Development of Human Color Perception According to Color Theories

The Evolution of Color

William Gladstone was a four-time prime minister of England and a Homer fanatic. In his extensive reading, Gladstone noticed the strange trends in Homer’s descriptions of color. Homer described seemingly simple things with “defective” words. Sheeps’ wool and iron were described as violet, honey was green, and the sea was “wine-dark”. In the Iliad and the Odyssey, the word black is used about 170 times in both books, white is used approximately 100 times, red is used about 13 times, yellow and green are under 10 times, and blue… zero times. The word “blue” is not used in any of Homer’s poems. But this phenomenon is not limited to Homer; when looking at other Greek writing, the same color trend was found and there was no mention of the color blue. Gladstone concluded that all Greeks were color blind and only able to see black, white, and a touch of red. Beyond that, the Greeks were straining to see colors, and over time, each generation developed better color vision than the generations prior.

But just as Gladstone had discovered that this trend was not unique to Homer, Lazarus Geiger found that this trend was not unique to the Greeks. This evolution of color exists cross-culturally. Geiger, a philologist, found this strange use of color in ancient Chinese texts, Vedic hymns, Icelandic sagas, and the Bible. This led Geiger to write, These hymns, of more than ten thousand lines, are brimming with descriptions of the heavens. Scarcely any subject is evoked more frequently. The sun and reddening dawn's play of color, day and night, cloud and lightning, the air and ether, all these are unfolded before us, again and again ... but there is one thing no one would ever learn from these ancient songs ... and that is that the sky is blue.

Given blue does not exist in these ancient texts but is a definitive part of human perception today, when did the color blue come into language? Although the exact date of each color entering language is not known, the order by which colors is not random. Each language begins with black and white, then red, then yellow, then green, and finally blue. Although there are some exceptions, one rule always holds true: red is the first color and blue is last. The color blue did not naturally exist in abundance in the ancient world. There are few blue animals, blue foods, or even blue flowers and the majority of blue flowers today are given the blue color artificially. Because people in the ancient world had not discovered how to make blue, they did not need a name for a color that they could not produce. On the other hand, the color red is easy to produce using clay. It seems that humans first gained the ability to perceive colors at low frequencies and long wavelengths and over time, adapted to see colors at higher frequencies and short wavelengths, so have humans evolved to perceive colors of higher frequencies?

Categorization of Color

In 1858, Geiger concluded that human development of words for colors stemmed from the ability of a certain color to be made reliably as a dye, but this is not just a theory of the past. Jules Davidoff, a professor of neuropsychology at London University, found a similar tendency in the Himba tribe of Namibia, who divide the color spectrum in a different manner than most. The Himba do not have a word to differentiate between green and blue and Davidoff created an experiment to test the tribe’s ability to perceive the difference between green and blue by showing them 12 colors, 11 of which were green and one of which was blue. To most people, there is no mistaking the greenness of the green or the blueness of the blue and the colors were completely different, but that was not true for the Himba. When shown the 12 colors and asked to which was different, they stared at the image without giving an answer. Davidoff examined each Himba participant’s eyes before the experiment, using individuals whose eyes were able to accurately sense colors. The Himba are not seeing different colors than the rest of the world, but they have a different system of categorization and are unable to perceive the difference between green and blue

When humans group objects, giving them name and meaning, the act of categorization feeds back on the brain’s perception so that the observer notices the thing in the category more. Conversely, it is hard to find something when one does not know what he or she is looking for. Without the word for blue, the Himba tribe sees blue as everyone else does, but they are not perceiving or noticing the blue. It is harder to spot since the blue does not jump out or call attention to itself; in other words, blue does not matter to the Himba. The sensation of color is the same, but the Himba language, culture, and experiences produced an individual visual experience than the rest of the world. Thus, to what extent can color perception be manipulated to exist uniquely to each individual?

