[jumpinjeff]

Yep this is a total learned skill. It is almost a trick and then overtime with messing around with it (hint, reps) it gets easier and easier. And yes it starts by using the E string or the A or if you are more attuned to the higher notes the B string (my personal favorite because I see the fretboard easily through the use of the D shape and the B string is the root) I was not born with a great ear. I have been able to develop it through training. I say, based on my experience it is a learned skill.