When is a color not a color?
One of the main issues about the concept of color is whether color is a physical property of something in the world around us or whether it is a mental property which is not present in the external world. (1) I had always tended to take for granted that what I saw in front of my eyes was reality. Similarly, I assumed that color was an external property of the world; the red car that we are driving is universally red, the green tree is always green regardless of whether or not we are there to perceive it. However, upon entering this neurobiology class, I learned quite the opposite; according to what I have now been taught, there are in fact scientific theories that suggest that color is not an exterior property, but rather a construction of the brain completely independent of wavelengths. The fact that there could be two opposite theories, both with substantial and valid evidence supporting their claims, made me question the things that I so readily believed and lead me to investigate each side’s arguments in an attempt to make my own evaluation. I therefore looked into the arguments both of scientists who believed that color was and was not a physical property of the world presented and the research that they believed supported their claim. Their claims rely on elements such as research conducted which proves the existence of conscious color perception in certain blind patients, the existence of color constancy, afterimages and simultaneous color contrasts, and research suggesting that early visual experience is indispensable for normal color perception. This paper will first describe a few of the arguments in favor of color subjectivism and then compare them with research and studies that seem to indicate that there is wavelength realism to color in order to then come up with an opinion on which one must adequately describes color.
The theoretical analysis of color has undergone a considerable philosophical and neurobiological revival in recent years, as shown in the production of voluminous literature from both proponents and opponents of color subjectivism. The main argument that is often presented in favor of the internal nature of color is color constancy. According to these scientists, the apparent color of the surface depends as much on the composition of the light reflected from it as on that reflected from neighboring surfaces, such that its color tends to look the same regardless of the spectral content of the light in which it is viewed. (2) Although the colors in an image shift as available light intensifies or diminishes, people, as well as primates, usually recognize a particular hue throughout that change. For example, a ‘red’ apple will be perceived to be the same color on a sunny day as on a cloudy day. It is this phenomenon which is known as color constancy.
One of the more resent studies that have been conducted was led by Yoichi Sugita of the Neuroscience Research Institute, who explored color constancy in four macaque monkeys that had been raised from age 1 month to age 1 year in a room that was only illuminated by light with a highly restricted range of wavelengths to ensure that the animals could not discern the normal array of colors. (3) After age 1, the monkeys were not able to identify the colors they had just seen on a computer screen when the on-screen illumination of those colors changed, even after intensive training to overcome this problem, not were they able to recognize different shades of the same color illuminated to carrying degrees. In contrast, four other macaque monkeys that had been raised in a room that was illuminated by sunlight and fluorescent lamps were capable of recognizing colors in a variety of lighting conditions. The problems remained 9 months after the monkeys had been removed from their previous living space and placed in a room similar to the other monkeys. These results seem to indicate that early visual experience is an indispensable element of normal color perception, and that therefore color is a creation of our brains and minds. Obviously, it can be argued that the research is not truly valid because it was not tested on humans, but we cannot argue that it clearly demonstrates that animals can perceive color but that the lack the capacity for color constancy. This implies that it is the brain, and not the retina or any external, physical property that assumes responsibility for creating color in different lighting conditions.
Other scientists turn to elements of art to prove their point that color is not an external property of our world. They claim that the science of color must be regarded as a mental science and that whereas light energy might stimulate vision and our sense of color, it plays an extremely small role in the process of vision. Color, in fact, can be ‘seen without the excitation of wavelengths from the outside, such as in dreams, afterimages, pressure on the eyeball, or certain drugs such as LSD. In these instances, they claim that our sense of color remarkably operates from within our brains and psyche. There is also the issue of the effects of what artists call simultaneous contrast. This technique involves additive and subtractive color mixtures and the ability to make different stimuli give the same appearance and vice versa. In these situations, the brain is uniquely interpreting the raw information that the eye is sending. The question that cannot seem to be answered by a wavelength realism theory of color is how someone can create new non-spectral colors such as teal or maroon, which do not exist in the external, physical world, and yet be able to see and experience them. This fact seems to reinforce the viewpoint that color is a subjective neural process that is projected onto objects in the world.
There are, however, many scientists who claim that the reality of color is that it is a direct result of the reflection of wavelengths, and that therefore it is a property of the external world. D.M. Armstrong, in The Nature of Mind (1980), states that
“the real color of a surface is determined by the nature of the light-waves emitted from that surface. If a surface looks red, and is emitting light-waves of a sort or sorts characteristic of red surfaces, it is red. If it looks red, but it is not emitting such a sort or sorts of light-waves, it only looks red.” (p.109) (4)
This theory is interesting because it does not trivialize what the brain perceives but rather indicates a distinction between the ‘reality’ and ‘subjectivity of color’. To counter the arguments presented in afterimages and simultaneous color contrasts, this theory would seem to argue these things do not exist in themselves, but rather that they are experiences of these things; in short, in these situations there are processes occurring which are like the processes which occur when a real colored object is presented before us. Although it can be argued that what we perceive is automatically our reality because it is all that we are capable of knowing, it is intriguing to discover a theory that essentially refutes Emily Dickinson’s poem, which states that everything is contained in the brain, by suggesting that the reality of color is something that is physically independent of our nervous system.
A very interesting experiment was performed by Zeki et al. in 1999. In this experiment, they addressed the problem of the neural bases of color vision by considering a rare syndrome in which conscious color vision is largely preserved in an otherwise apparently blind subject. (2) The subject was capable of distinguishing even the shades of colors. He knew at once the colors of objects which he could neither name nor tell the form of. He behaved like other normal controls in his ability to name the colors of target objects and their surrounding patches when the stimulus array was illuminated with white light. However, when the spectral composition of the illuminant was changed, his responses varied with the reflected wavelength, unlike the normal controls. This study suggests that the subject’s conscious color vision is largely wavelength-based and does not use the mechanisms that subserve color constancy. (2) It also demonstrates that color vision and visual acuity can be disassociated in such a way that the former is intact whereas the latter is impaired.
I was hoping that by examining more closely the arguments and experiments presented by both those who support wavelength realism and those who support color subjectivism I would be able to arrive at a more educated, supported, and strong opinion of the concept of color. However, although I have certainly learned more about both issues, I have still not reached a verdict that I feel will do justice to the issue of color. Perhaps one of the greatest problems of science (and certainly of other subjects as well) is that there always seems to be the search for something that is universally and irrefutably correct; we seek one specific answer to many various questions without being willing to recognize the fact that perhaps there are many different answers, and that this in no way denigrates the question. It would seem to me that having only one of these theories deemed ‘adequate’ is not a sufficient explanation of color. Regardless of the nature of color or what it is a result of, it exists to most of us; regardless of the fact that some of us may not be able to see some or all color, we are all still capable of functioning. Perhaps our current models of color perception, therefore, should not be considered as being clearly defined and infallible concepts, but rather as outlines that still need to be colored in.
1. Wavelength Theory of Color Strikes Back: The Return of the Physical.
2. The Neurobiological Basis of Conscious Color Perception in a Blind Patient.
3. Sugita, Y. Experience in Early infancy is Indispensable for Color Perception. Current Biology, Vol. 14. (July 27 2004), pp. 1267-1271
4. Armstrong, D.M.: 1980, The Nature of Mind, University of Queensland Press, Brisbane.