Is it possible to conceive of another primary colour?

[fbsthreads]

can the human mind invent a new primary colour that is only in their minds, but they can actually picture it and envisage it.

the mind's concept of colour must be based purely on what we have seen.

heres another question, there is a lot we don't know about the universe, imagine if we discovered a new primary colour that we didn't know about, what would this do to our minds, that would allow us to envisage this new colour? and if we are capable of taking on board new colours, then why can't I imagine one?

 

[Polly]

I have had the same fascination since a kid. I still can't come up with anything.

 

[Janitor]

Neat question.

I hope one of the biological types will answer it.

My own guess is that the cells in the human retina have been subjected to a pretty wide range of wavelengths of e.m. radiation in various situations including maybe deliberate laboratory tests, and the only wavelengths that registered in the vision-processing part of the brain are the ones corresponding to the usual ROYGBIV colors that we know and love. I suppose it is barely possible that if you could stimulate the vision-processing part of the brain with electrodes, you might be able to set off the experience of some new, un-named color. But it's a long shot!

 

[motai]

I have had the same fascination since a kid. I still can't come up with anything.

Wow, you have too? I was ridiculed for asking these questions when I was younger (which IMO can lead to science). I have also wondered what some animals "see" when their spectrum is in the ultraviolet or infrared range.

 

[fbsthreads]

we could extend this idea further by thinking about what colour is like to people who were born blind.

how many colours do they have?
and if they have an operation to mend their eyesight, and it turns out they didn't have all the primary colours in their mind, what would the sudden inclusion of a new colour do to them?

 

[BlackVision]

When will the British and Canadians start spelling it color like it's suppose to be. :tongue2:

 

[Njorl]

Primary colors are arbitrary. Choose three frequencies of em radiation which, when heterodyned in different combinations can create any frequency and you have 3 primary "colors". They don't even need to be visible.

Njorl

 

[the number 42]

Janitor said "the only wavelengths that registered in the vision-processing part of the brain are the ones corresponding to the usual ROYGBIV colors", and I agree. I'd like to add that we have colour receptors (cones) in the retina too. These are filled will 3 pigments (red, green and blue, if memory serves). In colourblind people there may be a pigment that is faulty or missing, leading to less discrimination between colours. But even normally sighted people aren't equipped to see anything beyond ROYGBIV, in the same way that we can't fly as we don't have wings.

Hang on, we have hangliders, 747's etc - hmmm...

 

[zoobyshoe]

The phenomenon of color is completely created in the brain. There is no particular reason why different wavelengths of light should be perceived as anything other than shades of grey.

Oliver Sacks reported the case of a man who completely lost the ability to see color, as a result of an injury to a specific part of his brain. His eyes were unhurt. After this accident (in a car) the whole world changed to what he described as lead gray.

Since the brain creates color, it is concievable, although probably far fetched, that a drug, for example, might exite the brain to create a completely new color, inserted somewhere in the spectrum of visible light. We know so little about how the brain processes different wavelengths into different colors that this possibility can't be completely dismissed.

As it is, we are extremely lucky that our brains have evolved to create this mass hallucination we share called color, because it really makes the visual experience remarkably richer than it needs to be for our survival.

 

[Werdatothewise]

Part II

Part II

Mammalian Deficits

There are many other mammals with color vision. For example, diurnal squirrels and tree shrews have each been demonstrated to have at least two photoreceptor classes, and behavioral studies indicate that each meets the strict definition of color vision. Recent finds have also indicated that some rodents are sensitive to ultraviolet light, suggesting that they have a previously unknown class of photoreceptor. However, color vision systems do appear less frequently and with less complexity (i.e. with fewer photoreceptor classes) amongst species of mammals relative to species of most other classes of animal. To understand why this might be so, let's examine the history of mammalian evolution as evidenced by the fossil record, and conciliate that information with some comparative anatomy.

The lineage of animals which joins reptiles and mammals is often touted here as an excellent example of a transitional series. One detail that might seem surprising to people is that this transition occurred at the beginning of the Mesozoic era--the same time during which other reptiles were transitioning into dinosaurs. It's not quite right to say that mammals replaced dinosaurs at the beginning of the Cenozoic era, because mammals existed alongside of dinosaurs during the dinosaurs' entire "reign". However, during the Mesozoic era, dinosaurs and other reptilian cousins (e.g. pterosaurs, plesiosaurs and ichthyosaurs) were an extremely diverse group which occupied most of the available niches. The bush of life had only a small twig representing the lineages that would later branch out into all of the mammalian forms currently extant. Mesozoic mammals were small rodent-like creatures that were most probably nocturnal.

Note that the last paragraph is based only upon what we can glean from the fossil record. If current species arise from the descent with modification of pre-existing species, one might predict that the above inferred history of mammals would leave clues in contemporary mammalian anatomy. Oddly enough such clues exist.

