What science has learned about equine memory
Over the past two decades, and with increasing momentum in recent years, researchers have been piecing together a picture of equine memory that is far more sophisticated, nuanced, and frankly humbling than traditional horsemanship ever gave horses credit for. What these researchers have found doesn’t just satisfy academic curiosity, but has direct, practical implications for how we train, handle, and relate to our horses every single day.
The basics
Like humans, horses have multiple memory systems that operate differently and serve different purposes.
Long-term memory is where horses genuinely excel, and the research here is striking. In a landmark study, horses were tested on two instrumental tasks – one involving a reward, one involving avoidance of an unpleasant stimulus – and when retested 22 months later, they exhibited perfect recall performance in both tasks. This is not a species that forgets its lessons.
Earlier research by Dr Evelyn Hanggi at the Equine Research Foundation in California pushed this even further, with horses demonstrating long-term memory retention on discrimination tasks six to ten years after originally learning them. For context, that is a more impressive long-term retention record than has been demonstrated in chimpanzees in similar studies.
Short-term or working memory, on the other hand, is considerably more limited, and considerably more variable. Research has shown that horses can hold information in working memory for at least 20 seconds under calm conditions, but under stressful conditions, this duration drops to less than 12 seconds. That gap matters enormously in a training context, as we’ll come back to.
Procedural memory, the memory of how to do things, is deeply embedded in horses and forms the backbone of their trained responses. Once a behaviour is well established, it becomes largely automatic, which is why a well-schooled horse feels different to ride than a green one, and why poor training habits, once ingrained, are so difficult to undo.
The science of fear memory
Perhaps the most practically important finding in equine memory research concerns how horses store and retrieve fear-based memories, because this is where things get complicated for trainers.
Research in equine cognition suggests that emotional memories are processed and stored differently than other types of memories, with the amygdala, the brain’s emotional processing centre, playing a central role. This is the same structure that drives fear responses in humans, and it explains a phenomenon every experienced horse person has encountered: a horse that reacts violently to something it encountered just once, months or years ago.
What makes fear memories particularly persistent in horses is that they evolved as prey animals in which a single mistake, like failing to remember a predator’s location, or the sight of a threatening movement, could be fatal. The brain prioritised the retention of threatening experiences above almost everything else. The most fearful horses tend to be the most resistant to extinction, meaning that once a fear response is established, it is considerably harder to remove in horses that are naturally more reactive.
This has a direct implication for training: once a genuinely frightening experience has occurred, you cannot simply overwrite it. The memory doesn’t disappear; it gets suppressed or counter-conditioned, but it remains retrievable under the right circumstances. This is why a horse that seemed ‘cured’ of a loading problem can revert months later when something about the situation triggers the old memory. The original fear was never erased; it was simply quieter.
Horses remember you – specifically, how you made them feel
One of the most remarkable areas of recent research involves how horses remember individual humans, and it goes considerably deeper than simple recognition.
Research led by Professor Karen McComb of the University of Sussex and Dr Leanne Proops of the University of Portsmouth produced a result that genuinely surprised the scientific community. Horses were shown a photograph of either an angry or a happy human face and then, several hours later, met the actual person in a neutral emotional state. The horses’ behaviour when meeting the person in the flesh was clearly influenced by the expression they had seen in the photograph.
In other words, a horse that had briefly seen a photo of someone looking angry subsequently treated that person with more wariness when meeting them, even though the person was now behaving entirely neutrally, and even though the person themselves didn’t know which photograph the horse had seen. This form of emotional memory had previously been considered unique to humans.
Professor McComb summarised it simply: “Horses can not only read human facial expressions, but they can also remember a person’s previous emotional state when they meet them later that day, and, crucially, they adapt their behaviour accordingly. Essentially, horses have a memory for emotion.”
For horse owners, the implications are immediate and personal. The horse you’re riding today remembers how last Tuesday’s session ended. It remembers whether that vet visit was frightening or manageable. It has formed an assessment of you – your emotional reliability, your consistency, your tendency toward frustration – and it carries that assessment forward into every interaction.
Stress is the enemy of learning
Here is one of the most practically useful findings in the entire body of equine memory research, and one that has significant implications for how we structure training sessions.
In a study assigning horses to either ridden exercise, uncontrollable stress, or inactivity before a learning task, exercised horses achieved the learning criterion in the fewest number of trials. Stressed horses required significantly more trials to reach the criterion, performing no better than inactive horses.
