Habituation and sensitization

What is a learning process ?

A learning process is a durable change of an individual’s behaviour as a result of a past experience, expressed by the animal following exposure to environmental stimulus (or stimuli)*. The animal will reproduce this new behaviour when faced with the same stimulus. As a general rule animals will change their behaviour in the way which is most favorable to them.

Habituation and sensitization : non associative learning processes

Habituation and sensitization are termed « non associative » learning processes . This type of learning process is demonstrated either through a decrease or an increase of a behavioural response following the repetition of a stimulus.

What does habituation mean ?

Habituation is a process where the intensity of a response to a stimulus (examples : fly sprays, showering, going through water, loading in a trailer, noise of fighter planes overhead…) gradually decreases following repeated exposure to the stimulus (decrease or total disappearance of the initial behaviour observed when first subjected to the stimulation). In other words, it is making familiar or neutral something which was not to begin with (a new object, a new situation).
The horse gradually learns to react less and less, or even not at all, to a stimulus which is not associated to a consequence. He learns that a calm reaction is more appropriate, as it is more economical than alertness or flight.

Why should we accustom the horse to something ?

Habituation can be useful to :

• Make stressful handling situations easier and safer (transport, clipping, shoeing,  care, injections, administering de-wormers...)
• And to accustom the horse to new stimuli which could cause innate fear due to :
  • Size (large tractors or trucks...)
  • Intensity (gunshot, fighter planes overhead...)
  • Newness (a car which was not parked there yesterday,  a new obstacle…)
  • Or their suddeness (person arriving from a corner of the school without warning, arena watering system starting up …)

This type of learning can be applied to horses of any age, from foals, to young horses in training or for adult horses.

How should one proceed to accustom a horse to a stimulus ?

Inducing habituation should be done in steps, increasing the intensity of the stimulus very progressively without ever going above the tolerance thresholdlimit where the horse begins to be frightened. The intensity of the stimulus to reach this threshold will be different from one horse to another, and will evolve as habituation sets in. If however, we remain too far below the tolerance threshold, there is no learning. This is a fine limit, and sometimes difficult to apprehend. It means capturing the animal’s attention, without putting him under pressure. How should one go about it ?

Step 1 = identifying the tolerance threshold

The tolerance threshold is the moment when the horse starts to react when exposed to a stimulus. It is often when the first signs of fear appear.

Example:Let us take the example of attempting to determine the tolerance threshold with regard to applying a spray…
1) I am standing 2 meters away from the horse with the spray bottle in my hand. The horse is not particularly attentive, his neck is low and relaxed, ears are relaxed. → Everything is fine, I can go on to the next step.
2) I am now standing close to the horse, with the sray bottle in my hand. Now the horse starts to look at it, ears are pricked, his neck goes up slightly. → I have reached the tolerance threshold limit, this step requires consolidating, or going back to the previous step.
3) I touch the horse with the spray bottle. His ears are pricked, neck  arched, eyes are wide open and muscles are tense, he may even start to throw his weight back onto his quarters and start « snort ing». → This is above the tolerance threshold, I should go back to a previus step and reassure the horse.
4) I activate the spray and the horse either pulls back or flees.

→ Too late ! I went too far, the exercise is a failure.

Step 2 = planning the sessions and defining the number of stages.

Depending on the horse’s sensitivity and temperament, a certain number of stages need to be predetermined (distance between the horse and the object, intensity…), the first stage being the tolerance threshold. Subsequently, each stage needs to be confirmed before going on to the next stage, this means repeating it several times (2 or 3 attempts) without the horse reacting, otherwise you may need to go back down a stage. For the horse to be in the best possible conditions, the stimulus should be removed between each stage to allow the horse to relax. Whatever the case, do not hesitate to multiply the number of stages, with only a small difference between each, and  favor short sessions (of around a few minutes) and space out repetitions. Far from being a waste of time, this manner of proceeding is the key to success. It is the best way of avoiding going above the tolerance threshold and and having to start the whole process over again.