The Color Spectrum - The Most Perfect Blue

Although our world does not naturally contain many blue things, our world is surrounded by blue. So how could anyone with the ability to see color not see the bluest blue? Guy Deutscher, a linguist and author, explored the blueness of the sky with his daughter, Alma, as she was learning to speak. Deutscher taught his daughter all the colors, but neither he nor his wife ever told their daughter that the sky was blue. Deutscher would point at objects and ask what color they were. At 18 months, Alma knew the colors, she knew what the sky was, and she was skilled at the color game. Deutscher began to ask what color the sky was; Alma had no answer, but rather looked up uncomprehendingly, answering, “What are you talking about?” Deutscher continued to ask the question, only asking it when the sky was clearly blue. The color game began when Alma was 18 months, and it was only when she was 23 months that she gave an answer: white. At 24 months, she finally said “blue” but not consistently. She would switch between white and blue until she decided the sky was blue, but that was only after she was “actively trained” to recognize specific hues colors as separate colors. Furthermore, Deutscher taught her that the sky had color by asking repeatedly what color the sky was. Without being “culturally indoctrinated”, she still had to be primed to decide the sky was blue. Homer most likely never saw a blue object, other than the sky and possibly, the sea and he was not constantly asked the color of the sky, nor was any other Greek at that time. It is understandable that someone who has not seen a blue object would not recognize the blueness of the sky.

Even the nature of the question is difficult; the sky is not a concrete object, but rather a vast expanse, a void, and emptiness. When children ask the question, “why is the sky blue” they may be asking why people say that the sky is blue, since Alma, and theoretically, other children do not perceive the sky as blue. So how could an empty space have color? What does it mean for something to have a color? 2.2 Color Spectrum - Light as a WaveAccording to Johann Wolfgang von Goethe, “Colours are light’s suffering and joy” and to some extent, that is accurate: Color is light or at least part of light. Newton famously experimented with the prism, by allowing the white light to travel through a prism, causing the light to “shatter” into a rainbow on the wall. He concluded that the rainbow of colors came from within the light, not the prism. The prism segmented the white light into its constituent parts, therefore, the white light is made up of all of the colors of the rainbow. Newton’s finding led to a deeper understanding of the nature of light as electromagnetic radiation moving in a wave-like motion. Although there are many characteristics of light, when discussing color, it is best described in terms of wavelength and frequency. These waves of energy range from gamma waves, with a high frequency and short wavelength, to radio waves, with low frequency and long wavelengths. The nature of light is a concrete, measurable, and object part of the process of vision.

Color Spectrum - Visible Spectrum

Visible light, or the light the human eye is sensitive to, is only a thin band of the entire electromagnetic spectrum, with wavelengths ranging from approximately 400 nanometers (nm) to 700 nm. Humans see the long wavelength, low-frequency light as a reddish color and the short wavelength, high-frequency light as a sort of blue. The frequency and wavelength have an inverse relationship and determine the hue of the color, while the amplitude of the wave determines intensity and brightness. When a color is composed of one specific wavelength, it is said to be a spectral color, meaning that it exists within the spectrum of visible light. Although a specific wavelength refers to a specific color, spectral colors do not exist in isolation as each spectral color gradually fades into the next, creating a continuous spectrum.

Color Spectrum - Defining Color

Newton also questioned whether color exists in the human brain or in the external world. Although color is considered a property of an object, the apple is perceived as red because it reflects red light and absorbs the other wavelengths of color. An object is white if it reflects all colors since white light is made of the wavelengths of color mixed together. An item is black if it absorbs all wavelengths of light. Under conditions of low light, the human eye is unable to activate color vision, so the silhouette of the apple would be seen in grayscale. So is the apple still red if it cannot be perceived as red? Colors do exist in the world since they can be measured as a wavelength of a spectrum, but to what extent is color an innate characteristic of an object? Given the sentence, “the apple is red in the dark room”, the verb “to be” is “having the state, quality, identity, nature, role, etc., specified”, according to the Oxford Dictionary. This is an active and continuous retention of the state, quality, identity, nature, or role specified. Even in a dark room, the apple maintains the ability to absorb and emit electromagnetic radiation and absent of the energy to create the physical response, the apple retains its ability to emit color. Color can be objectively measured by its structural capacity, and with modern technology, the subtle differences between colors can be observed as they relate to other colors. The intrinsic or extrinsic nature of color is dependent on the defined of color based on its practical use or innate characteristics. Color is a part of human perception, but the apple possesses the structural capacity to reflect electromagnetic waves with or without stimuli.

