Language shift?

http://en.wikipedia.org/wiki/Communication_accommodation_theory#Convergence
http://www.putlearningfirst.com/language/04change/differences.html

Thank you for your reply, sir.

Just to be sure if I understand it. So, if we have two dialects A and B from two tribes A and B, and people from the A tribe shifts to the tribe's dialect B, in this case we can say that language shift is related to tribal association, isn't it?

As I understand it the shift is usually in the direction of "social expedience". I assume what you mean by the term "tribal association" is that a socially dominant tribe absorbs another tribe such that the lesser tribe adopts the speech habits of the dominant one. In "class terms" rather than "tribal terms" a good example is the former trend towards RP (Southern/upper class/Oxford English) over regional (working class) dialects adopted by those wishing to be "upwardly mobile".

For a historical/tribal discussion I suggest you research "isogloss" which involves territorial dialect boundaries associated with historical conflicts between cultures.

I think I got it. I will see that.

Thank you so much.