The world is full of beauty, and so much of that beauty is due to color.
From the stunning blue of the sky to the lush greens of the trees to the shocking reds and purples of the wildflowers, color is critical to both our understanding and our appreciation of our surroundings.
But what about your dog?
Is the old idea that dogs see in black and white true? Are their worlds really that desaturated and colorless?
Or is it time for us to reconsider our preconceptions about canine color vision?
Science is shedding a whole new light on the way dogs see the world. Read on for some real eye-opening facts!
The Basics of Color Vision
How Does Vision Work?
Regardless of the type of animal, they’re attached to, eyes work in the same way.
Inside the eye, you’ll find various types of specialized photoreceptor cells — cells that translate light from the outside world into biological signals that the brain processes as images. The two major types of photoreceptors are rods and cones.
Both cones and rods are essential to both canine and human vision. But they serve very different functions.
What Are Rods?
Rods are highly sensitive cells, able to be activated by a single photon of light. Their sensitivity is what makes them so good at their job: detecting motion in even the lowest light situations and in even the furthest edges of peripheral vision.
Essentially, the more rods an animal has, the better it can see in the dark — and the better it’s able to sense and track moving objects.
But rods’ low-light acuity comes at a cost. With all of their energy devoted to motion detection, they’re not able to differentiate between colors very well, which is why everything looks monochromatic in very low light.
That’s where cones come in.
What Are Cones?
Cones require much more light than rods do to work, but when they do, the results are spectacular.
The world bursts into color — but the exact colors depend on the types of cones that are present.
Each type of cone contains special pigments, each of which detects a specific range of light wavelengths. Different wavelengths appear as different colors: blue light, for instance, is around 450 nm in length, while the yellow light is around 580 nm.
Cones are named based on the color of light they’re most sensitive to blue cones are best at detecting blue light, green cones are great at perceiving green, and so on.
But each type of cone can also detect a spectrum of shorter and longer wavelengths. Blue cones detect cyan and violet light in addition to blue, and green cones can detect orange, yellow and cyan light.
There’s also overlap between cone types, so multiple types of cones may activate in response to certain wavelengths. Both blue and green cones are activated by cyan light, allowing for even finer distinctions between tiny differences in hue.
The more cone cells an animal has, the more subtle variations in color it can discern. And the more types of cone cells an animal has, the greater the range of wavelengths it can perceive.
What Are the Different Varieties of Color Vision?
The type of color vision an animal has depends on the assortment of cones present.
Most humans have a trichromatic vision — that is, we have three different types of cones. The majority of our cones are red cones, followed by green, then blue.
Combined, these three types of cones allow us to see a whole rainbow of colors, from red to violet.
But up to 10% of humans, mostly males, have pigment deficiencies or abnormalities in one or more of their cone types. This results in colorblindness, the most common variety of which is red-green colorblindness.
Red-green colorblindness occurs when either the red or green cones work improperly (or not at all). Depending on the exact subtype, this can cause reds and greens to blend together, make reds or greens look gray or beige, or give yellows a reddish or greenish hue.
Some animals, including birds, goldfish, and foraging insects, have a tetrachromatic vision — four or more types of cones, often encompassing the ultraviolet or infrared wavelengths.
Birds, for instance, have five different types of cones, including a UV-sensitive cone.
This makes the world look incredibly different to them. One study showed that, of the many bird species that we perceive as identical between the sexes, 90% actually have distinct males and females when UV light is taken into account!
Monochromatic Vision and True Colorblindness
Many aquatic animals, including whales, dolphins, seals, and sharks, have just one type of cone, typically green. They can only perceive green, black, white and shades of gray — likely because green light travels so much better through water than other wavelengths.
And one animal, the skate fish, lacks cones completely. It sees the world in true grayscale, making it the only animal (that we know of) that is 100% colorblind.
That’s right — despite the myth we’ve all heard, total black-and-white vision is very rare in the animal kingdom, and you won’t find it in dogs!