Do we all agree that pretty much all animals are "color-blind" in the dark. Consequently, if an animal is only active at night a color vision system would be of little use, much as eyes are of little use to cave fish, moles and other animals which live in the absence of light. So if modern mammals are just descendents of the animals whose fossilized remains are found in Mesozoic strata, you would expect that this would be reflected in the makeup of their retinas. Lo and behold, this expectation is born out quite well.

First off, comparative anatomy indicates that most mammals don't have well developed color vision systems not because their line didn't get around to developing it, but more likely because after our ancestors evolved color vision it became superfluous and was lost. The color vision of primates is not strictly homologous to the color vision of fish, birds, turtles, etc. Much of the machinery used for primate color vision arose independently long after similar systems developed (without being lost) in other vertebrate lineages. At this point the wary creationist might say, "Aha! So primate color vision doesn't fit into the mammalian scheme, and could be construed as evidence of a creator--in developing primates, the creator used a feature similar to what he'd used in those other so-called 'lineages'". I urge anyone who might think this to look more deeply into comparative anatomy. I will only briefly describe a few relevant features here.

Color vision is mediated by cones, so named because of the shape of the receptive part of the cells. If the history of mammalian evolution described above were correct, you would expect to find significant differences between mammalian cones and the cones of other vertebrates. (The initial definition of "cone" vs. "rod" photoreceptors has some kinks, because it is apparent (based on criteria other than the shape of the receptive part of the cell) that some photoreceptors that appear on first glance to be homologous are actually analogous. For example, the "rods" of nocturnal geckos (a type of lizard) are most likely homologous to the cones of other animals--geckos did the opposite of mammals. In their development, geckos went through a strictly diurnal phase, and hence lost some of the adaptations for nocturnal vision. They subsequently became nocturnal again, and thus their cones faced some of the same adaptive pressures faced by the rods of other vertebrates.) Whether or not you expect it, this is exactly what has been found. There are several features that are quite common to the cones of non-mammalian vertebrates, but that are completely lacking in mammals. (As most of you might guess, there are exceptions to the "complete lack" of the characters I'm about to describe. I'll leave it as an exercise to the reader as to which animals are exceptions. I'll tell anyone who guesses and provides with their guess a rationale for why they guessed what they did. That is, if you understand and accept evolution, you would predict that if there are exceptions, they will be found in particular animals. If you don't understand or don't accept descent with modification as the origin of current species, I really would like to know what sort of reasoning you might use to guess at the exceptions.)

Many vertebrates have oil droplets at the bases of the light sensitive parts of their photoreceptors. These oil droplets often have pigments in them that absorb (i.e. filter out) some of the light that would otherwise stimulate the cell. What this does is to modify the spectral sensitivity of the photoreceptor bearing that droplet. This feature is not found in mammals.

Many vertebrates have double cones--two cones that are joined along their long axes by tight junctions, gap junctions or both. Nearly all classes of vertebrates have some variety of this form of receptor in their retinas. This feature is not found in mammals.

The photoreceptors of many vertebrates perform a sort of circadian dance. During the day, the rods are extended on long stalks so that their sensitive parts are buried in a layer of pigmented epithelium. This epithelium shields the rods so that very little light reaches them from the sides, and the cones basically shield them from axially propagating light. At night the cones are extended out into the pigmented epithelium, and the rods are contracted back to where the cones were during the day. This feature is not found in mammals.

The conclusion that might be drawn from the above is that there are many features of ancestral retinal anatomy that were retained in most classes of vertebrates, but lost in mammals. Elaborate color vision is just one such feature. The phylogenies of the opsin molecules that I discussed in the first post of this series suggest that mammals have always retained two cone pigments (a survey in 1981 indicated that there aren't any vertebrates with only one cone pigment), but any mammals that, like us, have more than two pigments (re)gained the third relatively recently (for us probably around 63 million years ago). [For those from sci.bio, this was why I was suggesting that squirrels might be trichromatic--I'm not willing to climb out on that limb now. Our short wave-sensitive or "blue" cone is probably homologous to the UV cone of other (i.e. non-squirrel) rodents. One of the inferred pigments in the dichromatic squirrels has about the same absorption spectrum as our short wave cone, so there isn't any reason to suppose that the squirrel has a third. That is, it is reasonable to conclude on current evidence that the UV sensitive rodents have the same cone classes as the squirrels, only their short wave pigment has been shifted to absorb even shorter wavelengths than those of most other mammals.]


How to See Red

In this final segment I'd like to address some of the probable steps required in the formation of a color vision system. I do this in an attempt to circumvent an argument via lack of imagination about the improbability of such a system arising more than once. The generation or elaboration of color vision systems is not a terribly complicated process (at least at the periphery).

