Dogs have dichromatic vision, seeing the world through shades of blue and yellow with some gray. In humans, this is similar to red-green colorblindness. Beyond that, we know that dogs have weaker vision than ours, at least under some circumstances. Canine vision is adapted for a different ecological niche–while we have superior color vision and are better able to make out details, dogs have better motion detection, have a wider field of view, and see better in low-light conditions, all harkening back to their original role as predators. Squirrels beware!
Through the Eyes of Your Dog
Our understanding of how canine vision compares to ours largely comes through studying the rods and cones in their eyes. The retina has a high concentration of rod photoreceptor cells, which indicates their ability to see in low-light conditions. But the retina also has fewer cones, which explains their reduced color vision.
Another key difference between dogs and humans is the reflective tapetum lucidum. If you’ve never heard of this before, that’s because humans lack it entirely. The reflective tapetum lucidum is a layer of tissue in the back of the eye that helps reflect light after it’s already passed through the retina, which again enhances low-light vision. However, because the light gets scattered in the eye, finer details are harder to make out.
Dogs may also be able to perceive UV light in some way, although this has not been researched in depth. What we do know is that dogs have a lens that transmits significant amounts of UV rays.
The final major difference between the canine and human eye is a flavoprotein called cryptochrome 1. Sensitive to blue light, current research indicates that cryptochrome 1 may help dogs perceive the earth’s magnetic field. (Is this related to the study that found that dogs prefer to poop in alignment with the earth’s magnetic field? For some reason, not many studies have been conducted on the relationship between poop and vision, so this remains a mystery.)
Does Your Dog See Color?
Yes! The common myth–that dogs only see in shades of gray–has been debunked for a long time. And if nothing else, the presence of cones in their eyes indicates some ability to see color.
Although dogs most likely see fewer shades of color than we do, one older study indicated that dogs can distinguish between shades of gray that appear identical to humans. A more recent study found that dogs can discriminate between red, blue, yellow, and gray. Another theory suggests that while dogs can generally perceive color, they only react to colors with some biological significance to them.
If you’re trying to train your dog to distinguish between two similar objects, keep the limitations of their color vision in mind. Give them other indicators–context, shape, size, or scent–to help them along.
Can Your Dog See in the Dark?
At this point, it shouldn’t surprise you that the answer is yes–dogs can see in the dark, and much better than we can.
Even the ability to distinguish between different shades of gray points to their evolutionary history. In case you were wondering, wolves are crepuscular, meaning most active at dusk and dawn. No need to change your sleep patterns to better accommodate your pet, though–dogs are social sleepers, preferring to snooze when you do.
Although canine vision gets maligned in popular culture, all evidence indicates that we’re judging a fish for its ability to ride a bicycle, so to speak. Dogs may or may not be able to perceive color, but more importantly, why should they care about the difference between red and green? Next time you go on a late night walk, your dog might be squinting up at you, wondering why you seem oblivious to the squirrel moving through the branches above.
