It was once thought that dogs were totally colorblind and that they looked at the world in black, white and gray. A study that was published in 1995 in the Journal of the American Veterinary Association dispelled that myth.
The study revealed that dog retinas do possess color-sensitive cones that allow dogs to see some colors. They just don’t have as many cones as humans do. Thus, the colors that dogs see don’t look as rich and vibrant as the ones that humans see.
Scientists refer to the canine range of color vision as dichromatic vision because dogs have only two types of light-catching retinal cone cells, which contain pigments that perceive specific wavelengths of color, while humans have three types of cone cells in their eyes. Human vision is said to be trichromatic. Because of this, dogs do not see as many colors as we do. Dichromatic vision is similar to the vision of a red-green colorblind human.
While they do see black, white and shades of gray, their color vision is limited to yellows, blues and violets. Dogs cannot see red, orange or green. Red, orange and green appear as yellow or blue to dogs.
If one looks at a color wavelength graph for both human and canine vision, it is easy to see the difference between the two-legged and four-legged animals. The human graph starts with shades of red and continues on through shades of orange, yellow, green, blue and purple. The canine graph shows that dogs see the reds, oranges, yellows and some greens as yellow. Deeper shades of green appear gray on the dog graph. The blues and purples on the dog graph are not quite as vivid as they are on the human graph.
Another way of saying this is that dogs see the color blue, but deeply colored shades of violet appear to be blue. Blue green shades appear gray to dogs. Canine colorblindness does not allow the dog to see shades of red and green.
If you throw an orange ball or toy onto green grass, the dog will see it as yellow against yellow. This does not mean that the dog cannot see the ball. Dogs are able to find the ball because they track the movement. In fact, canines are better at detecting movement than human beings are.
Research does show that dogs can distinguish more shade of gray than human beings can. The reason for this is that dog retinas have a larger number of rod cells, which are responsible for perceiving shades of gray. The rod cells need less light than cone cells that perceive color to function.
Dogs actually have more rods in their eyes than humans do. This allows them to see better than us in low light conditions. However, rods do not pick up color and do not play a role in the colors that dogs are able to see.
Although dogs are colorblind, they do not appear to be handicapped by their inability to see all the shades of color that we humans do.
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