There is no such thing as being able to "learn [a] language to fluency." That's a contradiction in terms. If you've only learned a language, not acquired it, yo

There is no such thing as being able to "learn [a] language to fluency." That's a contradiction in terms. If you've only learned a language, not acquired it, you are by definition not fluent. The entirety of this Medium post is sketchy. Look at the graphs based on age of first exposure (AoFE). There is a clear stratification based on AoFE here. And yet the author concludes that "[m]any late learners become native-like." Why? The linchpin of his argument is that some non-native English speakers scored better on a quiz than some native English speakers. But wait a second. That's mistaking error and fault (or competence and production). It also assumes the quiz works across English dialects, or that it actually measures fluency. But the author even says: "This test is not about fluency, it’s about highly pedantic grammatical accuracy." And even if we construe all those factors in favor of the point the author is trying to make, the top quartile of late learners will still never reach the competence of those who started before age 10 (except, potentially, briefly while the latter is still a kid). Most troubling is the anti-intellectual dismissal of "some magic change in brain plasticity." Changes in neuroplasticity with age are well-established. The change is, in fact, so stark that people worried for a long time that we completely lost brain plasticity in adulthood. Even a cursory reading of an overview of neuroplasticity is sufficient to understand how wrong-headed the author is: https://en.m.wikipedia.org/wiki/Neuroplasticity https://en.m.wikipedia.org/wiki/Neuroplasticity At the end of the day, the test doesn't measure fluency, it measures the ability to answer questions about the prescriptive grammar and writing style. Even so, it largely supports the LAD hypothesis, with clear stratification based on the age one begins learning a language. The author of this blog post misunderstands the applicable linguistics and dismisses established neuroscience out of hand. His opinion should be given no weight.