A little roadster hackney pony I grew up riding had what my trainer called 'gear shifts'. She was INCREDIBLY attuned to verbal cues and was ridiculously sensitive to them. From a halt, one quiet click sent her into a prancy walk. Click too loud and she'd spring into a trot. One more click, faster. Another, even faster. Another, way fast. This 13hh pony could trot as fast as any canter because she was trained never to canter. Her "down shifts" were "easy" then "steady" to set the cruise control. If you said "whoa" you'd better hold on, cause she'd stop faster than you could blink.