Biology - Transduction and the Brain

Although colors are waves of light, the electromagnetic radiation is translated into meaningful images by the eyes and the brain. Colors are forces of persuasion, communication, and symbolism, but between the external world and human perception, the spectrum of waves comes to life. Light is reflected off objects and travels through the eye until it reaches the retina, which is on the back of the eye and covered in photoreceptors. Photoreceptors are neurons that convert light into neural signals that stimulate biological responses in a process called transduction. Rods and cones are stimulated by light, sending a signal that goes through the ganglion cells, through the optic nerve, and the brain interprets the neural signals. Rods are located on the edges of retinas and contribute to peripheral vision. They are more sensitive to light than cones and function well in dim light on a grayscale from white to black. Cones are located near the center of the retina and specialize in perceiving color and fine detail. Although all cones can respond to all wavelengths in the visible spectrum, each type is most sensitive to one particular wavelength. However, they are not as sensitive as rods and need bright conditions to reach the activation threshold; therefore, humans lack color vision in a darkened room. When the rods and cones fire, they activate the ganglion cells which form the optic nerve. The optic nerve connects to the lateral geniculate nucleus (LGN) in the thalamus, sending messages to the visual cortices in the occipital lobes.

Biology - Sensation vs. Perception

Although there is a general consensus in the scientific community regarding the biological process of sight, it is not known where sensation becomes perception. Sensation and perception are connected but different. For example, someone may be born with an improper development of the retina, but the part of the brain responsible for perceiving the neural impulse is intact and capable. This is an example of when there is an innate problem in vision and the sense is inhibited, but the perception is intact. Someone with prosopagnosia is not able to recognize the faces of those they know and love. This face-blindness is not an issue of vision, but a problem with perception as the part of the brain responsible for facial recognition is unable to complete its task. Some researchers claim that perception begins in the occipital lobe, some claim it occurs in the LGN area, and others claim that it begins in the retina. Regardless of the location of perception, each individual's perception is manipulated by experiences, emotions, expectations, and cultural norms. The act of perceiving is the brain’s attempting to make sense of the pieces of information collected by the retina. The retina does not receive or process a full image, but rather, little pixels of energy that are translated into neurological impulses. Vision is the dominant sense in the collection of information from the world to create images and colors capable of conjuring memories, emotions, and desires that are unique to each person. Senses are merely raw data without perception and the brain’s ability to translate and organize the data is responsible for meaningful perceptions by combining color, intensity, depth, movement and more.

Color Theories – Trichromacy

The original color theory hypothesizes that the human eye contains three types of receptors which are stimulated by light in various combinations to create the visible spectrum. The three types of receptors are three cone types: red, green, and blue. This theory was proposed in the early 1800’s because it was understood that the human eye could not have an individual receptor for every different color. Even in the 1800’s, it was understood that humans could see thousands, if not millions of colors, so the human eye could not contain thousands or millions of photoreceptors spread across the retina. The Trichromatic Theory stated that all colors could be perceived by a combination of three receptors, so as an image falls on the retina, each receptor sends a separate color signal to the brain. Trichromacy refers to the three different color channels created by the three cones in the human eye. A blue cone responds to short wavelengths, thus are called s cones. Green cones are called m cones because of the peak sensitivity to medium wavelength. Red cones respond to longer wavelengths and are called l cones. The range of wavelengths to which cones respond overlap each other and in reality, peak sensitivities are not located at exactly blue, green, and red, and for this reason, it is more accurate to refer to them as s cones, m cones, and l cones respectively. As photons of light enter the eye through the cornea and pass through the lens, they reach the retina and trigger the cones to give off neural impulses. The specific color the brain perceives is dependent on the ratio of impulses from the various cones.

Visual Phenomenon

Although the Trichromatic Theory is supported and logical, the red, green, and blue cones do not create all the colors of the spectrum. If trichromatic processing were the only color processing system, the spectrum of colors would be much duller, lacking yellow, orange, magenta, and generally bright colors. In addition, the trichromatic theory is unable to explain phenomena such as afterimages and color blindness. Afterimages are demonstrated when an individual stares at one color for an extended period of time then looks at a blank white surface and sees the afterimage. If someone were to stare at yellow, the after image would be blue, and if someone were to stare at red, the afterimage would be green. Color blindness works in a similar way; if someone is a dichromat (someone with two, rather than three cones) they would be color blind to either green/red colors or blue/yellow colors. If someone were a monochromat, they would only be able to see variations of gray. These “color pairs” are not explained with trichromacy, thus a separate theory is needed to fully explain human color vision.

Opponent-Process Theory

The Opponent-Process Theory hypothesizes that colors come in opponent pairs of red-green, blue-yellow, and black-white. As red is stimulated, green is inhibited and as blue is stimulated, yellow is inhibited; these pairings are called opponent or opposing colors. This theory is based on the presence and lack of certain color combinations in ordinary perception as well as the nature of afterimages. Although humans are able to perceive orange as a combination of red and yellow, we cannot perceive a color that is a combination of the opponent colors, red and green; it simply does not exist. This is attributed to chromatic adaptation. As someone stares at a red image, the intense light of the particular wavelength striking the retina for an extended period of time causes the photoreceptors to tire and become bleached out. They have been so extended and stimulated that they are temporarily less sensitive to that wavelength, causing afterimages. This pairing of colors also explains color blindness because the colors come in sets and if someone lacks a pair, he or she is unable to see both colors of the pair. Dichromats lack one of the pairs, so he or she is unable to see either reds and greens or blues and yellows.

