Tag Archives: colour

A look at colour

Judith Copithorne image

Judith Copithorne image

Back to the OpenMIND collection and a paper on colour vision (Visual Adaptation to a Remapped Spectrum – Grush, Jaswal, Knoepfler, Brovold) (here). The study has some shortcomings which the authors point out. “A number of factors distinguish the current study from an appropriately run and controlled psychological experiment. The small n and the fact that both subjects were also investigators in the study are perhaps the two most significant differences. These limitations were forced by a variety of factors, including the unusual degree of hardship faced by subjects, our relatively small budget, and the fact that this protocol had never been tried before. Because of these limitations, the experiments and results we report here are intended to be taken only as preliminary results—as something like a pilot study. Even so, the results, we believe, are quite interesting and suggestive.” To quote Chesterton, if it is worth doing it is worth doing poorly.

The researchers used LCD goggles driven by a video camera so that the scene the subject saw was shifted in colour. The shift was 120 degrees of a colour wheel (red to blue, green to red, yellow to purple). The result was blue tomatoes, lilac people, and green sky. (video) The study lasted a week with one subject wearing the gear all the time he was not in the dark while the other wore the gear for several hours each day and had normal vision the rest of the time. How did they adapt to the change in colour?

Colour consistency is an automatic correction the visual system makes so that colours do not change under different light conditions. Colours do not appear to change when viewed in sunlight, twilight, candle light, fluorescent lamps etc. What perception is aiming at is the characteristic of the surface that is reflecting the light and not the nature of the light. Ordinarily we are completely unaware of this correction. The colour shifting gear disrupted colour consistency until the visual system adapted to the new spectrum.

We did not test color constancy in any controlled way, but the subjective reports are quite nmistakable. Subject RG noticed that upon first wearing the rotation gear color constancy went “out the window.” To take one example, in normal conditions RG’s office during the day is brightly lit enough that turning on the fluorescent light makes no noticeable difference to the appearance of anything in the office. But when he turned the lights on after first donning the gear, everything had an immediate significant change of hue (though not brightness). He spent several minutes flipping the light on and off in amazement. Another example is that he also noticed that when holding a colored wooden block, the surfaces changed their apparent color quite noticeably as he moved it and rotated it, as if the surfaces were actively altering their color like a chameleon. This was also a source of prolonged amusement. However, after a few days the effect disappeared. Turning the office light on had little noticeable effect on the color of anything in his office, and the surfaces of objects resumed their usual boring constancy as illumination conditions or angles altered.” Interestingly the subject who wore the gear only part of each day never lost his normal colour consistency as he adapted to the other consistency; but the subject who wore the gear all the time had to re-adapt when he took off the gear although it took much less time than the adaption when the gear was first put on. I have often wonder how difficult it would be to lose this correction and for a while used a funny prism child’s toy to look at the uncorrected color of various shadows.

Did an adaption happen to bring the colours back to there original colours? Did the blue tomatoes start to look more red? It seems not, at least in this study. But again there were some interesting events.

On two occasions late into his six-day period of wearing the gear, JK went into a sudden panic because he thought that the rotation equipment was malfunctioning and no longer rotating his visual input. Both times, as he reports it, he suddenly had the impression that everything was looking normal. This caused panic because if there was a glitch causing the equipment to no longer rotate his visual input, then the experimental protocol would be compromised. …However, the equipment was not malfunctioning on either occasion, a fact of which JK quickly convinced himself both times by explicitly reflecting on the colors that objects, specifically his hands, appeared to have: “OK, my hand looks purplish, and purple is what it should like under rotation, so the equipment is still working correctly.”…the lack of a sense of novelty of strangeness made him briefly fear … He described it as a cessation of a “this is weird” signal.

Before and after the colour adaption period, they tested the memory-colour effect. This is done by adjusting the colour of an object until it appears a neutral grey. If the object always has a particular colour (bananas are yellow) then people over correct and move the colour past the neutral grey point. “One possible explanation of this effect is that when the image actually is grey scale, subjects’ top-down expectations about the usual color make it appear (in some way or another) to be slightly tinted in that hue. So when the image of the banana is actually completely grey scale subjects judge it to be slightly yellow. The actual color of the image must be slightly in the direction opposite yellow (periwinkle) in order to cancel this top- down effect and make the image appear grey. This is the memory-color effect.” This effect was slightly reduced after the experiment – as if bananas were not expected to be as yellow as they had been before the experiment.