Let's presume that we're starting with an organism that already has an eye of some sort. The first step towards a color vision system is the need for at least two visual pigments. It should be obvious that the addition of a pigment would be of immediate advantage even if the new pigment was expressed in the same cells as the older pigment(s). The reason is that there are some wavelengths of light where the new pigment will respond more strongly than the old, so the addition of a pigment will increase the animal's sensitivity over those wavelengths.

go to part III

 

[Werdatothewise]

Part III

The next step (conceptually anyways--it may be that this and the first step typically occur simultaneously) is the sequestration of the new pigment into a discrete population of photoreceptors. (By discrete, I don't mean spatially. I just mean that each photoreceptor should express only one opsin.) The advantage that this provides comes in the form of visual contrast. The lowest level of visual information processing is the recognition that something is different about a given region of space--i.e. that there is food or a predator "over there". To perform this function in habitats that are rich in light of particular wavelengths (the short wave "blues" underwater, or the mid wave "greens" of the tropical rainforest) it's best to have at least two pigments, one matched to the dominant wavelengths and one offset from those wavelengths. With the matched pigment, non-reflective objects have high contrast as dark areas on a bright background. With the offset pigment, reflective objects will apear bright against a darker background. Except in some extreme conditions (i.e. just above the aphotic zone for marine environments) the background probably isn't constant enough for that simplistic analysis to hold, but it's easy to imagine that if an animal has more photoreceptor classes it has a greater chance that one of them will allow for the visibility of a given target under a given set of background conditions.

(Note that it's not yet clear how the expression of photopigments is regulated in individual cells, but because of its accessibility, the retina is frequently used in studies of developmental neuroanatomy. Experiments with transgenic animals have already given us some key pieces of information about the regulatory mechanisms that determine what sort of photoreceptor a retinal precursor cell will become. Immuno- histochemistry has also been used to show that the fate of a cell, i.e. what sort of cell it will become, is established long before morphological differentiation is apparent. This is a hot area where the rest of this century is sure to see incredible advances in our knowledge base.)

The next step is the development of neural wiring in the retina that segregates the signals from one population of cells from those of the other(s). (Oddly enough this isn't necessary for the previous advantage, although as I'll describe below, there is good reason to suppose that these two steps occur simultaneously as a result of the mechanisms of neural development.) The advantage of this is that it allows the animal's retina to "draw" contours around an object (i.e. to place "color" boundaries on the visual scene).

The last phase in the development of color vision is the arrangement of wiring in the brain that allows an animal to segregate and classify objects according to their "color" (i.e. according to how well the object stimulates the different receptor classes). The advantage of this adaptation is that it allows the animal to classify objects according to "color". For example, it has been argued (although to me this is a just so story and may not be correct) that color vision and the expression of pigments in fruit co-evolved. That is, it is to the plants' advantage to have its fruit remain un-eaten until the seeds are ready for dispersal, so the color change in ripening fruit is a signal that the plants are sending to the animals. In turn the animal gets the greatest benefit from eating the ripened fruit, so it is to the animals' advantage to recognize when the fruit is ripe. The sort of comparison necessary for discriminating ripe from unripe fruit is easy if, for example, objects which reflect a lot more long than short wavelength visible radiation bring about a particular quality of sensation (e.g. what we call "red").

The point of the above was to make explicit that even if an animal were to develop color vision in steps, it's not hard to imagine a sequence of steps in which each step confers some advantage which would cause that step to be selected for. However, there's a beauty in the way that nervous systems are constructed which might lead you to expect that rudimentary color vision can arise in a "color blind" animal in only one or two steps.

The addition of a new pigment arises from a gene duplication followed by mutation of one (or both) of the copies. As indicated in the first part of this series, it seems pretty clear from gene sequence data that this is exactly how new pigments have arisen in us, fruit flies and a couple of other primates. By inference it seems likely that this is a widespread occurrence.

I'll end now with a brief foray into neurobiology. Animal nervous systems, particularly the nervous systems of vertebrates are not "hard-wired" at birth (or hatch or the end of metamorphosis...). Decisions about which nerve cells should be connected to which other nerve cells are made during a long space of time prior to adulthood, and in some animals (though usually to a much more limited extent) even during adulthood. Genetics seem to specify (in unknown ways) some of the gross features of connectivity--for example in mammals the axons of ganglion cells in the eye mostly grow through the optic nerve to a particular group of cells in the thalamus. However, the fine distinctions about, for instance, which ganglion cells connect to which cells in the thalamus are made initially by the formation of a lot of random connections. Many of these connections are then pruned back so that each ganglion cell stimulates only a small subset of the cells it initially connected with. The "rules" governing the pruning back are largely based on correlations in the activity of different cells--if two cells in the retina are generally active at the same time, then they will probably end up being connected to the same cells in the thalamus.

This activity-dependent pruning of connections appears to be the way that "maps" are created in higher brain areas. The best indicator of whether or not two cells in the retina will be simultaneously active, is how close they are to each other in space. Cells in the thalamus thus form a map of cells in the retina according to their activity, and hence their connectivity. Now it's easy to imagine that another determinant of whether or not two cells will be active at the same time is whether or not they are connected to cells which express the same pigment (within the retina, the same rules are followed in the creation of connections, so ganglion cells will preferentially be connected to cells which express the same pigment). So in the thalamus and other brain regions, there will be maps of the different receptor types within the maps of retinal location.

