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We're back at it again, this time tackling that age-old question: are dogs colour blind? While we don't claim to be doggie optometrists, a little digging makes it plain to see that while dog vision isn't quite the same as ours, it's anything but a black and white proposition.
Dog and human eyes are made up of specialised cells and receptors called rods and cones. Rods help us detect motion and see in varying shades of light. Cones help us differentiate colours. Same-same so far, right?
But here's the difference. Humans have three types of cones, while dogs only have two. That makes them dichromatic (if you want to get real science-y about it). Humans can identify red, green and blue and various combinations of the three. But dogs, with their two cones, can only see shades of yellow and blue. Outside of that is a lot of shades of grey.
This makes dogs most similar to humans with red-green colourblindness.
Luckily experts in this sort of stuff have done plenty of research over the years to give us a better idea of what it's like to see the world through a dog's eyes. There's been a range of scientific studies on the structure and function of dog eyes to identify which cones they have and how these cones react to different wavelengths of light.
In some of these studies, dogs are trained to respond to colour cues for food rewards. By observing the dogs’ eyes and movement relative to coloured objects, these studies helped confirm that dogs only see in yellow and blue.
Other studies helped us figure out that dogs can't see quite as clearly or detect differences in brightness as well as we do. But that doesn't mean our pets aren’t bright themselves.
Despite what may seem like visual shortcomings, canine vision is actually better than ours in a few ways.
Dogs have rod-dominated retinas that allow them to see well in the dark. They can see more clearly in dimmer light, when there are more shades of grey and colour isn't as beneficial.
They are also more skilled at detecting moving objects, which explains why they see the ball better when it rolls across the ground compared to when it’s still.
It’s also important to remember your dog's senses of smell and hearing are far superior to ours. A dog’s hearing is around 4 times better than ours - they can hear higher frequencies and detect sound that is further away.
Dogs have highly sensitive noses with a sense of smell that is nearly 10,000 times more powerful than that of humans. They have nearly 300 million olfactory receptors compared to human noses' approximately 6 million. Dogs’ brains also analyse smell nearly 40 times better than humans. That allows them to see intense, vivid images through smell – something that's hard for us to even imagine. No wonder they follow their nose!
Dogs might not be able to see the world in the same bright, vibrant colour we can. But who needs 20:20 vision when you have superpower senses to help you seek out an old sock to chew, garbage bin to raid or siren to wail at.