First up in the Sense Series is vision. I chose this system to go first because humans are visual beings. As a result, we often make the mistake of assuming that our dogs are just as visually apt as we are. Now, since dogs are superheroes, they do have a few extra tricks of sight that we meager humans do not possess. However, we need to remember their limitations and keep them in mind when playing with and training our companions.
Before we even dive into the eyes of our dogs, one immediate difference from humans is placement. Dogs have evolved a more lateral location of their eyes, allowing for a greater panoramic view of their environments. While we can see about 180º and then the world fades behind our ears, dogs can see about 250-270º (depending on breed) around their head.
Our journey into the eye of the dog begins with the sclera and pupil. The sclera, or the whites of our eyes, often give away our gaze and allow others to read our intentions. Most breeds have very little sclera, making a dog’s gaze more difficult to follow. (They’re usually focusing their head around their nose or the best smells anyway, but we’ll get to that later.) In addition, our pupils can expand or contract with great range (1-9mm) depending on the light available in our surroundings and on our emotions or level of attention. Dogs’ pupils only range in size from about 3-4mm, making level of excitement difficult to gather from their eyes alone.
Night vision, one of dogs’ visual superpowers, is made possible by a “mirror” called a tapetum in their eye that reflects additional light back to the retina, creating a more visible image. This allows dogs to see better in the dark than we do, while also giving them demon eyes in our beloved Christmas card photos.
In addition to a tapetum, dogs have more rods in their retina than we do, further enhancing their night vision. However, as many of you may know, dogs are colorblind. Some people assume this means dogs can’t see color at all, but this is not the case. Humans possess three different cones responsible for our perception of red, blue, and green. Dogs, however, only have two, which fire in response to blue and greenish-yellow wavelengths. Therefore, dogs do not perceive the color red. This is most important to consider when choosing toys for your companion. A red ball on green grass makes no sense. It blends right in. Many toy companies market to the humans, not to the dogs. So, it is our responsibility to purchase with our animals in mind. The best color to get, especially when training, is blue, because they can more clearly tell the difference between the blue ball and the green grass.
Our version of a visual superpower is high definition, made possible by our fovea. The fovea is an area of our retina that’s packed with fully exposed photoreceptors. This enables us to perceive images directly in front of us with high levels of focus, detail, and color. Dogs don’t see the world as sharply because their photoreceptors are spread out more evenly across their retina. Therefore, they may not realize the ball you tossed is right in front of their paw, but they will be more likely to notice the flying bird out of the corner of their eye.
This leads into the last visual superpower of dogs. Have you ever wondered if your dog watches TV? Or how they manage to catch that frisbee while flipping backwards and upside-down? Dogs see the world with a higher flicker-fusion rate, meaning they see more of the world every second than we do. We see 60 images every second, which is what our (non-digital) TVs cater to. However, dogs’ eyes have a flicker-fusion rate closer to 70 or 80 cycles per second. Therefore, their TV experience is much like watching fluorescent lights flicker. It’s too slow for them to process a continuous image. I don’t know about you, but I’d trade my ability to watch TV for theirs to seemingly instantaneously catch a ball or delicious treat with their snouts any day.
Many of these superpowers and sacrifices evolved in order to be effective hunters and to survive in a world that moves quickly. Because they don’t see in such detail and don’t rely on vision as heavily as we do, they are able to take the world in via other senses that we just barely experience in comparison – similar to what happens when you’re blindfolded. This Sense Series will continue to explore these differences between us and our best friends.
In the meantime, think about how we can modify our training techniques and interactions to keep these visual limitations and abilities in mind. How do our behavioral expectations change based on what we know now?