Of course neural development is a lot more complicated than I've described here, but the take home message is that the way that nervous systems develop in growing animals makes it easy to incorporate changes at the periphery. It has to be that way, or our nervous systems would not be able to cope with changes which occur in our muscles and sense organs as a result of growth.

If I've been at all clear, you'll see that once an animal has different photoreceptor classes the rest of the nervous system is already prepared to take advantage of them. An interesting case study in this regard is new world monkeys. In at least one species, two of their opsin genes are (like our mid- and long- wave sensitive opsins) on the X chromosome. The monkeys' expression patterns are different from ours, however, and it turns out that for one (or two depending on how you think about it) class of photoreceptor, the females can express the genes on each X chromosome. The males naturally only have one X chromosome. In the population, there are two types of male (depending on which allele they have on their X chromosome), and three types of female (depending on whether they are heterozygous, or homozygous for one or the other allele). The monkeys' developing nervous systems seem to take advantage of whatever photoreceptor classes happen to be out there in that animal's retina.

 

[Werdatothewise]

Part I

The topic is "evolution and color vision".

I'm going to start by describing a tiny fraction of what's well known about the molecular biology and biochemistry involved in visual transduction. If you're familiar with the topic, you may want to skip to the last couple of paragraphs in this post where I get to some data illuminating the evolutionary origins of the visual pigments. I intend to demonstrate how comparative anatomy makes sense in light of what the fossil record tells us about the history of mammalian evolution. Finally, in a fourth post I will outline some of the steps that would be required in order for an organism to acquire color vision, with a discussion of how reasonable it is to suppose that such systems could evolve multiple times.

Do "animals with color vision" should form a monophyletic group? In this context, saying that an animal has color vision is like saying an animal has a tail. Suggesting that two animals (say bees and humans) should be considered more closely related to each other than two others (say cats and humans) on the basis of the extent of their capacity for making color discriminations is similar to suggesting that two animals (say salamanders and lobsters) should be considered more closely related to each other than two others (say salamanders and frogs) just on the basis of which animals have tails.

What does it mean to say that an animal has color vision? The term color vision is used in different contexts with somewhat different meanings, but from our own perspective of what it means to see in color, the best definition would go something like:

An animal has color vision if it has the capability of discriminating lights (scattered light as well as light sources) on the basis of the lights' spectral content, even when those lights are of equal subjective brightness.

The front end requirement for such a system is that the animal must have at least two different spectral classes of receptor, where each class is defined by the sensitivity of the receptor to light as a function of wavelength. This often leads to a looser definition of color vision: an animal is declared to have color vision if it has at least two spectral classes of photoreceptor operating at the same time.

Although there are a variety of ways in which different receptor classes could be constructed, it seems that extant organisms use only one.

The first step in the transduction of light energy to a neural signal is the light-induced isomerization (change of shape) of a chromophore, specifically a vitamin A derivative. Each chromophore is bound to a membrane protein called an opsin. The main function of the opsin is to change shape after light absorption triggers the isomerization of the chromophore: the opsin is an enzyme that is activated by the chromophore's isomerization. However, because of the linkage between the opsin and the chromophore, the opsin also serves to tune the wavelength dependence of the light induced isomerization reaction in the chromophore. That is, the chromophore's sensitivity to light at a given wavelength is established in part by the opsin--different opsins (i.e. opsins with different amino acid sequences) bound to identical chromophores will have different absorption probabilities at each wavelength. The result is that photoreceptors which express the gene for only one type of opsin will form a different class than photoreceptors that express a gene coding for a different opsin. Although there are other mechanisms that animals could use to differentiate photoreceptor classes (most notably some animals use more than one chromophore, and many vertebrates have colored oil droplets that screen individual receptors) it seems that the expression of only one of their possible opsin coding genes in each receptor is the mechanism that all animals use.

Now we have to throw in a slight wrinkle. In a vast majority of vertebrates, there are two different sets of photoreceptors, one that operates during the day and another that operates in the dark. Most people are probably familiar with the distinction between rods and cones--rods mediate night vision, cones day. At night when the number of photons around is low, visual systems don't go to such fancy lengths to discriminate the light's spectral content, so there is generally only one class of rod in any given animal (at least some frogs are exceptions to this rule). For all intents and purposes, none of us have color vision when we're dark adapted. Thus with respect to vertebrates, the discussion of photoreceptor classes above was more specifically a discussion of cone classes.

