Bored? Here, try this color vision game.
How’d it go? If it went poorly, don’t let the fact that you’re more mole than hawk get you down – this particular eye test isn’t exactly rigorously clinical. It’s also a better test of color sensitivity than it is of color vision. Still, it does put us onto an interesting topic: what is color vision? And why do some people seem more sensitive to color than others?
Color vision is the ability to distinguish different wavelengths or frequencies of light by perceiving them as colors. This ability largely comes courtesy of cones – tiny, light sensitive cells clustered at the back of our eyes.
When light enters the eye, it stimulates the cones (except in low-light situations, when rods take over, providing us with predominantly black-and-white night vision). There are three varieties of these cells in human eyes, each more sensitive to a given range of light frequencies.
For example, cones stimulated by relatively high-frequency light would largely responsible for our perception of violet, which rests at the high-frequency end of the visible spectrum. Cones stimulated by lower frequencies would pitch in more to our ability to see red.
These three varieties interact endlessly, giving rise to the incredible variety of color that we’re capable of seeing. And while there’s plenty of debate over whether we all see color the same way, the majority of humans have the same basic hardware: three different types of color-sensitive cells that feed information about light to our brains.
This range of three makes humans “trichromats” and while we might think our color vision’s great, it’s actually kind of lousy when compared to the rest of the animal kingdom. Granted, we are doing pretty well for mammals.
Most of our furry relatives are dichromats and only have two types cones. Dogs, actually, are a good example and while the old adage about their not having any color vision is a little unfair, they don’t stack up incredibly well against humans.
But that’s where our color perceiving advantages end. Many insects have vision at least on par with our own. Bees, for example, are trichromats, but perceive higher-frequency light than we do and see ultraviolet better than they do red, giving them the ability to accurately perceive potential feeding sites.
Reptiles, birds, and fish tend to be a cut or two above us, as many are tetrachromats or even higher. The current record holder for color vision, though, is actually a shrimp. Mantis shrimp have as many as 12 distinct types of receptor. They might not work identically to our own, but they still represent color vision on an entirely different level of complexity from what we have.
Even within our species, there’s plenty of variety. The one that you probably know most about is color blindness, a relatively common visual disorder. There are several types of human color-blindness, but the most common are various forms of functional dichromatism, in which an individual’s eye either doesn’t have a given type of cone cell, or has one cone variety that doesn’t function normally.
The result is generally an insensitivity to a given range of light. Red-green color blindness, the most widespread form of the disorder, makes it difficult for individuals to distinguish colors in the green-yellow-red range. Red hues will also be sharply dimmed, which can even make telling purple from blue difficult. Red-green colorblind individuals can even have a rough time picking up on red lights while driving, though most will develop various compensatory methods to work around this particular problem.
And while dichromats are the most abundant departure from the rule of three that you’ll find, there are also very rare monochromats, who can only perceive one shade (and effectively have total color blindness) as well as – intriguingly – tetrachromats.
This latter group is still a somewhat poorly understood one. Genetic quirks mean that it is possible for some women to have four simultaneously functioning types of cone cells. And indeed, in the past couple of years, researchers have identified women who do seem to have this extra visual boost.
However, whether or not this would say, help someone on the above vision game is up in the air. One identified tetrachromat does work as a painter and claims that her tetrachromacy has made her more sensitive to nuanced color in her work. Researchers have so far confirmed that she is a tetrachromat and have found that her extra cone species seems to react to light in the red-orange-yellow range, but aren’t entirely sure how or even if that affects her color vision on a practical level.
How About the Rest of Us?
Finally, we get down to variety between trichromats.
The first and probably the most wide-ranging difference you’re going to find is straight out of the battle of the sexes. Women have a genetically finer eye for color. A recent study from CUNY Brooklyn found that female participants were better at picking out small gradations in color – as in the game above – than men.
On the other hand, men were better at tracking moving objects. Israel Abramov, the study’s lead author, wasn’t entirely sure why this was, but hypothesized that it might have something to do with the fact that prehistoric humans may have divided labor, with men hunting (requiring sensitivity to motion) and women gathering (requiring sensitivity to color).
Conversely, poor color vision can be caused by a wide range of diseases and injuries. Glaucoma, cataracts, sickle-cell anemia, some pharmaceuticals, and alcoholism can all cause a reduction of color sensitivity. In fact, just about anything that causes widespread disruption to normal vision is probably going to have color vision at least a little out of order.
Still, if you flubbed out on that test, there’s no need to panic – just turning up your screen’s brightness could probably help. If you do find yourself having increasing difficulty distinguishing colors though, it may be time to head in for an eye exam.