How do scientists know that dogs are colorblind?

Answer 1

By examining the anatomy of the dog's eye and comparing it to human anatomy and that of other animals. They can tell a lot how an animal sees by how the eye is structured.

And they are not colorblind. they do see colors, just not as wide a spectrum as humans

http://www.uwsp.edu/psych/dog/LA/davis2.htm

Answer 2

There are two ways to work toward answering the question "What range of colors can dogs perceive?" One of these is anatomical, as Bozema stated. In the dog's retina, there are two types of cones, as compared to three in the human (and other primates) retina. However, the dog does not have the fovea found in primates' retinas. This is a small area of high concentration of only cones, and is capable of high acuity, that is, the ability to resolve very fine details.

The other approach is behavioral. One way would be to train the dog to respond by pressing a lever with its paw when two colored targets are different colors. Then by presenting pairs of different colors, you could begin to tell which colors the dog can perceive. For example, if you presented a gray square and a blue square, and the dog pressed the lever, that would indicate that he could tell them apart. If you presented a red square and a gray square and it didn't press the lever, that would indicate that it couldn't distinguish the red from the gray. The actual experiment would be more complex than this, but maybe this will give you an idea. There are other experiments along these general lines that could be designed.

Based on both the anatomy and the behavioral studies, researchers have concluded that dogs have color vision, but it is limited compared to humans, sort of like a human with red-green color blindness. Their results indicate that dogs perceive colors mainly in the blue to yellow range of hues, and that reds appear as grays or blacks. So compared to humans, they are color blind, however, that does not mean that they only experience things in shades of black, white and grays. In their own terms, their "colorblindness" is perfectly normal vision for them.

Since they lack a fovea, they can't distinguish the fine details humans can. It has been estimated that their vision is roughly 20/75 in human terms. However, they are much more sensitive to movement, and can detect extremely small movements. They also can distinguish their owners from strange humans based only on the way they move, not by recognizing facial features or anything we might use to tell one person from another. Because they have a higher proportion of rods, their vision under very low light conditions is better than ours. So ours is better in some ways, and worse in others.

Edit: Madison makes a good point. Applying a human definition of colorblindess to dogs is not appropriate. I think anytime you talk about dog's behavior, motivations, emotions, etc., you have to try to step outside a human frame of reference and into the dog's. It's not easy to do, but failing to try is a major source of the conflicts between humans and canines, IMO.

Answer 3

Dogs are considered colorblind because any vision disorder that involves color is considered colorblindess; however, they actually do see color. So they are technically considered colorblind but they do actually see color (the rules and catagories need to change so they are not considered colorblind since they see color).
They see colors, but in different shades and hues than humans do.

Answer 4

To be more specific, they examine the nature of the cells in the retina at the back of the eyeball, and compare them to those at the back of human eyes. Dogs' eyes do not have the same number or types of cone cells (the ones that detect color) as human eyes do.

Answer 5

they aren't. My friend has a red car, and my dog watches out the window all the time, and is only excited when he sees a red car...