Here we'll get to some interesting stuff by looking at the opsins for which we have the most data. DNA and peptide sequences for various opsins have been determined. In 1990, all of the then known amino acid sequences were compared in order to infer a phylogeny for the opsin molecules. These sequenced proteins consisted of four different opsins from drosophila, one from octopus, four from human (one rod, three cone) and one rod opsin each from chicken, sheep, cow, and mouse. All of the opsins have similar sequences, but any good evolutionary biologist could tell you that some should be more similar to each other than to others. Would anybody like to draw their guess at the phylogeny determined for these thirteen proteins? (Hint, it appears that all opsins derive from a very ancient protein, since it has homologs in bacteria as well as in both invertebrates and vertebrates. (I've recently stumbled onto a reference that claims that vertebrate rhodopsin and bacteriorhodopsin are not part of the same gene family. I'll reserve judgement until I've read more than just the abstract of the paper. Amongst vertebrates, the rod opsin seems to be the most conserved; cone opsins have arisen principally by duplication and subsequent mutation of the rod opsin gene.) Suffice it to say that these known opsins are not distributed in a mix and match fashion as one might guess a designer would have distributed them. If you'd like to see the phylogeny, you can look up the Goldsmith paper listed in the fourth post in this series. Alternatively I guess I could make an ASCII representation of it.

 

[Werdatothewise]

Part Ia

... continued from Part I

It should also be noted that many humans carry more than one copy of the middle wavelength-sensitive cone opsin. As this is grist for the evolution of color vision mill, we're literally ripe for the addition of a fourth cone class. (This probably won't happen, though, because people with a fourth cone class will be constantly trying to readjust the color on television sets. As a result of that such people will be highly selected against in bars the world over

Since 1990, a few other opsins have been sequenced, specifically opsins from a variety of monkeys. I don't know as that they've been compared with the others, but I'm willing to predict where they should fit into the picture. It's nice to have a theory that let's you do that. (Since I wrote this last paragraph, I've seen another phylogeny that I think had more than twice as many opsin sequences as my best current reference. As far as I know, that work is still in press, and I no longer have access to it. From what I saw, though, the creationists have even more reason to fold their hand on this one now than they did two years ago...)


Comparative Psychology

Prior to the advent of some nifty techniques in molecular biology, people had to use less direct methods of classifying photoreceptors. Among these methods are: direct measurement of the absorptive properties of individual receptors, measurement of the electrical responses of cells to monochromatic lights, and the conditioning of learned behaviors. Thus even without molecular biology, we knew (and know) a lot about the pigments underlying color vision systems.

Based on this sort of information, it's clear that most vertebrates have at least two cone classes. In fact, many birds, turtles and fish have four or five. Many invertebrates are similarly well endowed, and last I heard, the mantis shrimp was the winner of the contest of who has the largest number of photoreceptor classes. Given that coral reef animals and tropical birds often appear very colorful to us, it's not surprising that they have well developed systems of color vision. That different animals have different numbers of receptor classes already tells us that color vision systems are not all equivalent (as Bob might have us believe). If we restrict ourselves to animals which have the same number of receptor classes, might we expect that their color vision systems are equivalent?

The answer is a resounding no. Let's compare the color vision systems of two animals that both have three photopic (e.g. active under bright illumination) photoreceptor classes. One is the human, the other is the honey bee (specifically the worker--I don't know how the other castes are endowed). Does anybody here think that what a bee sees when it looks at a rainbow has the same appearance as what we see? We'll ignore optical polarization (which the bee is sensitive to and we're not) and focus on what we can infer about "color" based on, among other things, our knowledge of the bee's receptor classes. To begin with, at the inside of the rainbow where the violet-appearing light fades off to invisibility for us, the bee will still see more rainbow. On the outside, where we see red, the bee would see nothing for although bees have an ability to see what for us is UV, we have the ability to see what bees might call infrared.

Now picture that rainbow: what you see appears to have discrete bands of color. Don't for a minute think that those bands arise from there being anything discrete about the radiation emanating from that patch of sky. If you measured the radiation with a spectrophotometer, you'd find that the wavelength of maximum intensity as a function of the radial distance across the rainbow would decrease smoothly and monotonically from the outside to the inside of the bow. The apparent discreteness is an artifact of our photopigments (chromophore + opsin) and the neural processing of our photoreceptors' outputs. The bee too would probably see discrete bands (We can't ever really know how the world appears to a bee, but given what we can infer from doable experiments -- I actually chose the bee in part because its color vision has been studied about as much as any other animal's, excluding the human's -- the supposition that it would see discrete "color" bands from a rainbow is reasonable.) However, just as the outer and inner borders would be in different locations for us and bees (as described in the preceding paragraph), the borders of each "color" would be placed differently by the bee as well.

I can't claim that we have a good handle on why different animals have different visual pigments. There are some cases that are well understood--most notably it was predicted some 20 years before verification that marine fish that live just above the aphotic zone would have only one pigment, and that that one pigment would have a maximal sensitivity down around 450 nm (for us light at this wavelength would appear blue). It makes sense that if there isn't much light around, an animal's photoreceptors will be adapted to respond most strongly to the wavelengths of light most readily available. Bioluminescent fish and insects also tend to have pigments that are adapted for maximal sensitivity to the wavelengths of light emitted by their photophores (the molecules responsible for the emission of light e.g. from the abdomens of fireflies). The specifics of what selective advantage other pigments in other environments might convey are still somewhat mysterious

One thing is clear, however. The best known predictor of what sort of pigments will be expressed by any given animal, is the pigments expressed by its nearest living relatives. To an evolutionary biologist this makes a lot of sense, of course.

