it spoken around me. By the end of the trip, I was less dependent on other languages.

    I returned to Italy three years later– I didn’t study it in between, though I did watch a few movies and gave NYC directions to a few tourists. Upon arrival, I spoke lots of Spanish, French, some English while sprinkling in some Italian. I really wanted to speak Italian and after two days it came back to me. My French, btw, much better.

    I regularly switch from Spanish to English and I still find myself saying a Spanish world in an English conversation and vice versa. You don’t loose the language, it just gets filed to the back of the brain.

    What I enjoy the most is speaking with my multi-lingual friends, bc I can just let go and speak 2-4 languages in one sentence. Try it some time. It’s awesome.

  • Sam

    There’s a concept called “laddering” where you learn a new language with a different language as the “base”. So say your native language is English, you learn French using English; then to learn Spanish, you use French to learn Spanish; and then use Spanish to learn another language and so on. Thus, theoretically, if you never use the same “base” language twice, it will be harder to get the languages mixed up.

    I’m not sure how this would work for immersive situations where you only use a single language. However, for using languages as the base, I would assume that it would work more effectively if the base language is not similar to the new one.

  • Matt

    My observations on this topic, which i find fascinating:
    even languages that appear not to be similar are easy for me to confuse. i’m fluent in spanish and spent two months in an intensive mandarin course, roughly 50 hours a week of classes and activities. virtually all single syllable common words in spanish have a mandarin homophone, or something close to it, making it really easy to confuse the languages. that was a big surprise for me although it shouldn’t have been.

    the brain is much more likely to swap certain gramatical categories of words than others. i think this would make a great topic for linguistic research because it would probably reveal something profound about language processing. someone already mentioned this but it’s much much more common to have persistent swapping in closed-set grammar categories (words like pero, si, tambien, mas, por, tampoco, etc) than in open set categories (nouns, adjectives, verbs). this even happens with my L1 (i spend most of my time in mexico but when i visit the states and speak english i often inject spanish conjunctions or fillers into conversations). it’s a very weird feeling.

    good luck with your project, i’m really looking forward to reading about brazil.

  • Celestral

    Oh this is a nice post for me!
    I have exactly the same problem but with two very different languages.
    I mix Japanese and French all the time. When I need to speak French (like a few weeks ago when I was with family) I had a lot of difficulty not saying things in Japanese. At least in the first few days. By the time I recovered, I had difficulty thinking of Japanese words.

    I don’t have this problem with my limited German at all. I guess French and Japanese are similar to my brain? Or maybe it’s because German is very similar to my native language (Dutch).

  • Isabel

    Thanks for the post, finally I don’t feel all alone in this confusing world of learning languages. I stayed in Mexico for 10 months 6 years ago and so my Spanish proficiency was almost at the native level. During all those years, I think I kept it to a decent level, despite not talking regularly in Spanish. However, last year I moved to Italy. I tried (not too hard but I tried) to learn Italian but had and still have huge difficulties (understand everything, but talking is almost impossible!). At the same time, my Spanish is GONE. I had to write a wedding card for a Mexican friend of mine yesterday and almost wanted to cry, since without google translate I would’ve not been able to. I really wish there was a solution for this (I guess it’s practice practice practice…but who has time for that!?). Good luck for your upcoming language challenges!

  • Ramon

    This is a very interesting topic for me Scott. I am learning Spanish while leaving in Buenos Aires but I do often travel to Brazil for my work trips. I experience the cross overs in the words when I try to converse in Portugese but I get by. By the way, I will be going to Florianopolis this December and I would love to meet you and Vat while I am there if possible. Thanks and Goodluck.

  • James

    In my AS year of secondary school (age 17) I was learning French, Spanish, Italian and Japanese at the same time. At the start of the year my Spanish was around B1, French at A2, Japanese at A1 and Italian from scratch. It was a nightmare at first – French, Spanish and Italian are so similar that I constantly got confused between them and my Italian skills were minimal so my brain hadn’t created an ‘Italian box’ yet. Japanese was more easily separated because of the significant differences, although it does contain some European loanwords like アルバイト (arubaito) meaning part-time work, from the German ‘arbeit’ meaning work. I also had three classes taught in my native English so I was switching between five languages at the drop of a hat multiple times a day.

    It was definitely being thrown in the deep end of language switching and by the end of the year I was a lot better at it. My switching is still not infallible but I had to get fairly good at it in order to pass the relevant exams – I’d be lying if I said this sort of intensive insanity was not partly motivated by my impending university application the next year. It’s a skill that comes with practice and I think as your level improves you get into more language-specific vocabulary and grammar which makes them easier to separate. Keeping your Spanish and French ticking over while you’re working on Portuguese is a good plan, maybe have a book on the go or watch a news programme regularly so you’re still using them while focusing most of your energy on Portuguese.

  • Miriam Hoelker

    Hi Scott!

    I know that problem. I always switch to that language which I can speak a little bit better than the language I want to use. The ranking of my languages is: German (native language), English, Russian, French. That means when I want to speak Russian, english words come to my mind and when I try to speak French I mix it up with Russian (but not English). A few years ago, when my French was better than my Russian, it was the other way round. So in my case the level of my knowledge seems to be more critical than the similarity of the languages.

    Practice switching between the languages sounds interesting. I’ll try that!

  • dag

    I also came across the problem you describe while learning German and Dutch. I’m sorry to say that there’s not an easy way to solve it. I also try to learn as many languages as possible since I started seriously studying English a bit more than two years ago.
    In my case, I decided to keep improving my German while getting stuck at Dutch. The latter is a beautiful and interesting language to me and I intend to resume it when my German is more developed so that the risks to mix them are not so high.
    Anyway, you shouldn’t expect too may troubles in tackling Chinese and Korean since they are different enough, but you must fear Portuguese. It is SO related with Spanish and French that learning it will painfully challenge you.

  • Julia

    Hi Scott and previous comment posters,

    I often read the articles on this blog and identify myself more or less with them, but this one definitely got me thinking. For many years now, I’ve been very interested in the problem of speaking several languages and have been on the lookout for scientific studies on that topic. I would also enroll for one in the blink of an eye but haven’t yet encountered an opportunity to do so. Like you, I have to satisfy this interest with empirical observations and with my own experiences, which is captivating but not always very objective.

    I grew up in a bilingual home, in which my parents spoke different languages: French and Dutch. My parents usually spoke to us (my sisters and I) in their own respective language, but family conversations were a melting pot of both languages, though we would rarely mix languages in one sentence. In school, I also learned English (up to bilingual level) and German. In my free time, I taught myself Italian (ah, the power of teenage love!).

    The most striking thing I’ve noticed so far is that I have two very strictly separated “boxes” in my head for each of my native languages. The content of those boxes rarely gets mixed up and I almost never come up with Dutch words in a French conversation or vice versa. Also, once something or someone is in one of those boxes, it is very, very difficult to move them out of it. To me, Harry Potter books are French because that is the language in which I started reading them. I tried switching to the English books but it felt too weird, it wasn’t the same story anymore. Same thing with people: I will have tremendous trouble talking to my parents in a language other than their own, even if we are in an international setting. It is far easier and more natural for me to talk to them in either French or Dutch and then translate what I said to the other people taking part in the conversation. As you explain in your post, the separation between my first languages is mostly on the level of words, not on that of concepts. This means that I sometimes use a Dutch saying or expression in French and then understand by the look on the faces around me that this expression did not make any sense to anyone else but me.

    When it comes to words though, French and Dutch never get mixed up. When I speak English for example, I might use a French word by accident, especially when I’m tired or just had another conversation in French. The opposite is also true: I might use an English word in a Dutch or French conversation after a long period of speaking only English. I will never, however, use a French word in Dutch or vice versa. If I can’t find a specific word in one of my native languages, I will often find it in English. Say I’m looking for the Dutch word “fiets”; the English word “bike” is very likely to pop up in my mind, while “vélo” most probably won’t.

    Switching and bumpy starts. I definitely recognize this, and it happens to me with my native languages as well as the ones I learned later in life. It usually takes me from a few hours up to a few days to get full access to a language. It’s like my brain can only use a certain amount of memory for linguistic purposes at a time. When I fly back to the Netherlands for example, I have the “basic native speaker level” for a few hours and then my brain gradually puts English in the background, takes the box labeled “Dutch” off the shelve and pours its content all over me. Because they are so deeply rooted in my system, French and Dutch recover faster than the other languages. I have to mention that since I’ve been living in the US, my English is slowly getting to the same level as French and Dutch; in my brain that is. There is no box for English yet, but the bumpy start effect has become less and less in English. Most people here also tell me they don’t hear any foreign accent when I speak (so long, cute European accent…). I also agree with the observations that the more regular language switches are, the easier they become. Down to seconds to get full access to a language when I’m traveling a lot or when I’m at an international party (though having had a few drinks also helps ease the transitions).

