Many people believe the myth that dogs see only in black and white. While dogs can see colors, they don't see them as people do. There are other differences between what a dog sees and what humans see. For example, dogs have better peripheral vision because their eyes are set farther apart. But that means their central vision, where both eyes are needed to focus on an object, isn't as good. Dogs typically have 20/75 vision.
What a Puppy Sees
A puppy's eyes don't open until eight to 14 days after birth. They start to see and have fully functional eyes between three and five weeks after birth. It takes infants longer to have fully functional eyesight. For the first three months, infants see only blurry shapes and have about 20/200 vision. It takes about three months for a baby to see faces and other objects.
How Dogs Perceive Colors
Dogs perceive colors differently from people. People have three cone cells, which allow color vision, whereas dogs have only two cone cells. Dogs don't see the full range of colors that people see. The biggest difference is that dogs don't see red and green. They mainly see shades of blue and yellow. People who are colorblind also have two cone cells, and what they see is similar to what a dog sees. Red-green colorblindness in people is more common than blue-yellow colorblindness.
Visual Advantage of Sight Hounds
Sight hounds are in the American Kennel Club's Hound Group. These dogs pursue prey by watching it. Sight hound breeds include the following:
- Afghan hound
- Italian greyhound
- Irish wolfhound
All dogs have more rods than humans do, which are light- and motion-sensitive cells. The increased rods help dogs see better in semi-darkness or twilight.
What Catches a Dog's Eye
There's a joke that began from the film "Up." When people are distracted easily, people say, "Squirrel!" The joke is funny because squirrels often catch a dog's eye, distracting the dog from what he was doing. But dogs aren't reacting to how they see the squirrel. Squirrels generally blend into the background, making them difficult to spot. Because of the rods in their eyes, dogs react to the sudden movement typical to squirrels. Dogs can detect this movement from half a mile away. Dogs can detect any small movement, not just squirrels. This makes dogs useful as hunters and guards.