There are a lot of other differences (or similarities) between manifestations of color vision systems in different animals. I've chosen to stick to a discussion of pigments here partly for simplicity, and partly because the straightforwardness of analyzing retinal receptors makes this the facet of color vision about which the most data is available. The point of this post is to say that it makes no sense to use the presence or absence of color vision in determining a phylogeny. If you want to be serious about asking what color vision and evolution have to say about each other, you have to ask specific questions about what sort of color vision different animals have.

go to Part II

 

[hitssquad]

The affective component of sensation

Janitor said "the only wavelengths that registered in the vision-processing part of the brain are the ones corresponding to the usual ROYGBIV colors", and I agree. I'd like to add that we have colour receptors (cones) in the retina too.

This thread has nothing to do with sense organs. Sense organs do not have anything to do with feelings, whether those be heat, roughness, color, brightness, pitch, etc. If sense organs had anything to do with feelings, then there could be no such thing as synesthesia.

The original question was directed to whether or not we might be able to mentally feel a new color. The answer is that there is not enough information to rule out additional affective categories for colors, and it would be inconsistent to assume that our three color affective categories define a limit, so therefore there should be a possibility for more.

However, this directs our attention to what it means to have distinct affective sensations and how these distinct affective sensations are created in our minds.

 

[the number 42]

Steady on - I didn't post the essay

Obviously this is conjecture, but I would suggest that due to the limits of our sense organs we are capable of only 'feeling' a certain range of colours, whether we mix these colours up with sounds or any of the other senses. This would be because our cognitive capacity has evolved in tandem with the processing of information from the organs that feed the information to it. The question then might be: 'Given that the brain evolves more quickly than other parts of the body, how can we get it to expand to process information beyond our usual range of senses?' Or it could be that certain 'sensitives' already have this ability, in the same way that some people are born unusually tall.

Also, I don't think we can just mentally feel things; I believe feelings are a physical as well as mental event.

 

[zoobyshoe]

The original question was directed to whether or not we might be able to mentally feel a new color.

No. There were two questions. The first was whether or not it was possible to imagine a new color. The second was a question about how our minds would adapt if we were confronted with the discovery of an authentic new color.

The questions weren't about people's emotional reactions to color.

However, this directs our attention to what it means to have distinct affective sensations and how these distinct affective sensations are created in our minds.

They know a fair amount about this already. The organs of the limbic system of the brain have been proven to be the pivotal location where the physiological things we feel when we experience an emotion are orchestrated. They know, for instance that two little almond shaped things called the amydala are responsible for fear and also agression. I don't recall the details just now, but I read that crying is generated in one hemisphere exclusively, while laughter is generated in the other. (can't remember which is where, though). The hypothalami are two important parts of the limic system that both control some emotions and also most of the autonomic functions: heart rate, breathing, blood pressure, shivering, etc.: all that stuff we don't consciously control. I have seen charts that map out the whole process from perception of outside stimuli to signals sent from the brain to the body telling it how to react. It is quite complex. The endocrine system is involved, hormones are released, feedback loops are developed.

 

[the number 42]

There you go again, Shoe, with your fancy book-learnin' :grumpy:

 

[hitssquad]

Bradley Rhodes and affective vision

No. There were two questions. The first was whether or not it was possible to imagine a new color. The second was a question about how our minds would adapt if we were confronted with the discovery of an authentic new color.

Breaking this into two questions doesn't make sense. We have been confronted with new the discovery of wavelengths outside of our vision range, and this has apparently not had an impact on our affective sensations of color. You may be familiar with Bradley Rhodes' development of a system for seeing the variations in wavelengths that lie within the visible spectrum, but that we are normally unable to detect (he gives the example that two sheets of paper may appear identical to us humans, but very different to a spectrometer). His system uses aural feedback to transmit the data to the user, and allows people to "see" discrete details of their environments that would otherwise be invisible. there are two aspects to Rhodes' research that are apropos to our discussion. The first is that it overcomes a limitation in vision receptors, where our human vision receptors respond with the exact same signals over broad ranges of wavelength. The second is that it overcomes an affective limitation whereby we have only affective sensibilities of three "colors."

The questions weren't about people's emotional reactions to color.

They apparently were about people's affective sensations of color, as I stated.

 

[zoobyshoe]

Breaking this into two questions doesn't make sense.

Fbstthreads asked two questions:

can the human mind invent a new primary colour that is only in their minds, but they can actually picture it and envisage it.

the mind's concept of colour must be based purely on what we have seen.

heres another question, there is a lot we don't know about the universe, imagine if we discovered a new primary colour that we didn't know about, what would this do to our minds, that would allow us to envisage this new colour? and if we are capable of taking on board new colours, then why can't I imagine one?

