How dogs see things in a human world is probably as much a philosophical question as it is a physiological one. However, rather than bring Dr. Freud or Dr. Pavlov into the mix, let us stick to the physiological.
Researchers, disecting a dog’s eyeball, discovered that only approximately 10 percent of the photorecepters in a dog’s eye are cones; the majority of the photorecepters are rods. Human eyeballs, on the other hand, contain all cone type photorecepters. Rods are great for determining blacks and whites, but for colors, not so much. Cones are the crucial components required to recognize and distinguish the many colors in our world. That allows us to appreciate rainbows, The Simpsons and the charm of blue hair.
All colours are vivid and clear to us. Dogs, on the other hand, cannot distinguish between reds, greens, oranges and yellows, which is probably an excellent reason for not issuing drivers licenses to dogs. However, they can see whites, purples, light blues and varying shades of grey. Their ability to see different shades of grey is what gives them great vision in low light situations. A good thing to remember when entering a property at night that has watch dogs is that they will see you long before you see them.
Dogs can also see better with movement. For example, if your dog is in the garden at night and he sees you but you do not move, he may not recognize you and will bark. To reassure him, you need to move, then he will be able to recognize you. If you have a big dog, it behooves you to move as soon as possible.
Another interesting factor is that dogs have the ability to see at wider angles than humans. Whereas our peripheral vison is effective to about 180 degrees, a dog can see at around 240 to 250 degrees. That makes it extremely difficult to sneak up on a dog, even from behind.
Pet owners often claim that their dogs enjoy watching TV with them. Actually, the speed at which TV images appear on the TV screen is perfect for humans but not so perfect for dogs. The fact is, if your dog is watching TV, it is mostly for the sounds, not the images.
The way a dog sees TV images is completely different. To them, the images are moving at a much slower rate than they are for humans. To dogs, the images appear like old-timey movies appear to us, grainy and slow. If your dog enjoys dog movies, do not get too excited, it is actually the curious sounds emanating from the TV that stir his interest. It will be Lassie’s barks, not her heroics in saving Timmy, that will capture your dog’s interest.
Dogs are infintely more responsive to sounds and smells than visual stimulation. That is very apparent when they rely on their noses and ears to identify another dog or a human.
It is the wise pet owner who respects the extents and limitations of their dog’s abilities and lack thereof. Training your dog effectively can only be accomplished when you understand how your dog acts, thinks and functions. With knowledge and understanding, you can truly become your dog’s best friend.