Most other animals, including insects, fish, and non-primate mammals, have two types of cones, giving them dichromatic vision.
These cones don’t necessarily correspond to our red, blue, and green cones. Jumping spiders, for example, have green and ultraviolet cones, while many mammals have only blue and yellow cones.
Which brings us to our beloved dogs…
Dogs and Color Vision
What Types of Cones Do Dogs Have?
Dogs, like most mammals, have dichromatic vision. They have two types of cones: blue and yellow.
This means that they can see a blue and yellow light, as well as a few hues on the fringes of those wavelengths.
But red and green are indistinguishable to them, both likely appearing as a desaturated shade of gray, brown, or beige — similar to red-green colorblindness in humans.
Of course, very few things are pure red or green, so dogs can still distinguish between, say, yellow-green grass and forest-green pine trees.
But their vision is further complicated by the density of the cones they do have…
What About the Number of Cones in a Dog’s Eye?
Humans have a cone-to-rod ratio of about 1:9 — for every cone in our eyes, we have around 9 rods. This means that we’re very good at recognizing subtle differences between colors, but not very good at seeing in low light or noticing very slight movements.
But dogs have a cone-to-rod ratio of around 1:20. They have far more rods than we do, which is why they’re such good hunters and nighttime explorers, but we’ve got them outnumbered in the cone department.
So not only is your dog’s color vision limited to blue and yellow, even those two colors appear less vibrant to him than they do to you.
How Does a Dog’s Color Vision Affect His Life?
Your dog has never seen red or green, so he has no idea that they even exist. In that sense, he’s not suffering for his dichromatic vision — it’s how his species has evolved over millions of years, so it clearly works just fine for him!
However, evolution couldn’t account for the influence that our trichromatic selves have exerted on the canine world.
Take a look in your dog’s toy box and observe the distribution of colors inside it. How many toys are blue or yellow — and how many are red or green?
Chances are, you’ve got a pretty good rainbow going on in there. Yellow squeak toys, green tennis balls, red frisbees… it all probably looks quite fun to you!
But most of those colors look pretty murky and dull to your dog, blending together in a brownish-gray blur.
And when you toss that red frisbee out onto your green lawn? To your dog, it’s like trying to find a needle in a haystack — or a chocolate chip in a puddle of mud.
The difficulties your dog experiences with color can be more subtle, too. If his food bowl is red, for example, he may beg you for food even if he already has some, since the brown kibble blends in so well with the red bowl.
And if his designated dog blanket is green but your expensive humans-only blanket is beige, he could very easily get confused — and inadvertently end up in trouble.
How Can You Be More Considerate of Your Dog’s Limited Color Vision?
Want to see how your dog perceives your home, yard, or other surroundings? Snap a photo and plug it into András Péter’s Dog Vision tool, which lets you see an image through a dog’s eyes.
Then take note of what’s easy to see — and what isn’t. Things that are obvious to you may be nearly invisible to your dog, and changing them could improve both his quality of life and his behavior.
And don’t forget to think like a dog when you go to the pet store! Taking your dog’s inability to perceive red and green into account when selecting toys and supplies can make both of your lives easier in the long run.
Opting for blue or yellow toys will help him locate them easier and make it less likely that they’ll disappear in the yard or the lake.
Blue or yellow dog beds, blankets, bowls, and other accessories will attract your dog and reduce the likelihood of him messing with other objects around the house.
And if you’re trying to train your dog with dumbbells, agility poles, or other equipment, choose blue or yellow gear rather than other hues to hold his attention better.
None of this means that you need to limit your dog’s toys or other belongings to just these two colors. But if you opt for the whole rainbow, remember to be patient and understanding with him if he loses track of things.
Join 1,021+ Passionate Dog Lovers.
Can Dogs See Color? – How a Dog’s Vision Works (Video)
"If you think dogs can’t count, try putting three dog biscuits in your pocket and then give him only two."
-- Phil Pastoret