Anyone who’s trained reining horses is aware that horses magnetize to gates, and avoid certain places in the arena. Trail riders are familiar with the problem of getting a horse to go straight, finally convincing him to quit pulling left, he immediately pulls right. Horses with problems seem to express their disagreement in resistance and we oppose this resistance until it seems to suddenly give up. There often isn’t a gradual development. It’s a “struggle, struggle, struggle,” then the horse flips the other way. This is called a knife edge phenomenon, and is common in many situations, not just horse training. Sometimes it is referred to as the tipping point. Picture yourself toiling up a slope, climbing, you finally reach the top, and there’s a sharp drop off. Now you’re sliding down the other side! Or It’s a little analogous to paddling a canoe into the wind. You fight to push it to the right to straighten it until the bow crosses the axis of the wind one millimeter, now you’re being blown to the right. Here you are riding a young colt alongside a fence. You ask for a turn into the fence with a leading rein. He resists, continuing on forward. You insist and persist, then suddenly he whirls into the fence and swaps directions, heading back the way he came. If you took advantage of the tipping point you would quit asking at exactly the moment he made the decision to turn on his own. Since horses learn from the release of pressure, you have taught him to turn with light signal. Or at least you’ve started the process. Assuming that “lightness” is your goal, using timing, rather than strength, or hanging on the reins, is your key!
I find that I have to watch carefully for the knife edge phenomenon when starting colts. If for example, I am trying to discourage a colt from his attraction to the gate, I put the rein, seat and leg corrections in before I get to the gate, when I know he’s going to pull toward it. I moderate my aids to use the least force possible, and when he passes the gate and gives up suddenly, I give up just as suddenly and allow my body to go back to neutral. If I were to keep “asking” for too long he would “over-correct”. Another use of the knife edge effect, particularly in the matter of “giving to the bit ” is softly, repeatedly “sponging” the reins, or “milking the cow” without increasing pressure, just repeating the squeeze about three times, then releasing, rather than pulling. Each squeeze is followed by a release, and the colt will finally “give” to the rein, at which point I relax my hand. It all starts again soon, but he gets the idea that he is responsible for being soft in the jaw and not resistant. In the end you want willingness.