Dogs have a reputation for their impeccable smell and hearing — not so much for their vision. But that stereotype is a bit short-sighted. For one, it’s a misconception that dogs see in black and white. Dogs can see colors, just not as many as humans can see. So what colors are visible to dogs — what does dog vision actually look like?
“All the evidence we have is consistent with dogs having color vision that is similar to people that are red-green colorblind,” says Mary Lassaline, veterinary ophthalmologist at the University of Pennsylvania School of Veterinary Medicine.
“The really critical thing when you're talking about color vision and dogs is the type of photoreceptor,” Lassaline says. Photoreceptors are cells in the retina that perform what’s known as phototransduction, or the process of converting photons of light into electrical energy. “And that’s what travels down the optic nerve through the visual pathway to the brain and results in vision.”
Two types of photoreceptors are called rods and cones. Rods are responsible for motion detection, “whereas cones are the exquisite color-detectors,” Lassaline says.
This is where dog and human eyeballs diverge in a big way. Humans, Lassaline says, have an area in the center of our retina “that is pretty much entirely cone,” so it’s concentrated for good color vision. However, dog retinas are rod-dominant. As a result, “dogs do a much better job than we do at detecting motion and seeing in dim light,” Lassaline says. Even though dogs have an area at the center of the retina for cones, it’s still mostly rods. Only about 3 percent of photoreceptors in dogs’ retinas are cones, according to a 2017 paper published in the Psychonomic Bulletin & Review, compared to 5 percent in humans.
Not only are humans more sensitive to color than dogs, but humans can also perceive more colors. Humans are trichromatic, which means we have three types of cones in our eyes. Dogs are dichromatic, so they only have two types. The two types of cones dogs have are capable of perceiving light on the yellow-blue-violet end of the light spectrum, but not reds or greens.
“Although the caveat is what I'm calling yellowish-green, blue-violet, we don't know if that's exactly how they perceive them,” Lassaline says. In other words, we don’t know if they see color the same way we do at a certain wavelength. What we do know is that their cones are sensitive to light at those corresponding wavelengths. She adds that dogs likely see red and green things as a sort of gray color.
She gave the example of a red flower with a green stem in a blue vase. A dog might see a gray flower with yellowish leaves and a blue-violet vase.
Since dogs also navigate the world through sound and smell, Lassaline says it’s of no great importance to cater to your dog’s color vision in daily life. “As best I know, none of my pet patients have been able to drive,” she jokes.
So there’s no need to worry whether your dog can accurately grasp the color of its favorite toy. Your pup can still have a perfectly joyful life without reds or greens.
