Color is an integral part of human life. We use paint colors to change the atmosphere of our homes, colored lights to control traffic, and even different colored clothes to display our professions.
While not everyone can see life in technicolor, as discussed in “Understanding Color Blindness“, many people make decisions and experience emotions based on color every day. So how does color vision work? And are there versions of color vision that differ dramatically from the average human experience?
Color Vision in Humans
All colors appear because of how light interacts with objects. When you see a distinctly colored object, the color you see results from said object absorbing all the other colors of light. For example, grass appears green because it absorbs all light that isn’t in the 577 to 492 range and the sky appears blue because it absorbs all light that isn’t in the 492 to 455 range.
Your eye processes colors in the retina, a membrane found at the back of the eyeball. The retina contains six to seven million tiny cells that translate the light that comes into your eyes into recognizable color information that’s then sent to your brain.
Cells that perform this function are known as photoreceptors. In the retina, most photoreceptors fall into a class of cell called cones. Cones can be three different lengths, short, medium, and long. These cones are referred to as s-cones, m-cones, and l-cones respectively. Each cone length detects different light wavelengths. S-cones react to blue wavelengths, m-cones respond to green wavelengths, and l-cones process red wavelengths.
The average human has significantly more l-cones than s- or m-cones. A little more than 60% of the cones in your retina are dedicated to red light wavelengths, while only 2% react to blue light wavelengths.
This cone configuration allows humans to see the entire rainbow of colors, but we can’t see wavelengths that are shorter than 390 or longer than 622. Ultraviolet light and X-rays are both shorter than 390, while radio waves and infrared are longer than 622. We can’t see these light wavelengths without the help of special equipment, but scientists suspect that some animals can.
Color Vision in the Animal Kingdom
The types of color vision that differ from the average human’s belong to the animal kingdom. Many animals see fewer colors than we do, but scientists believe that some animals can see even more of the spectrum due to the presence of more color cone varieties in their retinas.
Your pets and other animals experience the world in a drastically different color palette than yours. Most animal’s color vision either lack the color red or have the addition to see the ultraviolet spectrum.
No L-Cones
Without color cones that react to red light, some animals see a similar color palette to people with red-green colorblindness. This palette includes a range of grays, blues, and yellows and looks similar to light sepia.
Animals that don’t have l-cone photoreceptors include:
- All cattle, including fighting bulls
- Cats and dogs
- Rodents, like rabbits, rats, mice, and hamsters
Many human activities performed with these animals involve a misconception that the animal sees color as well as we do. For example, fighting bulls charge at a matador’s cape because the fabric is moving, not because it’s red. Similarly, your cat may chase a red laser pointer dot because it resembles the movement of prey, not because it has an eye-catching color.
Four Cones
Most animals that have more types of color cones than humans have four types of color cones. The additional cone type is shorter than our s-cone, so scientists believe that this extra cone allows animals to see ultraviolet light.
Animals with four cones include insects, like honeybees and butterflies. Scientists believe that these insects evolved better color vision than humans in order to help them see pollen sources.
It’s also possible that there are even more variations on color vision in the animal kingdom. For example, the mantis shrimp’s eyes have 16 different types of color cones. These crustaceans can potentially see colors and color details that humans cannot even comprehend.
It’s important to remember that color vision does not necessarily affect visual acuity. For example, a cat may not be able to see red-colored object the way you do, but a feline may be able to spot movement at a greater distance than you can. And a bee might see ultraviolet patterns on flowers, but that doesn’t mean the insect has great eyesight overall.
You may be stuck with normal human eyesight, but if you think you may be colorblind or if your color vision changes, make an appointment at the All About Eyes location nearest you. Our eye doctors can perform tests to evaluate a color vision deficiency and determine whether your color blindness indicates any serious underlying problems.