For decades, scientists thought that dogs view the world in plain black and white. However, relatively recent research into canine anatomy and behavior shows that man’s best friend actually sees things in color, albeit not as well as humans.
The notion that dogs have poor vision and can only see in shades of gray can be attributed to Will Judy, the former publisher of Dog Week magazine in the 1930s.
“It’s likely that all the external world appears to them as varying highlights of black and gray,” Judy wrote in a highly popular 1937 manual called “Training the Dog.”
This myth surprisingly persisted for decades until research in the 1960s examining the structure of the canine eye shed more light on the matter.
The human eye perceives color when certain wavelengths of light are reflected off objects and into the lens. The refracted light is then focused on the retina where photoreceptors called cones and rods interpret the message in order to be processed by the visual cortex in the brain. There are millions of these photoreceptors throughout the human retina.
Rods are responsible for our ability to see in low light levels, or scotopic vision, allowing us to perceive shapes and motion even in dim light or almost no light at all. Cones are made up of three different types of receptors (short, medium, and long-wavelength cones) that allow us to perceive color.
The most important difference between the cone and the rod is that the cone is more light-sensitive than the rod and requires much more light to enter it in order to send signals to the brain. This explains why we can’t see colors in the dark.
Initially, it was thought that dogs lack cones, which led to the conclusion that they can’t see color. Anatomical dissections, however, showed that dogs also have cones, but much fewer compared to humans. Additionally, humans and other primates are trichromatic, meaning they have three kinds of cones, whereas dogs are dichromatic, only having two types of cones. Dogs are missing red-green cones, so they can’t see these colors.
On the upside, dogs have more rods than humans, allowing them to see much better in the dark than us. Dogs are essentially domesticated wolves, nocturnal predators that need to have good eyesight in the dark to track and catch prey. The canine eye also has a larger lens and corneal surface, as well as a reflective membrane behind the retina, called the tapetum lucidum, which further enhances night vision. The tapetum reflects back the light that has already entered the eye, giving the dog’s eyes a boost. This is the reason why your pet’s eyes may sometimes appear to glow at night.
Although dogs aren’t as good as humans in the vision department, they more than make up for it with their noses and ears. Canines’ hearing is keener than ours and their sense of smell is about 1,000 times more sensitive than the human nose.
How dogs see colors
All of this is to say that dogs aren’t fully color blind. In fact, in many ways, dogs probably perceive color similarly to humans with various forms of red-green color blindness. Certain colors aren’t vivid and different hues of the same color are difficult to differentiate between.
That’s because for the two types of cones dogs have, one is for blue while the other absorbs wavelengths between a human’s version of red and green.
But how exactly do dogs see color? That’s impossible to tell without swapping eyes with them, but judging from their anatomy it’s likely they see best in shades of yellow, blue, and green. When these colors are combined, a dog’s brain will likely process these wavelengths in dark and light yellow, grayish yellows and browns, and dark blue and light blue. This may explain why dogs go nuts over chasing yellow tennis balls. They probably can see the tennis ball light up, especially against a green grass background which, to them, comes across as rather dull.
The people at Dog Vision took this information about the canine eye and used image processing to offer a momentary glimpse into how dogs see the world. The blurry images below are not a perfect reflection of how a dog truly perceives shapes and colors, but they do a good job at illustrating how different their eyes are from ours.
The reason why these images are blurry is that dogs tend to be nearsighted. A poodle, for example, is estimated to have 20/75 vision. However, dogs are much more sensitive to motion at a distance — anywhere from 10 to 20 times more sensitive than humans.
If you’d like to learn more about how these images are processed, you can read András Péter’s technical explanation, who programmed the app. You may also use the tool to upload images and create your very own dog vision pics.