You've always been told that dogs are colorblind, but what does that really mean? Dogs can actually see colors, but they have problem distinguishing red as we do. That leads to another question: how do we know this? We can't just ask a dog, because they will tell us whatever we want to hear. And it will sound like a bark. In this video, we learn about a famous dog named Retina who was the first to take a color vision test. Retina may have been the first, but two other dogs were tested before the research paper was published, because they needed to find out whether she was an outlier, or if most dogs have the same color deficiencies. See, dogs only have two color cones in their retinas, while humans have three, and the vision test shows us how that translates into actual perception of color. But you don't have to mourn for our dogs over their eyesight. They have other talents that make them feel sorry for us, like our inability to distinguish odors the way they do. -via Kottke