When you look at a rainbow in the sky, you see shades of red, orange, yellow, green, blue, indigo, and violet. Can your canine friend distinguish the same range of color that you do? Does he see bands of black and white? Do the colors look blurred?
How dogs see color is a long-standing topic of research and the results are pretty amazing. While dogs cannot appreciate all the colors that humans do, their world is not entirely black and white. In fact, dogs live in a pretty colorful world.
What makes a color so “colorful?"
Color is discerned by the nerve cells in the eye. The retina of the eye has two main types of cells—rods, which detect light levels and motion, and cones, which differentiate colors. Human eyes have three types of cones that can identify combinations of red, blue, and green. Dogs possess only two types of cones and can only discern blue and yellow - this limited color perception is called dichromatic vision.
Humans may have more cones, allowing us to see more colors and see them brighter than dogs do, but dogs have more rods, giving them the edge when it comes to seeing in low light or identifying moving objects.
What is color blindness?
Color blindness is the term used for changes in the ability to perceive color. In humans, the degree of color blindness depends on which color receptors in the eye are affected. There are two basic types of color blindness in people: red-green color blindness and blue-yellow color blindness. A person with red-green color blindness cannot distinguish between these two colors. That makes Christmas pretty boring! Likewise, a person with blue-yellow color blindness can’t tell the difference between a yellow shirt and a blue one.
When it comes to distinguishing color, a dog’s normal vision is most like a person who has red-green color blindness. Having said that, no further degrees of color blindness have been recorded in dogs.
How does a dog’s vision compare to human vision?
Just because dogs don’t appreciate the entire spectrum of color that humans do, that does not mean they are unable to perceive different colors. They just may not see the “true” color of an object.
For example, the color red appears dark brownish-gray or black to a dog. And yellow, orange, and green all look a bit yellowish to a dog. Our furry friends see blue really well, but purple looks the same as blue to them. When playing a game of fetch, dogs cannot tell the difference between a red ball and a yellow ball. Luckily, they have a great sense of smell so they can usually identify their ball and avoid mix-ups when playing a game of fetch in the park.
“In addition to color perception, canines and humans have other visual differences.”
In addition to color perception, canines and humans have other visual differences. In some respects, canine vision is not as acute as human vision. Dogs are more near-sighted than we are. When looking at an object from the same distance, the object may appear crisp to us, but blurred to our dogs. Our canine companions are also less sensitive to changes in brightness. Basically, dogs simply do not have the ability to perceive color in the rich, vibrant tones that we do.
What are other visual differences between dogs and people?
Canines have some visual advantages over humans. Dogs have eyes that are set more on the sides of the head which allows them a broader range of peripheral vision than we have. The trade off is a smaller range of visual acuity so dogs do not have the depth perception that we do.
Dogs have pupils that dilate maximally, allowing them to capture as much light as possible. They also have reflective cells under the retina, which form the tapetum. The tapetum gives dogs the “shiny eye” appearance and also improves their ability to see in dim light.
Dogs also have more rod cells in the retina than their human friends. Rods are responsible for detecting light and motion, even small movements at great distances. So, when compared to humans, dogs see better in dim light (dusk and dawn) and can more accurately detect motion.
Why do dogs see what they see?
Nature equips dogs with special visual accommodations that allow them to survive and thrive in the wild. Seeing well in dim light and picking up slight movements in the forest at great distances improve the dog’s hunting ability. These assets also help a dog know when HE is the prey and needs to flee.
Times have changed and most dogs are members of our human families now, so we provide them with nutritious food and protect them from predators. Even so, these visual abilities remain in the canine family.
Most people know that dogs don’t see as well as humans, but there are a lot of misconceptions floating around about the way they see the world. But now a small web app, first uncovered by The Next Web, can show you how the world looks through your pooch’s eyes.
Dogs, contrary to popular belief, do not see the world in black-and-white. Their vision is actually most similar to people with red-green colour blindness. But there are other ways humans differ from dogs as well, including less sensitivity to both brightness and variations in shades of grey.
