Ask A Scientist
Why do dogs see in black and white?
Asked by: Katrina Wagner
School: Vestal Middle School
Teacher: Mrs. Jacqui Miller
Hobbies/Interests: Animals, dancing, music
Career Interest: Teacher or veterinarian
Answer from George Catalano
Professor of Mechanical Engineering, Director of t
Turbulence, fluid mechanics, aerodynamics, environmental ethics, modeling ecosystems
University of Virginia, Aerospace Engineering, 1977
All things Italian, creative arts, model trains and cars
Wife, Karen, is a registered yoga teacher at Yoga for Everybody at the Orthopedic Associates; lives with three Alaskan Malamutes, two more in our hearts
Dogs do see in color just as we do, but that is where the similarity ends. They can see only part of the range of colors in the visual spectrum of light. While humans have what is called trichromatic vision, meaning that we can see the entire spectrum, dogs are thought to have dichromatic vision and cannot see the range of colors from green to red. A dog's view of the world is cast in various shades of yellow and blue.
Humans also have the ability to focus on objects at greater distances than do our dog friends. A human can see clearly at 75 feet to the same detail a dog can see at 25 feet. We could then say a dog typically has 20/75 vision. Average eyesight for humans is 20/20.
Yet, let's not feel too superior to the dog! A dog can see in much dimmer light than we can. The central portion of a dog's retina is composed primarily of cells with rod shapes that work best in distinguishing shades of gray. We, on the other hand, have central regions in our retinas with cells of primarily cone shapes. These cones are great for colors but not very efficient in dimly lit situations. Dogs can also detect motion better than we can. They can also see flickering light better than we can. While we may be totally enthralled with the images we see on our new HDTV screen, a dog probably sees Seinfeld or American Idol as a series of moving frames rather than a continuous scene.
Perhaps a follow-up question might be the following: why do dogs see the way they do? I would suspect we would not have to look any furrther than to the ancestor of dogs, no matter the breed. The ancestor of all dogs, from Benji to Lassie to Rin Tin Tin to Marmaduke, is canis lupus, the wolf. Wolves are at their most active in the dimly lit environment at twilight and dusk. They need to detect incredibly small movements in order to survive, whether they are capturing prey or avoiding dangerous situations. The rods in the central core of the wolf's retina allow each wolf to exist and thus to fulfill an important role in the dynamic processes of nature.
The famous American author Mark Twain was very fond of dogs and was quoted as saying, "Man, rather than ascending from the lower animals, descended from the higher animals and there has never been a higher animal than the dog!" I suspect he might have been onto something. Let me see, what would I rather watch? The subtle and magical movements of plants and animals around a pond in rural upstate New York at sunrise or sunset, or the umpteenth repeat of a TV sitcom or game show? I'll leave that decision up to you!