Thank you Shannon. I will play with that. If I stop while walking at liberty or a lead line, he stops immediately but on a circle I have not found a good stopping cue. It might be just that he is further away from me as he does like being right next to me. Perhaps I can exaggerate that last step a little more. Will let you know. I have taken today and tomorrow off from horses, I needed a break!
Often the horse has given us clues (as Josepha has said so often, listen to the horse) about a behavior we'd like to get from them.
Two years ago I started working a very flighty Morgan gelding and since I had no enclosure worked on a lunge line. One of the things I wanted from him was an instant stop "when things go wrong," as with him had so often happened, throwing riders pretty badly, or bolting and running.
During the first part of his training when I was charging the clicker it was quite obvious he got it and would stop whatever he was doing, including even trotting away from me, if he heard the sound of the clicker.
Since I did not want this energetic (but good humored boy) to start mugging or charging for treats I went immediately to him when I clicked. He got to stand still for his treat. Worked fine.
You probably can figure out where this is going.
Soon he was playing "statue," with me. I cued by throwing the lead line down, or even the stick and line, or a piece of rope I might be carrying, anything. Anything hitting the ground meant to stop and wait for his treat.
Paid off big time when the old saddle I was using for training blew out the offside cinch billet and it peeled off over his rump. He literally slide to a stop, and stood facing foward on the circle expectantly waiting (even though he was a bit excited) for his treat.
The ideal is to remove the click eventually and have the cue itself be the bridging signal. If I say whoa, I say whoa slow. People that watch me can't figure out how a rider or handler saying whoa slow gets sliding stops from a horse, but that's the way it works.
If the horse is turning toward you for his treat when he halts on the circle, go too him immediately so he gets the idea that he doesn't have to move his feet at all. Just stand and wait. It's a good habit to give treats, at first, immediately for this very reason. Later you can begin, especially when treating a well established behavior, to stretch the time out, and should.
You can also reposition him on the circle just before actually giving him the treat reward. Whatever that might be. Praise, food, or scritches.