Dog Vision tries to take these factors into account. Simply upload a photo and in a few moments the app will show you how your dog would see that scene. Here are a few ways the photo will change.
Colours: Humans (and dogs) have two types of colour receptors: rods and cones. Rods handle peripheral and night vision - brightness and shades of grey. Cones deal with day vision and colour perception. Each of the cones detects a different wavelength of light, and through using our three types of cones, humans can detect a full spectrum of hues (in a similar way to how you mix primary colours in paint). Dogs only have two types of cones (like red-green colourblind humans), and this makes their colour vision very limited.
A vibrant Mardi Gras scene, as humans see it, changes from this:
To this when viewed by a dog:
Near-sightedness: Dogs are also very nearsighted compared to humans. A special test, custom-made for dogs, puts them at around 20/75 vision, according to Psychology Today. This means a human could barely see at 23 metres (75 feet) is what a dog can just about make out at 6 metres (20 feet). That’s why this scene of matadors turns from this in a human’s eyes:
Into this in a dog’s eyes:
Brightness discrimination: Dogs are substantially worse than humans at determining difference in brightness, or looked at another way, different shades of objects. In fact, dogs are twice two times worse at differentiating between shades than humans are. That’s why this photo of fall foliage changes from this:
Into this when a dog sees it:
But if you start to get sad for the pups, just remember your dog has an incredible sense of smell that basically lets it 'see' the world in different scents.
This article was originally published by Business Insider.
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Dog vision is very different from human vision. Dogs see the world in fewer hues than we do, but this doesn't mean our canine companions are completely colorblind. But even if dogs' visual worlds are not as clear or as colorful as ours, their ability to see motion is superior.
The human eye works thanks to three kinds of color-detecting cells called cones. By comparing the way each of these cones is stimulated by incoming visible light, our brains distinguish red wavelengths from green wavelengths and blue wavelengths from yellow wavelengths. Dogs' eyes, like those of most other mammals, contain just two kinds of cones. These enable their brains to distinguish blue from yellow, but not red from green.
Dogs are not completely colorblind, but their eyes are structured in a similar way to those of people with red-green color blindness, whose eyes also lack the third kind of cone normally present in humans, Jay Neitz, a color vision scientist at the University of Washington who conducted many of the modern experiments on color perception in dogs, told Live Science.
We can get an idea of what dogs see, Neitz said, if we assume their brains interpret signals from their cone cells much like the brains of people with colorblindness do.
Related: Red-green and blue-yellow: The stunning colors you can't see
To see blue and yellow, dogs and humans rely on neurons inside a part of the eye called the retina. These neurons are excited in response to yellow light detected in the cone cells (which are also inside the retina), but the neurons' activity gets suppressed when blue light hits the cones. A dog's brain interprets the excitation or suppression of these neurons as the sensation of yellow or blue, respectively. However, in dogs and in people who are colorblind, both red light and green light have a neutral effect on the neurons. With no signal to interpret these colors, the dogs' brains don't perceive any color. Where you see red or green, they see shades of gray.
"A human would be missing the sensations of red and green," Neitz said. "But whether or not the dog's sensations are missing red and green, or if their brains assign colors differently, is unclear."
Furthermore, like people with colorblindness, dogs may use other cues to distinguish the color we call "red" from the color we call "green."
Related: See 15 crazy animal eyes
"A lot of the time, there are good cues to help them figure it out; for example, red objects tend to be darker than green objects," Neitz said. "So, if it's a dark apple, a red-green colorblind person would know that it's probably a red one, and if it's a lighter apple, it may be a Granny Smith."
There is some evidence that dogs may be able to see colors humans cannot. A 2014 study published in the journal Proceedings of the Royal Society B (opens in new tab) found that the lenses in the eyes of a dog transmit significant amounts of ultraviolet light, whereas these wavelengths are blocked by human lenses. This suggests that dogs might see more blue light than we do.
