I'm not sure if this is too vague for you, but Henry Petroski talks about it in his book (google books excerpt). It kind of boils down to efficiency in picking up food without being too large or broad for the mouth, again, but it does relate to the changing function of forks (from serving meat to individual utensils).

Anecdotal is probably about as good as you're going to get since there was no official standardization, though.

The Oxford Symposium on food last year was about material culture. I don't know if they have any relevant papers.