For years, the two theories were in constant competition until researchers found that both theories work together to further explain color perception. Trichromacy explains how cones work to absorb and interpret light while the opponent-process theory occurs in the other parts of the retina to sort and organize the information from the cones to be processed by the LGN. If color processing ended at trichromacy, humans would lack the ability to perceive many colors and would perceive a duller spectrum of colors. After Opponent-Processing, the spectrum that arrives at the LGN is much closer to human’s final color experience. After the final stage of processing in the cortex, the output of colors matches the final color experience as shown below.

Discernible Colors

Even though the process and interpretation of sensation into perception may be the same for the average person, the end result is unique to each person. This is revealed when quantifying the number of individual discernable colors. According to Calkins, humans can perceive 100,000 “discriminable colors”, but according to Kleiner, humans perceive 2.3 million colors. Myers claims the number is 7 million and Wyszechi claims 10 million. These numbers vary from person to person because of context, experience, memories, bodily state, and ability. Some people pay closer attention to detail, while others focus more on the big picture. An interior designer works with color in such a specialized way that they might notice just the smallest adjustments of hue, brightness, and intensity. Perceptions of color vary based on culture and upbringing and the types of color someone grew up around. Language and the capacity of words to describe things affect the way people communicate and understand color. In addition, biological factors create different perceptions of the world, such as the gradual deterioration of vision, whether it is due to cataracts, refractive errors, genetic lack of a cone, underdevelopment of the brain, optic neuritis, or strokes.

Uniqueness of Perception Based on Varying Sensations - Extrasensory Experiences

But biological processes can also enhance perception, such as the genetic mutation demonstrated by tetrachromats in which genes can mutate to form a fourth cone. However, the mere possession of this extra cone does not mean that someone with the fourth cone is able to see more colors. Humans have developed and constructed a world based on the fact that people are trichromats, so just as the people of the ancient world were unable to see blue, tetrachromats are generally not able to see more colors. They have not had the ability to practice this skill. So maybe someone has the ability to see extra colors, but if they have never the chance to use the skill or practice, that ability might lay dormant. The biological possession of the fourth cone does not correlate to the ability to perceive with the fourth cone. Just as correlation doesn't equal causation, the potential for sensation does not equate perception. Besides biological processes, neurological connections also enhance perception. For example, synesthesia is a neurological condition in which a person’s senses are connected so that someone might see sounds or hear colors. According to Dr. Veronica Gross of the University of Boston, synesthesia is involuntary but elicited, irrepressible, and stable. These specific types of mutations create perceptions that are unfathomable to someone who has not experienced the perceptions created by extra sensations; however, even without these extra abilities, everyone still experiences the world in an individual way.

Perception and Reality

The human eye gathers more information about the surrounding world than any other sense and is an integral part of human life. Color is one of the first things parents teach children and is a deciding factor in marketing and business and it affects customer behavior. Color acts as a symbol for holidays, religion, and political parties, but the sensation of color has no inherent meaning. It is what the brain does with that information. Color perception is unique to each person, and each person’s perception is his or her reality, but this personal reality is not reality. Color perception itself is limited and can be tricked or charged with a different point of focus, alternative lighting, and more. Humans have no direct access to the physical world without information from the retina and the brain does not see or sense reality but constructs reality based on the context and past experiences. Color perception is based on knowledge, learned facts or behaviors, and memories, and then the brain does the best it can to fill in the gaps, thus humans have an incomplete sense of reality. The eyes and brain can only understand and interpret a sliver of the electromagnetic spectrum. There is a gap between perception and reality. People think that they have an accurate representation of reality, claiming that he or she objectively knows. Each person has experiences, memories, and perceptions that are unique to them, making communication difficult. In recognizing the individuality of each person's perspective, in vision and in all things, people can begin to understand how much they do not understand. The acceptance of the uncertainty creates the possibility for greater understanding of how one person can hear, feel, and see the exact same information and perceive it in different ways as humans manipulate and interpret colors, senses, and the surrounding world through the same biological process, but with entirely unique perceptions.