Despite its distinction as the largest ocular organ of any land mammal, and its superior acuity under certain conditions (such as darkness) to our own, the eye of a horse – how it works, sees the world, and perceives color and depth – is often underestimated. Why do certain objects erupt into high-headedness, circling, shying, or bolting?
Because a horse’s eye is the largest eye of any land mammal, the retina is larger, too. Images appear up to 50 percent bigger to them than to us, which can encourage their “flight” instinct to run first and ask questions later. To them, that Jack Russell approaching looks the size of a wolverine.
The equine eye is like a bifocal lens. The upper half is “far-sighted,” so, while grazing, it can scan the horizon for threats. The lower half is “near-sighted,” so for closer inspections, a horse raises its head to look downward, and bring an object into focus.
The Horse’s View
Compared to 20/20 human vision, horses are a slightly fuzzy 20/33, but see better than dogs (20/50) or cats (20/100). They also have superior night vision, thanks to a reflective panel in their retina that maximizes low light. Horses have both monocular and binocular vision. Each eye can transmit independent images and information to the brain (like two TV sets running simultaneously in the same room). They also have superb peripheral vision, except for “blind spots” directly behind, and up to approximately four feet in front of them.
Twenty-first century science is amending the misperception that horses are color blind. Photo-pigment research, published in 2001 by University of Wisconsin professors Carroll, Murphy, Neitz, and Ver Hoeve in the Journal of Vision, reveals that horses indeed see color, including pastel tones, albeit limited to the dichromatic (two-color) blue and green ends of the spectrum. Humans, in comparison, see trichromatically, (red, blue, green) as well as discerning shades in between (orange, pink, teal, etc.). Such shading on the equine color wheel is limited to yellow-tinted greens and slate-like blues, bridged by tones of gray.
The visual world of the dichromatic (like the horse) differentiates from the trichromatic in that there are no intermediate hues. When colors from the two ends of the spectrum mix, the result is either achromatic (white or gray) or de-saturates one of the hues to a pastel tone.
What horses see and how they see it can influence performance. 2008 Beijing Olympics show jumping course designer Steve Stephens has created some of the most memorable and challenging courses of the last two decades, including the optical illusion of ‘tunnels’ that stymied all but one entry – Chris Kappler and Seven Wonder – at the last fence of the 1995 American Invitational.
When Stephens first began designing fences in the 1970s, horses were assumed to be colorblind. “I didn’t necessarily put a lot of thought into color. You build your course, and its key elements, and then develop everything else around that. It’s the odd-looking fence that will call on the scope and bravery of a horse. Color is a tool, as is making a very narrow fence, or a funny-yet-delicate wall.”
How much a fence will test a horse depends on three criteria: color, weight, and looks. Stephens has painted fences in vibrant purples and violets, in peach and shrimp colors for tropical venues like Palm Beach, Florida, and in Adirondack greens and browns for Lake Placid, New York. Certain colors and patterns elicit different degrees of performance. The grand prix fence at Beijing known as the “Chopsticks,” had color, was extremely airy and delicate, and unexpected (after all, how many horses had seen a giant hand before?).
Stephens, like many designers, takes advantage of whites and pastels. “White combinations blend together. If I’m going to have a lot of white, or white and a pastel color, I’ll add a third color to help the rails stand out. We know certain pastel colors tend to cause horses to lose some depth perception and increase the possibility of faulting. It seems to happen most with yellow. Other colors, like pale pink or tangerine, cause a similar effect.”
Horses appear relatively uninfluenced by color when approaching a single, vertical fence, but the capacity to delineate between rails, or judge distances, diminishes when approaching a combination. “Triple combinations can be the most difficult, especially if they lack rails that incorporate a strong color, or accents like dark rings or bars.”
To understand horses, courses, and color is to understand how your equine partner sees the world. Fence color will not diminish the importance of walking a course beforehand, counting strides, or finding a safe, strong approach to your line, but it can provide a clearer picture of where faults might occur and how to avoid them.
If a better understanding of how your horse sees can pave the way to better performance, isn’t it time equine vision was seen for all it is worth?