I'm wondering what statistics, if any, are available about some of the fastest known times for the acquisition of a 2nd+ language (from zero knowledge, to some "average" level of fluency and proficiency by native-speaker standards).1

I'm specifically wanting to exclude the really odd cases of people waking up from a coma and either instantly knowing a language they had just started to study or one they had some study of before, but did not master, or one never learned, but had been exposed to.

Rather than those "instant" learning examples, what documented (or at least confirmed) cases where people set out to learn a language, and through effort, in a short time became both fluent and proficient (as note 1 helps define), and what that time frame was.

For purposes of this question, "average" level of fluency and proficiency might be considered somewhere between the conversational and low end of native-level vocabulary (based on note 1), so lets say 10,000 to 20,000 words...

Except that is still not accurate enough for some, as another comment seeks CEFR level and IRL levels. I'm somewhat flexible on this. I will take information from studies that give time frame of any level that was studied (that is, if a study exists for "fastest" time to a level, just note the level and give the time it took). However, ideally I would be most interested in studies with the rough equivalent of:

  • CEFR Level B2
  • ILR Level 2+ or 3 (2+ based on the equivalency chart to CEFR levels given on the ILR page; but the description of 3 sounds more like what I would seek)


1 As one comment pointed out, there is a difference between fluency and proficiency. I'm seeking some average level of both, and there does appear to be a relationship between them. According to Wikipedia in the "Language Proficiency" information (emphasis added):

In predominant frameworks in the United States, proficient speakers demonstrate both accuracy and fluency, and use a variety of discourse strategies. Thus, native speakers of a language can be fluent without being considered proficient. Native-level fluency is estimated to be between 20,000 and 40,000 words, but basic conversational fluency might only require as little as 3,000 words.

  • Are you counting cases of someone learning a closely related language (e.g. a German speaker learning Dutch, or an Indonesian speaker learning Malaysian) or are you more concerned with distant or unrelated languages (e.g. an Arabic speaker learning Cantonese, or a Thai speaker learning Polish)? How close is "too close"? Mutual intelligibility? – Robert Columbia Apr 24 '18 at 20:39
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    @RobertColumbia Well, I had not really considered that aspect. In my mind, I was thinking more of distant relation simply because I had not considered the case of a more related language. Information on a more distant language would be more useful to me. However, for purposes of an answer, if there is some statistics on a case of related language, that could be interesting as well (especially if in comparison to a more distant one). – ScottS Apr 25 '18 at 2:50
  • Strictly speaking, the only time anyone ever goes from "zero knowledge" to fluent, is immediately after they are born. Even for unrelated languages, simple life experience provides a lot of context which makes picking up a foreign language easier. For example, if you hear a phrase repeatedly in your new target language, you'll pick up much faster than a child that it must be referring to something in the immediate context, and will begin looking for visual or other verbal clues as to what the phrase means. – Flimzy Apr 29 '18 at 16:28
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    This question confuses fluency with proficiency; you can have fluency at any level of proficiency. See the first lines in the question What are the main types of fluency that are relevant to language learning?. – Tsundoku Jul 4 '18 at 13:30
  • @ChristopheStrobbe Thanks for the input. It seems even in the link you provided, and links in that Q & A, there appears to be no agreed upon distinction of what fluency actually means. A dictionary definition is not helpful, as it is mainly "the quality or state of being fluent," so then fluent means "capable of using a language easily and accurately" and "having or showing mastery of a subject or skill," both of which are what I meant by it. So a combination of both fluency and proficiency. I'll update my question to reflect distinction. – ScottS Jul 4 '18 at 16:56

I came across this interview by The Economist with Timothy Doner, who was a teenage polyglot (the interview is from 2013, when he was 17 years old) that had "learned" 20 languages in four years. That would translate into about 2.5 months per language (which he mentions in the interview that sometimes he only studies a language for a couple of months). However, based on his testimony in the interview, he only considers himself an English speaker, yet states he is seriously studying about 4-5 languages (taken from 6:38-7:25 in the discussion).

So from that time frame, on average, 9 to 12 months might be a target for his speed of fluency (though if some of those 4 or 5 were ones he started with, then perhaps he has been studying them for four years).

