Have you ever wondered what pets see and how it’s different than what we see? Find out what the world looks like to your pet and why.
Most pet owners have wondered, “What do cats see? What do dogs see? Is it the same as what I see?” The world looks very different to humans than it does to cats and dogs. For cats and dogs, the world looks slightly fuzzy, in shades of blue and yellow, and motion stands out more than anything else.
These big differences in vision come from very small differences in anatomy. At the back of the eye, a layer called the retina collects light for the brain to turn into images of the world. The retina is made of up cells called rods and cones — rods detect mostly dim light and motion, and cones detect mostly bright light and color. These cells play a significant role in how each species sees the world.
Light and Dark
The ancestors of today’s cats and dogs were crepuscular — that is, they hunted in the dim light of dawn and dusk, when their prey would also be most active. Therefore, both species evolved to see in dim and changing light. Cats’ eyes contain six to eight times more rods than humans, so they only need a sixth to an eighth as much light to see clearly. Dogs can see about half as well at night as cats — still four times better than humans.
Both dogs and cats have a tapetum, a layer of reflective cells behind the retina. Once light passes through the retina, it reflects off the tapetum and passes back through the retina so the rods and cones can receive even more light. This reflection also makes cats’ eyes appear to glow in the darkness when struck with a sudden light source.
Great night vision does not mean that cats and dogs have trouble seeing in daylight. Cats’ slit-shaped pupils allow them to adapt to almost any lighting. A cat’s iris, the part of the eye that expands and contracts to shrink or enlarge the pupil, is shaped like a figure eight and can close the pupil almost completely in bright light or open it to almost 90 percent of the eye’s diameter in darkness. On the other hand, humans still have an advantage in daylight; cats only have one-tenth as many cones as humans, which means that we see 10 to 12 times better in daylight.
In Living Color?
The old myth that cats and dogs can only see in black and white is not quite true. Your pet can see some colors, but not others.
Three types of cones exist for recognizing blue, red, and green light sources. Cats and dogs have very few red cones compared to humans, so they see the world mostly in shades of blue, gray, and yellow. Like humans with red-green colorblindness, dogs and cats cannot tell red, orange, yellow, and green apart.
This may sound like a strange way to see the world, because color is an important part of how we see, but dogs and cats rely more heavily on their senses of smell and hearing than humans do, and they are much more interested in shapes, brightness, and, above all, movement.
World of Motion
Even the most laid back dog or cat can trace its heritage back to some ancient hunter, and your pet’s vision is still built to spot scurrying prey — or a fast-moving toy. The same rods that detect dim light also help detect motion, and both cats and dogs have significantly more rods than cones. In terms of how they perceive the world, movement may be the single most important factor to both animals.
Dogs can spot even very slight motion, like the wave of a hand up to half a mile away. On the other hand, they often have trouble seeing stationary objects a few inches in front of their noses, which is why your dog may seem confused when you drop a treat right in front of him. Wiggle the treat a little, and his eyes will probably go right to it.
That happens because cats’ and dogs’ attention is drawn to movement by instinct. Motion in their peripheral vision may trigger a chase reflex unless your pet is very well trained, and both dogs and cats have excellent peripheral vision.
They also have a wider field of vision than humans. While we can see the 180 degrees or so in front of us, most cats can see about 200 degrees because their eyes protrude slightly outward, while ours are set farther back in our sockets. Dogs, whose eyes are closer to the sides of their heads, can see a field of vision of about 240 degrees, depending on the breed.
Not only do cats and dogs have a wider field of vision than humans, but they see things more quickly. Cats, dogs, and humans all see the world in a series of very quick still shots. The retina takes a fraction of a second to receive light and translate that into an image for the brain. For humans, this happens about 60 times per second. For dogs, it happens between 70 and 80 times per second (this measure of snapshots-per-second is called the flicker fusion frequency). The result is that when you throw a ball, it takes your dog a fraction of a second less than it takes you to see where it’s going, which is why dogs so rarely miss a catch.
This exceptional eye for movement is why most dogs have no interest in television, even when you turn on a dog food commercial. TV shows, videos, and movies are made up of a series of still images — they flicker across the screen at a rate just higher than our flicker fusion rate, so the image changes before we can see the gap between images, making it look like fluid motion. Because dogs have a higher flicker fusion rate, they do see those gaps, so TV just looks like a very quick slideshow of still photos.
A Bit of a Blur
Although cats and dogs are great at seeing motion, they are not so great at seeing small details. Dogs see with considerably lower accuracy and clarity compared to humans, and their vision has been compared to that of a middle-aged bifocal wearer, sans glasses. This is not a problem for dogs, because they mostly rely on smell for information about the world.
Cats, in particular, are slightly nearsighted. Humans can see quite clearly up to 100 or 200 feet away, but cat vision is at its best between 6 and 18 feet and not very clear at all past about 20 feet. Cats have trouble seeing things nearer than 6 inches or farther away than 20 feet because their eyes lack the muscles that would change the shape of the lenses, which change the distance at which the eye focuses.
Same World, Different Views
So, what do cats see? What do dogs see? They see the same world we see with different ranges and depths of color and motion. The next time you look at your pet, take a moment to imagine his view of the world.