How dogs see the world
How we interpret the world depends on the information we are able to gather from it. Our senses are how we gather that information. Different senses mean different perceptions.
Humans have vision as their stronger sense, while dogs have smell. We humans have the saying “Seeing is believing”, while for the dogs it might be “Smelling is believing”. Our memories are usually images; Dogs memories are sensory ideas. In humans, the visual system uses a greater portion of the brain, which means we interpret a situation mostly based on what we can see. Dogs instead interpret a situation mostly based on what they can smell out of it.
This does not mean that dogs have a terrible vision: Their vision is just different than ours. This sense also varies greatly among dog breeds: While sight hounds have a good vision, other hunting breeds that use their nose instead of their eyes have a poorer vision.
All dogs do have a better vision than humans in dim light, and this can be explained by their crepuscular nature which requires that they hunt at dusk and dawn. Their pupils are a lot larger which let in more light, and their larger cornea effectively gathers this light so that the brains have a clearer picture in mind. Dogs also have reflective “tapetum” behind the retina, which traps light and “recycles it” for a better chance of being use to discern images in the dark. This reaction is what makes dogs eyes eerily glow when they are caught in a flashlight beam. Interestingly, a lot of Nordic dogs lack this reflective “tapetum”, simply because they live in snowy regions where the snow surface does this light reflection work for them. It is therefore not an as important characteristic for these dogs survival, hence why the dogs carrying this genetic defect have successfully been able to reproduce.
Dogs large pupils have an unfortunate consequence: they result in a loss of depth of field, which results in a loss of focus and a blurred vision. Dogs are not so good at seeing details, and they need to resort to shapes to interpret the world around them.
Dogs are however great at seeing movements, as there are very sensitive to changes in their environment. If “it” moves, they will see “it”. That is why dogs sometimes cannot see a squirrel that is two feet next to them while they can see that same squirrel meters away if it is running. That is also why some preys have learned to protect themselves from predators by “freezing”.
Most dogs also have a larger field of vision than humans. While flat-faced breeds with eyes in from like Pekingeses do not have such a drastic larger field, dogs with long noses like greyhounds can see the world around them in an impressive field up to 270 degrees.
Finally, dogs do not need to see as much colors as tree-dwelling primates like the humans we are. They only have two kind of cones – one that is almost identical to humans’ blue cone and another one that responds so yellowish colors. For this reason, dogs cannot see reds, pinks and oranges. If you want your dog to see the ball you are throwing him, choose a yellow ball so he is able to discern it against the blue sky and against the green