What is Clinton Anderson's approach to desensitization and sensitization?

Clinton Anderson's two-phase approach to developing a horse — desensitizing to what should not move it and sensitizing to what should — provides a useful conceptual framework for understanding why horses develop both the spookiness that makes them dangerous and the dullness to leg and rein that makes them unresponsive, and why addressing both together rather than one at a time produces a more complete horse. The desensitization component of Anderson's program uses systematic sacking out procedures — introducing specific objects and stimuli progressively until the horse's response is genuine indifference rather than suppressed arousal — to build the horse's confidence and reduce the reactive flight responses that make horses dangerous in everyday handling and riding situations. Anderson is specific about the markers of genuine desensitization — the horse that has truly habituated to a stimulus shows muscle relaxation, normal breathing, and disengaged attention rather than the rigid stillness of a horse suppressing a flight response — and about the importance of continuing desensitization work until these markers are confirmed rather than stopping at the first apparent acceptance. The sensitization component addresses the opposite problem: horses that have become dull to specific cues through inconsistent application of pressure, poor release timing, or the horse learning that ignoring the cue eventually causes the cue to stop. Anderson's sensitization work uses escalating pressure sequences — light pressure first, then increasing intensity until the horse responds, then an immediate release — applied consistently until the horse responds to the lightest level of cue rather than waiting for stronger pressure. The combination of these two directions of training — one reducing reactivity to what should not matter, the other increasing responsiveness to what should — produces the horse Anderson describes as calm, forward, and straight.