What’s the diff?

It was about 12am, and I was driving home listening to A Farewell to Kings, after having talked to a drunk all day about conspiracy theories and loss of the American Dream. I was thinking about Language and yesterday’s failure to compare languages for Lego robots. I had failed because I actually needed to have experience in programming with those languages in order to make a good comparison, I couldn’t do it without actually using the languages that I was comparing. Then, in a flash I had this idea. How can Linguists compare languages without actually using them? I suppose the just pick and choose idioms and grammer structures. But a real comparison would be a detailed, recorded history of the new constructs and pieces that a person picks up via learning a new language. This learning history would be the precise recording of the new things the person had to learn, and thus a precise recording of the differences, semantic and syntactic, between what the learner already knew (the old language) and what the learner must add to their knowledge (the new language).

So has any researcher taken this approach? My guess is that most sit in the Ivory tower that Chomsky has given them, and few have ventured forth to try and learn a new language (the anthropologists do well in this regard), and that even fewer, perhaps none, recorded, in detail, the cognitive journey of assimilating that new language. So, while many learn new languages, they don’t fully record that journey.