Roses are red and violets are blue, but we only know that thanks to specialized cells in our eyes called cones. When light hits an object say, a banana the object absorbs some of the light and reflects the rest of it. Which wavelengths are reflected or absorbed depends on the properties of the object. For a ripe banana, wavelengths of about 570 to 580 nanometers bounce back. These are the wavelengths of yellow light. When you look at a banana, the wavelengths of reflected light determine what color you see. The light waves reflect off the banana s peel and hit the light-sensitive retina at the back of your eye. That s where cones come in. Cones are one type of photoreceptor, the tiny cells in the retina that respond to light. Most of us have 6 to 7 million cones, and almost all of them are concentrated on a 0. 3 millimeter spot on the retina called the fovea centralis. Not all of these cones are alike. About 64 percent of them respond most strongly to red light, while about a third are set off the most by green light. Another 2 percent respond strongest to blue light. When light from the banana hits the cones, it stimulates them to varying degrees. The resulting signal is zapped along the optic nerve to the visual cortex of the brain, which processes the information and returns with a color: yellow. Humans, with our three cone types, are better at discerning color than most mammals, but plenty of animals beat us out in the color vision department.
Many birds and fish have four types of cones, enabling them to see ultraviolet light, or light with wavelengths shorter than what the human eye can perceive. Some insects can also see in ultraviolet, which may help them see patterns on flowers that are completely invisible to us. To a bumblebee, those roses may not be so red after all.
Guest post by Sadie Steffens The paint color in our master bathroom has been a source of debate since we bought our house. While I am certain that the color is firmly in the purple part of the spectrum, my husband insists that the paint is blue. Period. Visiting friends have often been asked to weigh in on this debate, and the outcome is fascinatingly similar every time. When asking couples to cast their votes, men instantly declare the color to be blue. Women, on the other hand, typically pause before suggesting something like БperiwinkleБ or Бlavender blue. Б This phenomenon has been played out between men and women time and time againБfrom selecting clothing to disagreeing at the paint store about whether one hue of blue looks more purple than another. Although you may be tempted to write off this difference as a consequence of cultural conditioning, the true root is physiological.
Previous research has shown thatб Бthinkб periwinkle, azure, and other color names that are unlikely to be used by men in general conversation. But is this lack of color names the main reason for why men and women БseeБ color differently? Israel Abramov, a behavioral neuroscientist at CUNYБs Brooklyn College, doesnБt think so. HeБs curious about how wiring in the brain influences our perception of color. Do variations in connections explain perceptual differences between men and women? Three dimensions affect how we visualize color: hue, saturation, and brightness. б Hue б is the actual colorБred, yellow, green, or blue. б Saturation б is the deepness of the color: emerald green is more saturated than pastel green. Brightness б describes the way a color radiates or reflects light. asked men and women to break down the hue of a color and to assign a percentage to the categories red, yellow, green, and blue. The results showed that women were more adept at distinguishing between subtle gradations than were men. This sensitivity was most evident in the middle of the color spectrum. With hues that were mainly yellow or green, women were able to distinguish tiny differences between colors that looked identical to men. In fact, Abramov found that slightly longer wavelengths of light were required for men to see the same hues as womenБhues identified as orange by women were seen as more yellow by men.
However, when shown light and dark bars flickering on a screen,б. Men were better able to perceive changes in brightness across space, a skill useful for reading a letter on an eye chart or recognizing a face. This effect was increased as the bars narrowed, suggesting that men are more sensitive to fine details and rapid movement than women. These results suggest that the wiring differences in visual areas of the brain contribute to how men and women see differently, regardless of whether a person has an extensive vocabulary of color names. Sensory differences between sexes have been well studied. In the realms of,б , andб , women perform better than men at distinguishing between slight differences. levels may be the basis for these differences. Abramov believes that expression early in development plays a major role. Differences in testosterone levels promote drastically different organization of the neurons in the visual cortex in men and women. There areб б in the cerebral cortex (the part of the brain that processes information from the senses) than there are in regions of the brain associated with reproduction. Men have more testosterone receptors than women, especially in the visual region of the cerebral cortex.
The elements of vision that were measured in this study are determined by inputs from these specific sets of neurons in the primary visual cortex, so it makes sense that different numbers of receptors would result in differences in visual perception. Butб whyб do men and women perceive color differently? One potential explanation goes all the way back to the hunter-gatherer responsibilities of early nomadic tribes. As hunters, men needed to be able to distinguish between predators and prey from afar. On the other hand, women might have developed better close range vision from the act of foraging and gathering. Although further research is necessary, these visual differences could have consequences for how men and women perform at tasks such as art and athletics, where differences in near-vision and far-vision could be important. Regardless, we can be sure that the way we visualize color is somewhat different from person to person, as evidenced by Б Б that recently sparked much debate on the internet. (IБll admit, I was a misguided member of #whiteandgold). My husband and I are picking out colors for our guest room now. Although we disagree about whether the blue we chose is more green or more grey, at least we were both able to agree when we found the right color.