↑ comment by sfb ·
2011-01-12T07:31:14.849Z · LW(p) · GW(p)
For the record he says 3 months to fluency is his personal goal, not what he guarantees/claims is always possible.
There are videos of him speaking on his various blogs, but since I don't speak any non-English languages I can't judge his fluency, but I expect he is conversationally competent and not indistinguishable from a native, and yes he has to work hard at it so it's not the same kind of easy learning as children have, which seems to be what your links support, so no argument from me there.
However, he still seems to learn a useful conversational ability in a language in months whereas children take years to do that, so I still think your statement "but an adult will never learn second languages faster than a child" is a strange claim, unless you specifically mean "like a native", which seems a much stricter test than necessary.
From your links:
Probably yes: although any adult can learn a second language, not all will do so with equal results (unlike the case with child language acquisition) (first link)
One doesn't think about how every person has, or rather had at one time, an innate ability to learn a language to total fluency (second link)
Yet the results of child language learning are not equal or always total fluency - plenty of adults barely seem to know what they are saying, cannot express themselves clearly, do not finish sentences 'properly', don't notice the difference between similar words and sentences with different meanings, and people cannot orate without learning to be orators, cannot write without learning to write (I mean author well written texts instead of drivel), cannot tell stories captivatingly without practise, cannot follow official formal documents, and other linguistic things which you might lump in with fluency or might not, leading to potentially very different expectations of a fluent person.
The second link makes several comments including adult lack of opportunity (limited classroom time) which is interestingly mentioned here: http://www.fluentin3months.com/hours-not-years/