It's well known that dogs are colorblind and generally have worse vision than humans do—a deficit they make up for with far superior senses of smell. But what does "worse" mean, anyway? What's it really like to see through the eyes of a canine?
BBC Earth has the answer, and it's shared through the lens of some truly adorable puppies. The video above does a nice job of visually representing what dog sight is like: they mostly see blue and yellow, due to having only two type of cone cells, but they process vision faster, which BBC Earth describes as essentially being able to see in slow motion. Combined with Wolfram Alpha's famed dog vision simulator, you should have a good idea of what it's like to see through your pup's eyes.
Cute puppies aside, BBC Earth's video broaches an interesting question: How do dogs' and humans' differing eyesight affect the way they interact with the world? Naturally, there are the broad differences: Dogs rely far more on their sense of smell, while sight and touch are key navigational tools for humans. But even if dogs can't see the color orange, research suggests they still use their eyes much like humans do.
Studies have shown that human infants are able to recognize faces early in their development, as young as three months in some cases. This is expected, as humans rely heavily on our refined sense of sight in everything we do. But what about dogs, who have comparably poor eyesight, spend the first two weeks of their lives with their eyes shut, and smell each others' butts to say hello? Do they grow up looking at faces too?
Research published in a 2011 paper in Animal Cognition tracked dogs' eye movements as they were shown a variety of photographs of dogs, humans, and inanimate objects, in a bid to understand dogs' cognitive abilities. The authors found that "dogs focused their attention of the informative regions of the images without any task-specific pre-training," and that the dogs paid most attention to other dogs, some to humans, and little to inanimate objects.
The authors note that it's not clear if the dogs' preference for photos of other dogs is reflective of their innate interest or their lack of understanding of what the other photos were. That aside, the research suggests that sight, and not just smell, is important to dogs' recognition of other dogs (and humans, to a lesser degree). So while sniffing each others' rear is a key part of a dog greeting, it appears that even if they can't see well by our standards, dogs do rely on visual cues in identifying each other.
In fact, dogs are pretty good at using visual cues from humans, too. Other research has shown that "domestic dogs are unusually skilled at reading human social and communicative behavior," which may be the result of the tight developmental relationship between humans and domesticated dogs. But curiously enough, the reliance on facial cues may ultimately be the result of sociality, not simply human influence. A 1970 report published in Behaviour showed that wolves, which have complex social structures, can recognize more facial expressions than can foxes, which don't have such developed social relationships.
To bring things back to BBC Earth's puppies, we tend to think that our development is shaped by how we're able to interact with the world. So if a puppy has worse eyes than a toddler, that puppy must not develop the same reliance on sight. While direct comparisons between the visual development of a puppy and a toddler is far from apples-to-apples, it's still interesting to note that sight is part of both of their cognitive developments, even if the two don't see the world the same way.