    Another thing I experienced and found fascinating is passive storage of a language. I attended French-speaking schools until I went to college and used my Dutch for speaking (mostly to my dad), listening (again, mostly to my dad) and reading (we had a rule at home: any reading after 8 pm had to be in Dutch. Very good rule, it paid off!). Writing in Dutch only happened on rare occasions and at low levels of difficulty: postcards to friends or crosswords were the two main options. I never wrote an essay or exam in Dutch. And then I decided to go to college in the Netherlands. Honestly, the only thing I was afraid of when going to college was that my written Dutch would not be good enough. First semester, first essay (and not a very inspiring topic). I stared at my computer screen for a bit and then started writing. I wrote the whole essay at once, just typing the sentences as they came, and sent it to my dad to have him check the spelling and grammar. He told me I had a few spelling mistakes here and there and one or two sentences were a little too verbose, but I had a good writing style and that was the hardest thing to get right when writing essays. Basically, I didn’t do worse than if I had had to write the essay in French or English. Now the most interesting thing was the feeling that came with writing that essay. All of those words and sentences had been stored somewhere in my brain; I had collected them from books, tv shows, conversations, newspapers… Everything I had read or heard in Dutch had been meticulously put into a box and stored for later use. You never know, it might come in handy. It took a few minutes to find the dusty box in the back of my brain (hence the staring at my screen) but once it was available, its content just spilled over my keyboard and tadaa, there was the essay.

    The last point I’d like to react to is about something that you and most other posters share: the experience that the closer two languages are, the more likely you are to confuse them. In my case, I’ve had the opposite experience (and I am curious what Natalie’s native language is?). I sometimes confuse words in French and English, or Dutch and English, especially in writing (“apartment” in English and “appartement” in French, those damn p’s). However, I never get confused when it comes to Dutch and German or French and Italian. I think this is because in each of those cases, one of the languages is my first and the level of imprinting is much higher, although I would expect that to also be the case with English and French or English and Dutch. Maybe after I’ve stayed a few more years in the US.

    I think the most interesting thing about learning new languages is that the deeper you get into it, the more you understand about the culture surrounding it. Some words and concepts really only exist and make sense in a certain language. I’m curious if you will find some of those words and concepts during your year without English.

    I hope you will keep enjoying your travels and linguistic experiments and I’d be happy to read more about your experiences on this topic.

    Best of luck!

  • Ben

    Very interesting Post. I’ll recommend it on my blog.


  • Marly

    I think this challenge is great, but I do question attempting 4 languages in such a short space of time.
    Because in a couple of years time, your level in all 4 languages will be poor.

    I think quality is more important than quantity.

    I am myself a native French speaker. I Learnt English and Spanish at school and have lived in the UK all my adult life.
    I then lived in Spain for one year which helped with my conversational Spanish.

    Now, maintaing the languages I do not use daily (Spanish and French) requires efforts.
    I read books and publications in these languages and thankfully I have French and (one) Spanish friend.

    What I found is that a lot of my vocabulary in either languages become dormant if I don’t practice.

    So i’m not sure whether you’ll manage to maintain a good level of your four chosen languages overtime.

    Then again you seem to do challenges for the sake of doing a challenge as opposed to the actual benefit of learning.
    You had no intention of pursuing an engineering career after the MIT challenge.

    To me languages go far beyond vocabulary and grammar.
    They are the best way to truly understand a culture, its history, its traditions, its music, and its people.
    To me speaking foreign languages have opened me to so many things. And I do feel now that I belong to England, just like also, I belong to Spain. And to France of course, my native country.

    Have fun in your trip!

  • Juan Cazador

    I learned Spanish in 1989 and have native fluency now.
    In the last 25 years I have studied Russian, Arabic and French and in order to not lose my Spanish skills I studied those languages through Spanish. I bought books and language courses meant for Spanish speakers, and in this way I am using Spanish to learn the 2nd, 3rd and fourth languages. It conserves my Spanish skills while furthering my knowledge in other languages.

    Try it.

  • lemon

    Cause now I have just mastered Chinese(native) and English , I don’t find any confusion between the 2 languages . Now I am studying Japanese ,cause Japanese has the most similarity to Chinese ,I can learn it very easily . What I concern to your confusion between 2 similar language is that ,why you don’t learn the other language compare to the similar one you have master ?