Science of Horse Training Demystified: Habituation and Sensitization

2 days ago
6 min read

If you had to pay attention to every stimulus in your environment, you would be completely overwhelmed with information. Luckily, our brains evolved to identify certain stimuli as unimportant and tune them out, allowing us to focus on what truly matters.

In fact, all living organisms use two converse processes that allow them to categorize stimuli as either inconsequential or important and respond accordingly. These processes are called habituation and sensitization.

Chalkboard with psychological definitions: habituation, sensitization, non-associative learning, trigger stacking, densitization, flooding, systemic desensitization.

Habituation and Sensitization

Habituation and sensitization are two forms of non-associative learning that, over time, will change an organism’s response to a stimulus after repeated exposure. They are both fundamental forms of learning that allow our horses to subconsciously filter and react accordingly to inconsequential stimuli. In this article, we will examine the two in-depth and uncover how they can either help or hinder our horse’s training.

Habituation

In the wild, survival depends on the ability to detect threats quickly enough to escape. Because it is easier to notice the one thing that is different instead of the hundreds of stimuli that are the same, the brain evolved to filter out the familiar. This makes novel stimuli easier to recognize.

Habituation is the process by which an organism’s response to an inconsequential stimulus decreases over time. Because the stimulus doesn’t mean anything, the animal stops responding to it after repeated or prolonged exposure.

Anyone who has ever lived on a busy road has experienced habituation firsthand. Likely, when you first moved in, the sounds of the traffic were annoying and possibly even prevented you from falling asleep. However, after some time, you probably stopped noticing the traffic, even though the sound had not changed.

Heavy traffic on a city street with cars and a red double-decker bus. Trees line the road. License plates and signs visible. — People who live next to busy roads become habituated to the sound of traffic

For our horses, habituation can occur with scary objects, like jump standards in the corner of the ring that never move, and the sound of the hay elevator in the barn, or sensations like the feeling of the saddle during a ride. Even though they may react strongly to these things at first, over time, they’re reaction diminishes until the stimulus is ignored.

Managing Habituation In Horse Training

We cannot avoid habituation when working with our horses and, therefore, as trainers, we need to harness this learning process for good and prevent it from hindering our training. For instance, habituation might be a good thing if your riding arena is situated by a road. At first, your horse might spook every time a car goes past, but eventually habituate to the sight and sound of passing vehicles. In that case, it is best that we just sit back, keep our training positive, and give habituation time to take place.

Chalkboard with tips to prevent habituation: avoid long exposure, vary environment, use positive reinforcement, and clear cues.

However, not all habituation is beneficial for horse trainers. Any stimulus that your horse is repeatedly exposed to will habituate. And while that can mean your horse will eventually drown out distracting stimuli, it also means they might start ignoring things you want them to focus on, like your cues and aids.

A horse that needs to be repeatedly squeezed to move forward or one that is ridden by a heavy-handed rider will likely habituate to leg and rein aids, respectively. This is why some riders feel the need to continually increase the pressure of their aids to get a reaction from their horse. Think of the beginner lesson horse that will only walk forward to the hardest of kicks. These horses have become habituated to gentler aids and no longer feel them.

Rider in a red shirt and brown pants on a white horse with a brown saddle in an outdoor arena, lined with bare trees. — When being ridden, the horse will habituate to the feeling of the saddle and bridle, and, if not used properly, our aids as well

Once habituation is understood, it is easy to keep our horses sharp to our aids:

Keep your aids meaningful and avoid repeated exposure if there is no reaction
The aid must be given precisely and released the moment your horse responds
If your horse needs to be kicked repeatedly or constantly slowed down with the reins, you may need to go back and reconfirm the basics.

