Sometimes a person will not be able to talk unless they are using their hands. To prove this, while they're are talking- hold their hands down. They will shut up if they are inclined to 'hand talk'.
(Seems to be originated mainly from Italians, though not limited to them.)
Person 2: "Sorry, I can't help it.. I was hand-talking"
Person A: "Why must you talk with your hands? You know they can't see you thru the phone, right?
Person B: "I know, I just can't help but hand-talk."