Example : Let us go back to the above example of the spray, when for example your horse lets you come up with the bottle in your hand, but demonstrates signs of fear if you try to activate it. 6 stages can then be defined :
•    Show the horse the object without activating it
•    Activate the spray gently at a distance from the horse (a few meters away)
•    At the same distance activate the spray with more intensity
•    Activate the spray near the horse but not towards him.
•    Activate the spray gently in the horse’s direction
•    Activate with more intensity in the horse’s direction

Step 3 : Start off in a quiet environment

To begin with, we will favor a quiet environment, in conditions where the horse remains as  receptive as possible.

Example : In the example of accustoming the horse to a spray, start off in a closed  grooming area, when there is no outside noise or agitation. (other horses going past, noise of the tractor, people in the stables…..)

Step 4 = generalizing to other environments

Once the lesson is learned in a calm environment, the process will be entirely repeated so as to confirm it in different environments. When the horse is no longer afraid wherever he is, he is said to have generalised. When a stimulus has become familiar in a given situation, the horse will demonstrate a weaker initial reaction if the stimulus is presented differently (similar stimulus, or same stimulus in a different place)

Example : My horse allows me to use a spray on his tail in the grooming box at the stables. Will he accept it in the yard with someone holding him ? or at a show when tied to the trailer ? ...

What if it doesn’t work ?

• Is your horse particularly emotive ?
• How long has he been frightened of this particular stimulus ? If it is a very old fear, it will be more difficult to accustom the horse using only the habituation technique.
• Was the proceedure respected, was it gradual enough ?
• Is it due to a lack of generalisation ?
• Was the process repeated enough ?
• Was the learning process too complex ? Request one simple thing at a time, otherwise the horse will have difficulty in understanding the request.
• Was the intensity with which the object presented too low? One should not go over the tolerance threshold, but remaining too far below it means the learning process is non existant.
• Did you go beyond the tolerance threshold ? Sensitizing the horse to something instead of accustoming him is not a good idea. Go back down a stage before taking it any further.
• Are there any associated stimuli which could increase fear ? Make sure you are working in a calm environment.

Unbeknown habituation

« My horse no longer reacts to the lunge whip when lungeing ». « I am keeping my leg on, but my horse is not going forward »….Even though habituation is generally a voluntary learning process, sometimes our actions have unwanted effects for the horse’s education and training : constantly using the lunge whip behind a horse on the lunge, moving or putting one’s legs on when riding… Without realising it, we are gradually teaching the horse to ignore some of our requests. This is known as « unbeknown habituation ».

Passive habituation

Another habituation process, consists in placing objects which the horse will encounter when he is being worked out, in his living environment (stable, paddock, field). He becomes gradually and passively accustomed to them. This is known as « passive habituation ». However , one should be careful not to create a stressful situation for the animal, and move the objects from place to place so as to generalise them. This means finding the balance between monotony, and excessive stimulation.

What does sensitization mean ?

If the horse’s tolerance threshold has been exceeded, repeating a stimulus can lead to a phenomenen which is the opposite of habituation : sensitization. The horse then learns to react  with intensity to the stimulus applied. Generally, the stimulus is unpleasant and sensitization occurs when the horse cannot avoid or flee exposure. The situation increases his initial fear. His attention level is higher, and his response to the stimulus faster and more intense.
Example : the horse pulls back violently just on seeing a bottle of spray following the fact that the spray was not correctly presented.

What processes lead to sensitizing a horse ?

Sensitization occurs when a stimulus is presented above the tolerance threshold. Each time the stimulus is presented, the horse’s reaction becomes more intense.

Sensitization is more often than not involuntary

Sensitization can occur involuntarily with a very delicate or sensitive horse, or when the habiuation process was not gradual enough. If we are not careful the horse will react more and more violently. Sensitization to sprays, injections, the smell of alcohol, the noise of clippers, the rider unfolding a map when out trekking… these can all lead to the horse panicking in a given situation. This is why it is vital to pay attention to the horse’s behaviour, and at the slightest sign of fear, attempt to understand where the fear comes from so as to avoid this type of reaction.

Voluntary sensitization : advantages and limits

Sometimes this learning process is used voluntarily to make a horse more reactive to a demand from his trainer, a request which he had become insensitive to. When the horse no longer reacts to the lunge whip, the trainer sometimes has to crack it to remind the horse to react. Subsequently, just lifting the whip, without shaking it, will get the horse going forward. Take care however, not to multiply situations of fear, which sooner or later could have consequences on the relationship between man and animal, and on the horse’s well-being .