i beleive that after a ceratiain amount a experience/time in dogs (an that will be diffrent for diffrent folk, some are naturals, some never figure shit oot) that you can tell if a dog is trying, it should be even more apparent if you have brought dog on from a pup, but after seeing a dog work a few times, i can generally tell if it wants to run or not when its time to be slipped....
i must add, that if/when a dog a mine jacks, its not geed its p45 there an then, 1st ill ask me self some serious questions....
tho to be fair if i dont know them answers before i work the dog, i shouldnae be