If A learns to play the piano starting at age 5 and B starts at age 35, I wouldn’t be surprised if A is not only on average, but almost always, better at age 25 than B is at 55. Unfortunately, that’s basically impossible to study while controlling for all confounders like general intelligence, quality of instruction, and number of hours spent on practice.
If all you are saying is that people who start learning a language at age 2 are almost always better at it than people who start learning the same language at age 20, I don’t think anyone would disagree. The whole discussion is about controlling for confounders...
Yes and no—the whole discussion is actually two discussions, I think.
One is about in-principle possibility, the presence of something like a critical period, etc. There it is crucial for confounders.
The second discussion is about in-practice possibility, whether people starting later can reasonably expect to get to the same level of proficiency. Here the “confounders” are actually part of what this is about.
If all you are saying is that people who start learning a language at age 2 are almost always better at it than people who start learning the same language at age 20, I don’t think anyone would disagree. The whole discussion is about controlling for confounders...
Yes and no—the whole discussion is actually two discussions, I think.
One is about in-principle possibility, the presence of something like a critical period, etc. There it is crucial for confounders.
The second discussion is about in-practice possibility, whether people starting later can reasonably expect to get to the same level of proficiency. Here the “confounders” are actually part of what this is about.