The first, to paraphrase, was whether or not we can immagine a new primary color. The second, the one he preceeded by the words "heres another question...," was one about how our minds would adapt to accommodate a newly discovered color.

The word affective means: relating to, arising from, or influencing feelings or emotions.

fbstthreads, however, as you can plainly see if you reread his post, which I have quoted in it's entirety for you to do, was not asking about affective responses to color.

They apparently were about people's affective sensations of color, as I stated.

I think your problem may be with the words affective and sensation. The fact you put them together in the term "affective sensation" suggest to me you are unclear about what one or both of them mean.

 

[zoobyshoe]

There you go again, Shoe, with your fancy book-learnin' :grumpy:

Well, I done read a book, once, an the feller what wrote it had all them ansers, but I fergit what he said jus' now.

 

[selfAdjoint]

To me "affective sensation" is what you have when you look at someone you love. Or hate. And yes I mean it in the technical sense of both words.

How about hearing someone recite Ozymandias really well?

 

[zoobyshoe]

To me "affective sensation" is what you have when you look at someone you love. Or hate. And yes I mean it in the technical sense of both words.

Yeah, the babes really love it when you talk to them about your affective sensations.


Seriously: To me, pairing them is a redundancy. To say you feel an emotion is de facto to be reporting a sensation. If whatever's going on in your mind doesn't translate to the body, you won't experience an emotion. "Affective sensation" strikes my ear like "I'm having an emotional feeling." Infelicitous.

 

[BobG]

can the human mind invent a new primary colour that is only in their minds, but they can actually picture it and envisage it.

the mind's concept of colour must be based purely on what we have seen.

heres another question, there is a lot we don't know about the universe, imagine if we discovered a new primary colour that we didn't know about, what would this do to our minds, that would allow us to envisage this new colour? and if we are capable of taking on board new colours, then why can't I imagine one?

How many people wonder why they put the word 'yellow' on cans of tennis balls?

There are no primary colors, just a continuous spectrum, but I think the second point about the mind's concept of color is the more important point. The missing point is how a person exposed to a new 'color' could convey that color to anyone.

The ROYGBIV scale is only used in science, and even then, the assigned frequencies for each color are only approximate. For a better clue as to human color perception, you should look at languages. Some languages have only three 'primary' colors and some have four. None have seven. English has four: red, yellow, green, blue. French has three: red, yellow, and blue. The non-primary colors are comparitive additions (the same shade of yellow that an orange is; the same shade of blue that a violet is).

When it comes to being able to perceive enough difference between frequencies to assign a particular color, each person's is a little different, so it's not that advantageous to divide the spectrum up into too many small slices when referring to it in a language. The frequency used for tennis balls is one case in point. Most perceive that shade as yellow while a small minority perceive it as green.

Two people don't even necessarily have the same range of color perception. I think the shortest wave length perceived by a human is a little over 300 nm and the longest a little over 1000 (normal is about 390 nm to 780 nm). So some people do perceive 'colors' that the rest of us don't see, but you don't see them inventing a new word for those colors. Some may not even realize they're seeing any extra colors (or that they might be missing the bottom or top of the color spectrum) - they just lump it in with red or blue (violet).

To realize a 'new' color, a person would have to have some sort of enhancement that suddenly improved their range or some sort of change that shifted their sensitivity (so 640 nm suddenly looks red instead of orange - hey!, now that you mention it, were the Denver Broncos old uniforms really orange? I always heard that Orange Crush nickname and kind of held my head a little sideways and thought, "maybe kind of an orangish tinted red if you look at it just right", but I always thought calling those jerseys orange was a pretty big stretch).

 

[zoobyshoe]

Bob,

What do you make of the remarkably large list of color names used among artists and designers, and even women in general (generally in reference to clothing)? How is it that most women know the difference bewteen "lavender" and "lilac" and between "aquamarine" and "light aqua".

I ask because it seems to me that, in the absence of true partial colorblindness, I don't see any evidence to support the notion some people may be seeing colors differently than other people.

 

[the number 42]

Don't worry everyone, I have found the answer. I is possible to see another primary colour, and it is called grellowange. We can all see it if we simply relax, and try really hard. It is very nice indeed, and amazing that we haven't seen it before. It is totally unlike any colour you have ever seen. In fact it is more of a feeling than a colour...

...in fact it may just be a feeling. (Damn).

Okay: I have a feeling there is new colour. Ignore what I have just written above, as it may not stand up to rigorous scientific scrutiny. I would like to announce that I feel that the new colour is called grellowange, and has the texture of silk, and smells kind of funky, looks like a squirrel, moves like a wombat, but don't take my word for it, check it out for yourselves.

