Is everything in a dog’s world black and white? That idea been widely accepted for decades, but new understanding of canine anatomy and behavior have shown that, while they can't see the same colors humans do, dogs are not color blind.
Technicolor may be beyond their comprehension, but research shows that the dog’s eye can see much more than shades of gray.
What Is Color Blindness?
English scientist John Dalton (1766–1844) conducted some of the first studies on congenital color blindness in the late 18th century. Dalton became aware of the phenomenon because both he and his brother could not recognize some colors, confusing scarlet with green and pink with blue.
In humans, this defect in red–green perception is common. It is caused by abnormalities in color-detecting molecules, known as cones, in the retina. The retina is a lining at the back of the eye that converts light into electrical impulses. These signals are then conveyed, through the optic nerve, to the brain, where an image is formed.
People missing some of these color-detecting molecules (also known as photoreceptors) won't recognize certain light wavelengths. Such people are called color blind, but they actually can make out some hues. Red-green color blind people can still discern yellow and blue, but items in red will appear gray or brown to them.
Myths About Color Blindness in Dogs
The notion that dogs see only in black and white has been attributed to Will Judy, a lifelong dog fancier, writer, and founder of National Dog Week. He claimed to be the first to declare that dogs had poor vision, able to see single shades and tones and only general outlines and shapes.
"It's is likely that all the external world appears to them as varying highlights of black and gray," Rudy wrote in his 1937 manual, Training the Dog.
In the 1960s, other researchers hypothesized that the only mammals that can discern color are primates. There was little research to back up this assertion, especially in dogs; nevertheless, it soon became common knowledge that our canine pals are color blind.
Are Dogs Color Blind or Spectrum Challenged?
In the last few decades, examinations of the canine eye structure have revealed some differences in basic design between humans and dogs. The differences were driven by function and evolutions.
Dogs developed their senses as nocturnal hunters, tracking and catching critters at night. Their eyes are adapted to see well in the dark and to catch movement. For the purpose of hunting in the dark, canine eyes have a larger lens and corneal surface and a reflective membrane, known as a tapetum, that enhances night vision.
The retina is where scientists have found the key to the difference in color perception between dogs and people. The retina is composed of millions of light-sensing cells. These include:
- Rods, extremely sensitive cells that catch movement and work in low light;
- Cones, work in bright light and control color perception, and,
- Photosensitive retinal ganglion cells, newly discovered cells that have no apparent impact on sight but appear to be involved with regulation of circadian rhythms.
It’s the composition of the cones that make the difference in color perception. Humans and a few other primate species are trichromatic, which means they have three kinds of cones. Dogs are dichromatic, having only two.
Each type of cone registers a different light wavelength. The one for red and green gives humans their appreciation for a red rose or a Granny Smith apple. Dogs, and some color-blind people, are missing red-green cones.
Dog Vision, a web site devoted to canine color perception, printed this side-by-side comparison of how the two species register the color spectrum.
So What Colors Can Dog See?
Scientists now believe that a dog’s color vision is similar to that of a person who has red–green colorblindness, according to research conducted by Jay Neitz, who runs the Neitz Color Vision Lab, in the department of Ophthalmology, University of Washington.
Dogs can make out yellow and blue, and combinations. This renders a lot of the world grayish-brown. That lush green lawn? It probably looks like a field of dead hay. That royal red velvet cushion? Still comfy, but it probably comes across as a dark brown blob to the dog.
Dog Vision also offers an online tool to help you see things as your dog sees them. There are also apps that you can use to see what your dog is seeing at any time.
To human eyes, this picture shows a redhead, a young Leonberger named Emily, pausing by bright red lilies in a lush green garden.
Left: As human eyes see this garden scene. Right: The same scene through canine eyes, as interpreted through the Dog Vision Image Processing Tool.
What Does This Mean to Your Dog?
Knowing that dogs don't see certain colors, it would make sense to choose products that may be less aesthetically pleasing to you, but will be an eyeful for your dog. This knowledge may help explain why some dogs go crazy over yellow tennis balls, but are apathetic about the same ball in pink or red.
Writing in Psychology Today, AKC Family Dog columnist Stanley Coren offered this observation: "One amusing or odd fact is that the most popular colors for dog toys today are red or safety orange (the bright orange red on traffic cones or safety vests). However red is difficult for dogs to see. It may appear as a very dark brownish gray or perhaps even a black. This means that that bright red dog toy that is so visible to you may often be difficult for your dog to see. That means that when your own pet version of Lassie runs right past the toy that you tossed she may not be stubborn or stupid. It may be your fault for choosing a toy with a color that is hard to discriminate from the green grass of your lawn."