The popular notion that dog vision is only black and white is dead wrong. Our four-legged friends’ eyes are much more complex and although they see differently than we do, they can see a combination of colors that clearly differentiate yellow and blue. Technicolor is certainly beyond their comprehension, but there’s more to it than sad, fuzzy grays.
A yellow and blue world
Over the past few decades, studies of the structure of the dog’s eye have revealed some differences in basic design between humans and dogs. Canids evolved their senses as nocturnal hunters, tracking and catching their food at night. Therefore, their eyes have adapted to see well in the dark and to detect movement. “They have a larger lens and corneal surface area and a reflective membrane known as the tapetum that improves night vision,” explains vet Jerry Klein. “They also have more rods in their retinas, which improves vision in low light.” According to research conducted by the University of Washington Department of Ophthalmology, a dog’s color vision is more similar to that of a person with color blindness, but with the difference that it can distinguish yellow and blue and all combinations of these colors. This turns much of their world drab. A lush green lawn will look like a hayfield to them, while a red velvet cushion might be a cozy patch of brown. It’s not for nothing that dogs are crazy about tennis balls and are definitely more interested in yellow and blue games than in other colored ones.
Photo credit: Dog Vision // American Kennel Club
look at the movement
But how does the dog mind reconstruct what it sees? Scientists from Emory University attempted to answer this question using a machine learning algorithm capable of analyzing the information gleaned from the magnetic resonances of two “volunteers”. The protagonists of The Dog Project study, published in the Journal of Visualized Experiments, were Daisy and Bhubo: two mestizos who watched video for a total of 90 minutes over three sessions while their neural data was recorded. From the analyses, the researchers found that dogs “are more in tune with what’s happening in their environment than with the subjects responsible for the actions.” This underscores the major differences in how the human and canine brains work. “We’re very object-oriented,” explains author Gregory Berns, “while dogs seem to be more attentive to the plot than the subject at hand. Dogs only see in blues and yellows, but have a slightly higher density of visual receptors designed to detect movement. On closer inspection, these results make sense: Our four-legged friends are evolutionarily and instinctively inclined to pay attention to what’s happening in the environment in order to know what to do or where to go. Action and movement are fundamental”.
Unknown colors
There is also evidence that dogs can see colors that humans cannot. A study from City University London, published in the journal Proceedings of the Royal Society, explains that a dog’s eyes are more sensitive to ultraviolet light than humans, making it possible to see colors unknown to us. The only drawback is the sharpness: In the study published in Plos by the University of Linköping, Sweden, the visual acuity of dogs was subjected to tests similar to those that ophthalmologists carry out on humans. And the result was that the dogs — or at least the pugs and Scottish Shetland Sheepdog that took part in the experiments — were downright short-sighted, with around 20/50 vision. That means they have to be 6 meters away from something to see it the way a human sees it 15 meters away.
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