I agree with you. I think there are some problems with the study. For example "Does cross language interference occur?" Not only does it occur, but that's li

I agree with you. I think there are some problems with the study. For example "Does cross language interference occur?" Not only does it occur, but that's literally how you learn a new language. You make assumptions based on the languages you know. You write code. You notice that it doesn't work the way you expect. You try to understand what is different. It's by far the fastest way to learn a language rather than a problem. The learning strategies of successful language learners show this: Learning on their own, Just in time learning, Relating new language to old langue. I would say that the "Language interferences" are just a product of the learning method. Putting yourself in the deep end and trying to swim always results in a little water in you lungs ;-) The fact that it is challenging does not imply that it isn't desired. In fact there is a whole branch of skill acquisition theory called "desirable difficulties". While I think their theories of what would make the process better are interesting, I don't actually agree with their conclusion - that we should proceed as if their theories are correct.