 

[Gza]

Last year after ingesting around an eighth of shrooms as a part of an "experimental phase" of mine (not talking physics lab here), I looked at the rug on my floor, which always usually seemed very ordinary looking, but this time I looked, I noticed visual perceptions I had never seen before, including color signals outside of my previous range of sight. That impressed me to the point where I decided to write a few pages about my experience while still tripping, but ended up scrapping it the next morning when I realized it made no sense whatsoever. I can still see the impression of the color(if that's what you can call it) in my sober mind, but have no chance of trying to explain it to someone whos never seen it.

 

[zoobyshoe]

Wow, Gza, I speculated about that very possibility earlier:

Since the brain creates color, it is concievable, although probably far fetched, that a drug, for example, might exite the brain to create a completely new color, inserted somewhere in the spectrum of visible light.

 

[BobG]

Bob,

What do you make of the remarkably large list of color names used among artists and designers, and even women in general (generally in reference to clothing)? How is it that most women know the difference bewteen "lavender" and "lilac" and between "aquamarine" and "light aqua".

I ask because it seems to me that, in the absence of true partial colorblindness, I don't see any evidence to support the notion some people may be seeing colors differently than other people.

They must spend more time looking at those little paint charts than I do. Like anything else, most people can improve their color perception through practice, or just by being more interested.

Personally, there's no way I could tell the difference between those shades and I don't think that's uncommon. (However, water running down a river/creek has never looked quite the same since I started rafting/kayaking. I focus on different aspects than I did before.) I think the average person might look at a painting or a room and be able to feel the mood created by the choice of colors, but I don't think the average person really pays enough attention to color to name individual shades that are presented independently to as much detail as is presented on those little paint samples at the paint store.

 

[the number 42]

can the human mind invent a new primary colour that is only in their minds, but they can actually picture it and envisage it.

the mind's concept of colour must be based purely on what we have seen.

heres another question, there is a lot we don't know about the universe, imagine if we discovered a new primary colour that we didn't know about, what would this do to our minds, that would allow us to envisage this new colour? and if we are capable of taking on board new colours, then why can't I imagine one?

most people can improve their color perception through practice, or just by being more interested.

Its probably true that some people can discriminate between shades more accurately than others, but we have downgraded somewhat from the original question of whether we can see a new colour (primary, secondary, tertiary, or haliberry).

If anyone can give an affirmative answer to this question, the explanation would probably be as unfathomable as the colour would be unseeable.

 

[NateTG]

The first question to ask is, what are primary colors?

The primary colors for normal humans are:
Red Green and Blue.

This corresponds to the color sensors in the human eye.

And the secondary colors are:
Yellow (Red + Green)
Pink (Red + Blue)
Cyan (Blue + Green)

For certain types of color-blind men people the primary colors are:
Red(A) + Red(B) + Blue
as a consequence, these people do not distinguish between pink and cyan, or yellow and red well.

This is the result of a mutation in the genes for the green cones. Since these genes are on the sex chromosomes, color blindness is gender related. In effect, women have six different types of cone, while men only have three.

A typical woman would have two types of red, green and blue receptors. In a study, scientists in England found a womant that could distinguish between colors in a way that indicated that her primary colors were:
Red(A), Red(B), Green, and Blue.

She claimed to have uncommonly good color sense as well.

Clearly it's possible to have a fourth primarly color. Whether it's possible to accurately imagine the difference in experience is much more difficult.

 

[zoobyshoe]

They must spend more time looking at those little paint charts than I do. Like anything else, most people can improve their color perception through practice, or just by being more interested.

This is part of my point. If people can be trained to pay attention to, and name, and remember subtle differences in color, it strongly suggests that we all do see color pretty much the same. This kind of goes against your speculation that we might be experiencing greater differences in color perception than we realize (except in the case of undiagnosed partial color-blindness).

I think if I showed you something ecru and something tan side by side, you'd have no problem seeing the difference. Becoming conversant with all the terms is a matter of constant working with them. Perception of the differences, whether you can name them or not, is already in place.

 

[BobG]

Yes and no, kind of.

Everyone has a slightly different average body temperature and their actual body temperature varies over the course of the day, or even the course of the month. But everyone's average body temperature is close enough that a funtional 'normal' body temperature can be established by just rounding up to 37 degrees celsius (the average average body temperature is closer to 36.8).

Even though a person's average body temperature may be lower than the average person, they can still sense most significant differences in their own body temperature.

As long as everyone's vision range is pretty close to the norm and their ability to distinguish colors is pretty close to the norm and colors are described fairly generically (red, yellow, green, blue), how could they tell that it doesn't quite match the 'defined' wavelength for each color.

Functionally, there's almost no difference. The differences in color perception from person to person is very subtle and there's only a few people who's range is skewed just the right amount from the norm to have 'peculiar' quirks that only become evident towards the edge of an accepted range for a given color.

And, logically, considering just about everyone's average body temperature, voice, height, weight, ability to hear (perfect pitch, for example) are all slightly different, I'd be surprised to find out every human's vision is exactly the same. (Which probably makes me slightly biased towards believing the articles that say people's color perception varies.)

 

[donnie]

Good stuff.
Consider the colour of water.