We've all had it happen . . . You are riding along calmly and then your horse spooks at a mailbox you have passed a hundred times. I recently went on a horseback journey of over 1350 miles, riding the length of California, from the Mexican to the Oregon border. During the ride and since, many people said to me, "As much as they have seen, I bet by now nothing spooks your horses." I wish!
It's strange, but they seem to keep spooking at the same things, mailboxes and trashcans. Of course, in rural areas, some people seem to get a kick out of decorating and painting their mailboxes unusual colors and sometimes strange shapes. But that didn't seem to be the problem. My horses' reaction when spooked changed over time, as they developed trust, and they didn't do the usual "run first, investigate later" routine. In fact, they have pretty much learned to just freeze when frightened. But why do mailboxes and similar objects continually frighten them or cause a reaction?
I am not an equine ophthalmologist, but it is important to understand how a horse's eyes work and affect their behavior. Horse's eyes are located on the sides of the head, giving the horse maximum peripheral vision. With this peripheral vision, horses can see between 200-300 degrees around them. However, horses are theorized to have ramped retinas like trifocals, so they have to move their heads up and down in order to focus. Most of the time a horse is operating with blurry vision.
Horse's eyes are both monocular and binocular. Monocular means they can see out of each eye separately, sending different visual signals to the brain simultaneously. Binocular vision is seeing with both eyes at once, looking in front of them. Binocular vision is obscured or distracted when they are using mononuclear vision (looking out the side). It is with binocular vision that horses calculate distance. Since their binocular vision is best looking straight down their noses, horses often raise their heads quickly in order to focus on an object they get a glimpse of. This explains why your horse spins around suddenly to look directly at the object. You horse is actually trying to gauge just how far away this object is and the degree of danger. The direction your horses' ears are pointed will indicate where it is looking.
Trash cans and mailboxes seem to be common culprits of terror as they are caught in a horse's peripheral monocular vision. This means the horse comes upon the object visually from the side, out of focus and in one eye only. Therefore, the horse is unable to calculate depth perception or how far away this strange and dangerous object actually is. Remember when you have been riding towards something and it is not until you begin to pass it your horse reacts. The object is now being changed from being viewed from binocular to monocular and has no depth perception.
Once we understand what is happening with equine vision, spooking is more easily explained. Many mailboxes we approached were painted with loud colors and sometimes designed in strange objects. Although horses are thought to be fairly color blind, distinguishing only a few colors, it is probably more the unrecognizable shape and location of the object that creates a reaction.
Three other facts about horses' vision can help to explain their behavior. First, a horse's retina size actually magnifies objects to twice the size of human's eyes. Also, horses do not have as efficient recognizable recall of objects seen before, as do humans. And, the position of horses' eyes means they have some natural blind spots, immediately in front of the face, below the head and directly behind them. These facts alone can explain many of horses' reactions to strange objects.
Visual acuity is another concept that can help us better understand horses. This is the ability to separate objects at a distance. Three black lines on a white barn may be clear to us, but at a distance to a horse they tend to run together as gray and appear as one object. So at a distance many objects may appear as one huge object to your horse. Allowing time for your horse's eyes to focus and approaching slowly will help your horse to more clearly see the object.
Once you understand horse's vision differences and their primary instinct to flee at all potential dangers, you can begin to understand why it is silly to punish a horse for being frightened. Instead, learn to reward for the correct reaction to this fear. Riders often make the mistake of rubbing their horses and saying things like, Easy girl, or It's okay just after their horse reacts negatively to fear. Your horse may understand these actions as reward for reacting. Instead, reward them when they do not react negatively.
Another common mistake riders make is to anticipate their horses' reaction and telegraph this fear. Horses are prey animals and instinctually sense fear in the herd, so they can react quickly. A rider tensing up or breathing irregularly signals danger to their horse. Remaining relaxed and remembering to breathe when approaching obstacles that may be frightening for your horse will help you and your horse to successfully conquer new challenges.
I am not sure how humans learned this about horses' vision. Maybe Mr. Ed told them? I do know that understanding our horses' behavior and the functioning of their eyes can help us better know our horses and work toward building a better relationship with them.
For additional reading on Equine Vision see: