I've seen advanced graduate courses for languages, in which the level of the language itself is higher than average for the average native speaker. I was wondering if there was any research on whether it would have a different effect on a native speaker versus someone a second language learner.
For example, if a native Spanish speaker from a Spanish-speaking country chose to improve their Spanish skills, would the effect of the same method be different from a second language learner?
Or would the disparity in each individual's learning effectiveness make this ordeal trivial?
I'm using English and Spanish as examples for the question since, according to this article, Spanish has a Category I ranking of difficulty for Spanish speakers. I do believe the question still stands for native speakers of other languages since the question is for people who are around the same level of Spanish before taking the advanced classes.