The mechanism behind this is well understood. Prolonged high levels of stress hormones can affect neurons within the hippocampus – a brain region central to learning and memory. Long-term stress caused by housing or training conditions may therefore cause marked impairment of learning and memory abilities through the damaging actions of chronically elevated glucocorticoids on brain structure.
Put simply, a horse that is anxious, frightened, or chronically stressed is neurologically compromised as a learner. He is not being stubborn or slow. His brain is physiologically less capable of forming and retaining new memories in that moment. Pushing harder does not help; in fact, it is likely to make the situation worse.
Working memory performance in horses is also influenced by temperament: fearful horses showed better performance under calm conditions and considerably worse performance under stressful conditions than less reactive horses. This means that sensitive horses, often the most gifted and responsive when things go well, are also the most vulnerable to training environments that create pressure or anxiety. They require the most careful management of emotional state to learn effectively.
What this means
The science translates into some clear, practical principles that should shape how we approach training.
End on a good note, every time. As a sequential thinker, a horse will best remember the last event in a series. That is what the horse will recall, and establishing positive memories will help build a great long-term relationship. This is a memory architecture principle. The final emotional register of a session is disproportionately likely to be what your horse brings into the next one.
Consistency is non-negotiable. Because horses form lasting associations with specific people, environments, and routines, inconsistency is genuinely confusing to them at a cognitive level. A horse that receives different responses to the same behaviour from different handlers isn’t just getting mixed signals, he is being asked to hold contradictory memories simultaneously, which undermines the learning process.
Calm before you ask. Given what we know about the relationship between emotional state and working memory, a horse that arrives at a training session in an anxious or agitated state needs time to settle before meaningful learning can occur. Launching straight into demanding work with a tense horse is a waste of time at best, and counterproductive at worst.
Retraining takes time and patience for good reason. When you’re trying to replace a fear memory or an established habit with a new response, you’re working against deeply consolidated neural pathways. The burned-in nature of fear-based memories means that unwanted behaviours can resurface long after you think they’re gone for good, but you stand the best chance of success with patience and a positive approach. Desensitisation and counter-conditioning work, but they work gradually, and regression under pressure is normal, not failure.
Age doesn’t end learning. For those with older horses, recent research from the University of Pisa offers reassurance. Even elderly horses can learn new associations between stimuli and maintain their memory after ten days, though senior horses do show slower recall times compared to horses under 16 years of age. Ultimately, though, the capacity for learning doesn’t switch off; it simply requires a little more patience and repetition.
The bigger picture
What the research on equine memory ultimately tells us is that horses are not blank slates, reset between sessions. They are cumulative beings, carrying the weight, and the joy, of their entire history with them into every interaction. The horse that seems difficult, or spooky, or resistant, is often a horse whose memory is doing exactly what it evolved to do: drawing on past experience to predict what comes next.
When we understand that, something shifts. The question stops being ‘why won’t this horse do what I’m asking?’ and starts being ‘what has this horse learned to expect?’ That is a more honest question, and it leads to far better horsemanship.
References
- Lansade L, Guilbaud G, Neveux C. Characterization of long-term memory, resistance to extinction, and influence of temperament during two instrumental tasks in horses. Animal Cognition. 2013;16(6):1001–1011. doi: 10.1007/s10071-013-0639-2
- Hanggi EB, Ingersoll JF. Long-term memory for categories and concepts in horses (Equus caballus). Animal Cognition. 2009;12(3):451–462. doi: 10.1007/s10071-008-0205-9
- Proops L, Grounds K, Smith AV, McComb K. Animals remember previous facial expressions that specific humans have exhibited. Current Biology. 2018;28(9):1428–1432. doi: 10.1016/j.cub.2018.03.035
- Smith AV, Proops L, Grounds K, Wathan J, McComb K. Functionally relevant responses to human facial expressions of emotion in the domestic horse (Equus caballus). Biology Letters. 2016;12(2):20150907. doi: 10.1098/rsbl.2015.0907
- Valenchon M, Lévy F, Fortin M, Leterrier C, Lansade L. Stress and temperament affect working memory performance for disappearing food in horses, Equus caballus. Animal Behaviour. 2013;86(6):1233–1240. doi: 10.1016/j.anbehav.2013.09.023
- Hawson LA, McLean AN, McGreevy PD. The effect of stress and exercise on the learning performance of horses. Scientific Reports. 2022;12:1228. doi: 10.1038/s41598-021-03582-4
- Felici M, Curadi M, Baragli P. The Memory Abilities of the Elderly Horse. Animals. 2024;14(21):3073. doi: 10.3390/ani14213073