People love myths. The origins of myths are captivating, contentious, and contagious, and I quite frankly find them irresistible. Why would we even think dogs are color blind, and what does “color blind” really mean, and what in Sam Hill can we do about any of this? Well. I’m glad you asked.
Why?
In the 1930s, the publisher of Dog Week magazine, Will Judy, wrote to his readers that dogs had poor vision and were able to see single shades and tones and only general outlines and shapes. “All the external world appears to them as varying highlights of black and gray,” Judy wrote in his 1937 manual, “Training the Dog.”
Later, in the 1960s, graduate students hypothesized that the only mammals that can discern color are primates. There was little research to back up these assertions, but they were published anyway. Myth happens.
What does “color blind” mean?
There are three major types of color blindness. Red-green color blindness is the most common, and it’s the inability to tell the difference between red and green.
Blue-yellow color blindness is less-common, and it impacts your ability to discern blue and green, and yellow and red (or perceive purple and red, and yellow and pink).
Complete color blindness is called monochromacy, and is very rare. Depending on the type, you may also have trouble seeing clearly and you may be more sensitive to light.
When is this blog going to get interesting?
Right now! Here’s the deal: Dogs can see in color, but they don’t see “Roy G. Biv” like we do. They see more of a “Ygbb,” which may read like the sound they make when they sneeze, but it means: yellow, gray, brown, and blue.
Evolution is responsible for this, since dogs developed their senses as nocturnal hunters. Their eyes have adapted in such a way that they have a special light-reflecting layer behind their retinas 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,” explains AKC’s chief veterinary officer, Dr. Jerry Klein (in today’s featured image, you can see the reflective tapetum in the eyes of puppy Nitro).
The retina is composed of millions of light-sensing cells. Rods are extremely sensitive cells that catch movement and work in low light. Cones work in bright light and control color perception. Dogs have more rods than cones in their retina, whereas people have more cones.
A dog’s color vision is similar to that of a person who has red-green color blindness. In addition to color perception, dogs also have differences in brightness discrimination and visual acuity.
Since dogs can make out yellow and blue, and combinations of those colors, this renders much of their world grayish-brown. A lush green lawn looks like a field of shredded wheat. A bright red cushion is comfy, but to them it looks like a huge brownie (and this is why dogs eat cushions).
What in Sam Hill does it all mean?
I’m tempted to offer that we only purchase yellow or blue toys for our dogs, but we already know that doesn’t matter. In fact, the most popular colors for dog toys are red or orange. Clearly, those greedy dog toy manufacturers expect us to lose new and expensive gewgaws as soon as possible!
The bottom line is that dogs are supposed to be red-green colorblind and it doesn’t slow them down the least little bit.
Finally, and most important of all, I get to say, “There’s an App for that.” Apps such as Dog Vision HD by Laan Labs (iPhone) or Dog Vision by NGHS.fr (Android) are free, and allow you to see the world as your dog sees it.
Additional Notes
Humans and a few other primate species are trichromatic, which means they have three kinds of cones. Dogs are dichromatic, and have only two types. Each type of cone registers a different light wavelength. Dogs, and some color-blind people, are missing red-green cones.
There are some types of fish and birds that can see an even broader range of the color spectrum than people. These types of birds and fish are tetrachromatic because they have a fourth type of cone receptor to absorb ultraviolet light.
Dog Vision is a website by Andras Peter that offers an online tool to help you see things as your dog sees them. An online user can upload an image and then apply the modifications corresponding to any of the three perceptual differences of dogs (color, brightness, and sharpness). The effect of each perceptual difference can be applied separately or in any combination.
A leading researcher on the topic of vision in dogs is Jay Neitz, who runs the Neitz Color Vision Lab in the Department of Ophthalmology at the University of Washington.
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