Person in black jacket and cap trains a rearing tan horse indoors. Another person in red stands nearby, watching intently. — Increasingly fearful reactions to a stimulus are an indication that sensitization is occurring

Sensitization

The converse of habituation is sensitization. Sensitization occurs when, for one reason or another, a response increases in intensity with repeated exposure to an inconsequential stimulus. Where habituation eventually leads to little or no reaction, sensitization makes an organism react more intensely. For instance, your horse might have a bigger spook each time a car passes by.

Sensitization can explain why our horses act fearfully to seemingly minor stimuli, especially when paired with other arousing events. Your horse might be used to the cars passing on the road, but suddenly spooks when there are also gunshots coming from the woods. This is a form of sensitization called trigger stacking.

The reaction to a seemingly minor stimulus occurs as a result of the accumulation of multiple stressors over a short period of time. Individually, your horse may be able to deal with barking dogs, flapping flags, and noisy children playing by the arena, but when presented with them all at once, the horse spooks. The fear of each stimulus stacks until the horse is over threshold and has a strong reaction.

Equestrian in black helmet rides a brown horse, performing in an outdoor arena. Horse is spooking and trying to turn to the right — Trigger stacking can explain why a horse reacts fearfully to seemingly minor stimuli

We can manage sensitization in our horses’ training by keeping them in a calm, relaxed state of mind and avoiding stacking triggers. Your horse is unlikely to learn if they are in a state of heightened arousal; therefore, when training, you want to avoid sensitization.

Will My Horse Habituate or Sensitize?

Unfortunately, it can sometimes be hard to predict if habituation or sensitization will occur. Some horses might get used to certain stimuli while others have bigger reactions over time. Multiple factors contribute to a horse becoming sensitized to, rather than habituated to, a stimulus.

Chalkboard lists factors contributing to sensitization, including interval, tone, and speed.

The more intense, loud, high-pitched, and unpredictable something is, the more likely sensitization is to occur. Additionally, if your horse is in a heightened emotional state, anxious, or stressed at the time of exposure, or if they successfully perform an escape behavior (i.e., running to perceived safety and the stimulus stops), they are more likely to become sensitized.

Calm, relaxed mental states, predictability of interval and schedule, and low intensity sound and tone all foster habituation.

Desensitization

If your horse is spooky or overly reactive to something, desensitization can help them overcome their fear. Desensitization occurs when repeated exposure to a stimulus leads to decreased reactivity over time. Exposure therapy is a form of desensitization used to treat phobias in humans. It works by gradually exposing the subject to more intense stimuli (by bringing closer, adding more, making it move, etc.) as they learn to cope with it.

In horse training, the term desensitization is often misused to refer to a practice where the horse is exposed to a fearful stimulus in a way that causes a reaction. Once the horse stops reacting and relaxes, the stimulus is removed. By scientific definition, this is not desensitization but flooding.

Chalkboard comparing Flooding and Desensitization techniques. Flooding involves immediate exposure, while Desensitization is gradual.

Flooding involves forcing the subject to endure a fearful stimulus at full intensity until their fearful reaction subsides. However, this does not teach the horse not to fear the object, but instead to suppress their reaction to it, and can cause the horse to shut down if used excessively.

Chestnut horse with a dark halter, has a white training flag held up to their face — Flooding forces a horse to deal with fearful stimuli

In contrast, systematic desensitization involves gradually exposing an individual to a less intense version of the stimulus (such as a flag placed on the ground far away) and then slowly increasing the intensity (by bringing the flag closer, then slowly standing it up, and adding flapping). Care should be taken to ensure the horse remains relaxed throughout, and if they tense up, the stimulus should be reduced again. This increases the horse’s confidence and decreases their fear instead of teaching them to suppress their reaction to a stimulus.

Now you understand the two essential ways organisms learn to adapt to their environment: habituation and sensitization. You also know how to tailor your training session to help your horse ignore irrelevant stimuli while focusing on what matters and how to help them overcome fear. Next, you will learn about how organisms subconsciously form associations between relevant stimuli and reflexive behaviors in a process called classical conditioning.