As a prey animal the horse needed highly tuned senses, and a hair trigger for the flight response. However, jumping and fleeing at every sound expends a lot of energy. This is not very efficient, especially in times of drought, high temperatures or if food is scarce, when the horse needs to conserve its energy. To combat this the horses brain has developed the capacity to habituate to things, repeatedly occurring in the environment, that did not lead to fear or danger.
This allows the horse to become desensitized to things, and no longer react to them, if they do not result in perceived danger.
So the sound of a falling tree branch may initially cause the flight response (running away).
However if this sound does not result in the appearance of a predator, or any other danger, and is repeated several times, the horse will learn not to react to it.
The more often the event is repeated, the more quickly the horse becomes desensitized to it.
However if in the past the event has been linked to very high levels of fear, adrenaline, or flight response, then it can take much longer for the horse to habituate to it, and the flight reaction can reoccur suddenly again in the future.
Habituation, is what allows the horse to become accustomed to wearing a saddle and rider.
It is also what allows the horse to get used to human beings.
Unusual objects may at first cause the flight response, away from the object, however if the object is non threatening then the horse will eventually take no notice of it.
Habituation is a process, where the flight response is gradually diminished.
Trainers can use two main methods for desensitizing a horse to something.
These are: Approach and retreat, and Flooding.
Approach and retreat, involves the trainer approaching with the scary object, and retreating before the horse reacts to it. The approach gets gradually closer as the horse gets more confident that the scary thing will go away.
We almost want the horse to think that it is in control of the situation and that it can make the scary thing go away by keeping its feet still.
The important part of approach and retreat is to retreat BEFORE the horse reacts.
Progressively getting the horse used to more and more of the scary stimulus.
If the scary thing is too late to retreat and the horse reacts with the flight response
(running away) and the horse managed to get away from the stimulous, then the horse will become more reactive to the scary thing in the future, because it has learned that running away was profitable, i.e it worked!… it made the scary thing go away, or appear farther away.
Flooding involves applying or approaching with the scary stimulus and maintaining it at a level that causes a small flight response, until the horse stops reacting to it.
Then the object is removed, or retreats, to a safe distand
The horse is often desensitized to the saddle by flooding, because once the saddle is on, no amount of bucking or running will remove it, so the horse gives up and no longer reacts to it.
Scientists have discovered that horses and other animals can become habituated even to experiences that are painful.. Experiments have shown that if an animal is not able to rid itself of pain, it will give up trying and will become dull, listless and depressed. An example of this is a dressage horse that may have extreme pressure put on its mouth and sides, in an attempt to achieve collection, however these pressure are not removed the when the horse responds. At first the horse may “resist” or attempt to rid itself of the discomfort, by showing varying degrees of the flight response and may include, head tossing, bucking, rearing running away etc.
If the pressure is not relieved by any attempt to get rid of it, the horse cease reacting to it, and become dull, lethargic and depressed. This can even result in stress colic as the horse internalizes its distress.