My degree was in linguistics (although it is not my current profession), and I wholeheartedly agree with your comment. My personal opinion is that claims of po

My degree was in linguistics (although it is not my current profession), and I wholeheartedly agree with your comment. My personal opinion is that claims of polyglotism are quite often (if not usually) exaggerated, whether intentionally or not. There are many different metrics for language proficiency, but they are all just samples of a person's linguistic competence rather than a complete picture. For that reason, they're prone to the same issues as general intelligence tests. A high score on a language test is no guarantee of fluency just as a high IQ is no guarantee of intelligence-- and this is all assuming the person claiming to be fluent has even taken such a test, which is rare. I think more often people have individual standards for "fluency", which vary wildly. Again, I'm not saying that people intentionally mislead others about their own language ability, or that there aren't any true hyperpolyglots-- just that such claims should be taken with a grain of salt. Both the description of the critical hypothesis in the article and the person who described it as "a bunch of crap" are wrong. The hypothesis actually states that there is an ideal window for language learning that occurs at a young age, whereas the article presents it as "a narrow window during childhood in which we can pick up the nuances of a new language". No serious academic linguist that I have ever met subscribes to a definition that rigid. Adults absolutely can pick up on the nuances of a new language, but for the overwhelming majority it takes considerably more time and effort compared to a child in the critical period. I do believe that language learning for adults can be made more efficient than it usually is (e.g. the classic cookie-cutter layout of every foreign language textbook I've ever read), and perhaps some of the strategies laid out in the article are effective, but that does not discredit the critical period hypothesis and it's still going to take a lot of effort for a typical adult to become fluent in a new language.