I actually have reached out to him for a statement about the fastest he has become fluent in any one language (with "fluent" being defined essentially as I did above). I'll revise my answer here if he provides more data. I supposed he is about 23 years old now.

I'm still open to documented cases of the "fastest" if someone comes up with an answer that is faster than what I've calculated here.

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I heard of an autistic savant years and years ago who could achieve fluency in just 4 days, though his ability was limited to the Germanic languages for some reason.

They decided to test him. They had him study Icelandic for four days and tested him to see how far he had progressed. They determined that he had in fact achieved full fluency within the time frame. Though admittedly, his speech wasn't exactly perfect. But this guy was autistic. Few like him can speak at all.

Tragically, I can't recall the guy's name.

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    Daniel Tammet is the guy's name. – AML Sep 10 '18 at 1:46
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    This answer would benefit from links to credible sources. – Tommi May 13 '19 at 12:54
  • It's quite likely that it's simply easier for a native English speaker to learn other Germanic languages due to the similarities in grammar and vocabulary. I would also expect, say, a similar Finnish-speaking savant to more easily learn Hungarian than, say, German or Russian. – Robert Columbia May 14 '19 at 10:47

I think that to answer your question first of all you have to consider which is your mother tongue and which is your target language. If your are Italian and want to learn French, you can achieve fluency (B2/C1) in seven/eight months studying two hours a day. But if you're Chinese and want to learn French, you should study full time for two/three years.

As a matter of fact, to achieve level B2/C1 CEFR (or ILR 3/4) you should learn all the basic grammar and at least 10.000 for level B2 (ILR 3), 15.000/20.000 words for level C1 (ILR 4): if you're learning a language similar to your mother tongue, learning 10.000 words in seven/eight months will not be an impossible task as a lot of words are very easy to guess: "information" (English), information (French), information (german), informazione (italian). However, if you have to learn it in Japanese, Hindi or Chinese, things get more complicated and it will inevitably require more time.

If your mothertongue is a European language, you can use the table of the US Foreign service institute to get an idea of the time required to achieve level B2/ILR 3, but

1) first of all be aware that maybe you can't dedicate yourself full time to learning a language or that your motivation sometimes could be low, so you should consider it will require more time;

2) second, the table just mention "class hours", so you have to add the time needed to memorize what was covered in class;

3) third, do not forget that you can do a lot with level B2/ILR 3, but real fluency is at least level C1/ILR 4, so you have to add more time.

Here you can download the Foreign Service table

Ps. I don't think it is useful to distinguish between "fluency" and "proficiency". It's true that you can be fluent when you open your mouth to ask "what is your name?" and sound as a mothertongue, but if after you can't explain what where your impressions about some news you heard on the Tv, your fluency is useless. I think we can agree that when we talk about fluency we intend the ability to talk with ease about every subject, despite sometimes being forced to use some circomlocution, that is "proficiency" in a language. Moreover, if you look for the definition of "fluent" in the Oxford dictionary, it says: "the ability to speak, read and write a language easily and well". Now, someone has claimed that you can be fluent just knowing 1.000 words: I still don't understand how you can be fluent in reading a newspaper or listening to a lecture just knowing 1.000 word. But even if you don't want to read newspapers or listen to lectures, being able to answer a mother tongue means to acquire the ability to decode sounds completely different from the sounds you're accustomed to and that requires time. With 1.000 words and three months of study you can look fluent in some basic tasks (buying a ticket, asking basic information etc.), but whenever a common situation presents something unexpected (use of new words, non standard accent, use of idioms etc.) you will be inevitably lost. Not to talk about the false impression your 1.000 word fluency can create in the person you're talking to. You begin a conversation asking a "fluent" question, the other part thinks that you are "proficient" in the language, doesn't adapt/simplify his language...and you don't understand anything. The conversation is inevitably "broken".

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    This does not answer the question. These are methods that help with learning faster, but this is not what the question is asking for. – Anthony Pham May 13 '19 at 2:22
  • I removed my own downvote as your edit of including the link to the Foreign Service Table has some usefulness to it (for "average" time taken to become fluent in various languages for an English speaker), though it still does not answer the question for "fastest known time." – ScottS May 17 '19 at 18:16

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