How sharp is dog vision?
In addition to missing some of the hues perceived by human eyes, dog vision lacks some of the sharpness of human vision. In a 2017 study (opens in new tab), published in the journal PLOS One and conducted at Linköping University in Sweden, researchers designed a canine visual acuity test similar to the tests ophthalmologists give to people. Instead of having to discern letters of decreasing size, the dogs were rewarded with treats for correctly identifying images containing vertical or horizontal lines with ever-decreasing amounts of space between them.
The researchers discovered that dogs — or at least the whippets, pugs and the single Shetland sheepdog that participated in the experiments — were very nearsighted. The results of the experiment suggest that dogs, in well-lit conditions, have roughly 20/50 vision. This means that they have to be 20 feet (6 meters) away from something to see it as well as a human who is 50 feet (15 m) away from that same object.
Do dogs have night vision?
While dogs' night vision is fairly blurry, at roughly 20/250, according to the 2017 study, it is also much more sensitive than humans' night vision. Dogs are crepuscular, meaning they tend to be most active at dawn and twilight, according to the American Kennel Club (opens in new tab). While human eyes are chock-full of cones, which help detect colors and work best in bright daylight, dogs' eyes contain more of the light-detecting cells known as rods, which distinguish between dark and light and thus are at their best in low-light conditions, according to the Merck Veterinary Manual (opens in new tab).
Related: See the world from a cat's eyes
Many dog breeds (though not some of the toy dog breeds) also have a special eye layer, known as the tapetum lucidum, that bounces light back toward their retinas, essentially magnifying the light that does reach the rods there, according to a 2014 study in The Journal of Veterinary Medical Science (opens in new tab). The tapetum lucidum is what causes dogs' eyes to glow a bluish green when light shines on them at night, according to the Merck Veterinary Manual.
The takeaway? Dogs have better night vision than humans do.
Canine motion detection
While you might think dogs live in a dull, blurry visual world compared with ours, there is one area where their vision beats ours: They are much better at detecting motion. This is due to something called the critical flicker fusion (opens in new tab) rate. Imagine a light that flickers faster and faster. By the time the light is flickering 60 times per second, humans will believe the light is shining steadily. According to a 1989 study published in the journal Physiology and Behavior, (opens in new tab) that same light has to flicker roughly 75 times per second to fool a dog.
This ability likely enables dogs to spot moving objects, such as prey, much more quickly and accurately than humans can.
Additional resources
- Find out what your dog sees when it watches television, in this video from SciShow (opens in new tab).
- See what uploaded images might look like to dogs, on this website (opens in new tab) created by neuroscientist and computer scientist András Péter.
- Take a deep dive into the visual world of dogs in the book "Inside of a Dog: What Dogs See, Smell, and Know" (opens in new tab) (Scribner, 2010), by Alexandra Horowitz.
Bibliography
Byosiere, S. E., Chouinard, P. A., Howell, T. J., & Bennett, P. C. (2017). What do dogs (Canis familiaris) see? A review of vision in dogs and implications for cognition Research. Psychonomic Bulletin & Review, 25(5), 1798–1813. (opens in new tab)
Coile, D. C., Pollitz, C. H., & Smith, J. C. (1989). Behavioral determination of critical flicker fusion in dogs” Physiology & Behavior, 45(6) 1087–1092 (opens in new tab).
Douglas, R. H. & G. Jeffery. (2014). The spectral transmission of ocular media suggests ultraviolet sensitivity is widespread among mammals. Proceedings of the Royal Society B: Biological Sciences, 281, (1780) (opens in new tab).
Hirskyj-Douglas, I. (2016, September 8). Here's what dogs see when they watch television. The Conversation. (opens in new tab)
Miller, P. E., & C. J. Murphy. Vision in dogs. (1995). Journal of the American Veterinary Medical Association, 207(12), 1623–1634. (opens in new tab)