How Animals See the World
BY ELIZABETH PRESTON
ome animals, including your pets, may be partially colorblind, and yet certain aspects of their vision are superior to your own. Living creatures’ visual perception of the surrounding world depends on how their eyes process light. Humans are trichromats—meaning that our eyes have three types of the photoreceptors known as cone cells, which are sensitive to the colors red, green, and blue. A different type of photoreceptors, called rods, detect small amounts of light; this allows us to see in the dark. Animals process light differently—some creatures have only two types of photoreceptors, which renders them partially colorblind, some have four, which enables them to see ultraviolet light, and others can detect polarized light, meaning light waves that are oscillating in the same plane.
“None of us can resist thinking that we can imagine what another animal is thinking,” says Thomas Cronin, a professor at the University of Maryland who studies visual physiology. But while guessing animals’ thoughts is a fantasy, looking at the world through their eyes is possible.
Cat
“We will never know what a cat would experience,” says Dan-Eric Nilsson, a zoology professor at the University of Lund in Sweden and coauthor of the book Animal Eyes. But we can come close to seeing what it sees. Unlike humans, cats are dichromats; they have only two kinds of cones in their retinas. They see similarly to humans with red-green colorblindness, Nilsson says. To model a cat’s vision, one has to pool everything that’s red or green into one color.
The cat’s eyesight has a lower resolution than our own, which means it sees objects slightly blurrier than we do. Human vision is among the sharpest of all animals, thanks to densely packed cones at the center of our retina. Nilsson says cats’ daylight vision is about six times blurrier than ours, which is not depicted in the image above. However, cats have more rods than humans, so by moonlight, the advantage is reversed.
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