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).
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.