They also looked at other aspects of adaption. “As we found, aesthetic judgments had started to adapt, … And though we did not find evidence of semantic adaptation, it would be quite surprising, given humans’ ability to learn new languages and dialects, if after a more extended period of time semantic adaptation did not occur.” They do not have clear evidence to say anything about qualia verses enactive adaptation but further similar experiments may give good evidence.

Misjudging criteria

Most people think of memory as the ‘past’ and judge it by how well it preserves the past. But that is not its function. Memory is material to be used in the ‘present’ and the ‘future’. What happened in the past is not important except to help understand the present and predict/plan the future. Bits of memory out of historical context are the ingredients of imagination. With more context they are the tools we use to identify things in the present and understand their dangers and opportunities. We need to know if we are encountering the old or the new. We need to remember whether someone is trustworthy when we deal with them. When we look at what we remember, how and how long we remember it, and how closely we keep it to the original memory, we should think of what is the point of all of it.

What seems a fault with memory – that memories are not fixed but can change or be lost altogether – is only a side effect of their being modified to stay relevant and useful. We need memories that help us perceive the present and model the future and that is the real criteria, not absolute accuracy. The criteria for a well constructed memory system are biological evolutionary survival ones.

Colour vision is not about accurately perceiving the frequencies of light coming into the eye. It is not about the light; it is about the surface that reflected the light and how it can be identified. There is no use in saying that our vision is not giving us accurate colour, because accurate colour would interfere with accurate characterization of surfaces and identification of objects. The many optical illusions are not faults in the system – they are due to the ways that the visual system protects the stability of our vision so that things do not appear to change colour or size.

Language is not about meaning or logic; it is about communication. People worry about changes in the meaning of words and the use of grammatical forms. Well, here is what happens generation after generation: if people have difficulty communicating, they will change their language. If their way of life changes, if they move to a different region, if the people they are talking to change, then they will change their language. Our language is not the result of biological evolution so much as cultural evolution. But the same idea applies and the criteria have to do with communication. Is language logical? It may seem so from within that language but talk to anyone learning it as a new language and see the illogical, arbitrary quirks in it. There are languages that count negatives and there must be an odd number to be negative. There are languages that have to have all or no words carry a negative marking. Both types of negation seem logical to the speakers. Is language a good communication tool? Without doubt it is better than anything else we have ever tried to invent. No artificial language has ever made a dent on a natural language no matter how clear was the meaning or logical the grammar of the new language.

When we look at biological and even social systems it is important to consider what is their real, primary reason for existence. We have a tendency to misjudge the criteria and need to watch out for this trap.

 

 

Colour words

It is well known that all languages do not have words for what we would call the basic colours of the rainbow – red, orange, yellow, green, blue, purple – along with white and black. Why can this be so?

First we can get rid of the idea that because they have no word for a colour, they cannot see it? Of course they can see it, they simply have no category that for that particular colour. Take a language without a word for blue: we would call a darker blue a shade of black and a lighter blue as a shade of white. To wonder why we would answer this way is like wondering why someone calls both straw and apricot shades of yellow. It is not that they cannot see the difference but that they have not formed those particular categories (because they have never spent hours picking the colours of paints, for example). How many colour names we have and the exact lines of demarcation between them depend on the culture/language we live in. When we see a colour in front of us, we see the visual perception and not the category/word/concept of a particular colour. We can compare two shades in front of us and say whether they are the same or different even if we only have one colour word for both of them.

Seeing is one thing but saying is another. All words are categories or concepts and encompass a good deal of variation. In the ‘space-landscape’ of colour, words are like large countries. As children we learn the geography of this space and the borders of each word’s domain. When we are asked to name a colour, we use the word that is the colour’s best category. We sort of understand where in the landscape that colour is and therefore which country it is in. To communicate we need to more of less agree on the borders of the categories and the word of each – otherwise that is no communication. If you say it is a red flower, I will imagine an archetypal flower with an average red colour.

Our culture does more than that. Culture can make connections between objects and colours. Some objects get defined by their colour. What colour is the sky? It is blue. It is a well known fact that the sky is blue. But the sky is not always blue – black on a dark night, various shades of grey (from almost white to quite dark grey with clouds), pink in the dawn, orange and red in the sunset, green with northern lights. Water is also blue by agreement although it is often grey, green, brown, yellow or red. If I think of leaf, green comes along. If I think of lemon, I also bring up yellow. The sky and blue is one of these conventional pairings. But where the colour is important it (in a sense) splits the object concept. It matters whether a wine is red or white, a chess-piece is black or white. The culture will force the noticing of colour when it is important in that culture. Quite often colours are identified by an object (like the apricot and straw mentioned above). This has been going on for a long time: orange from a Persian word for the fruit, yellow from a West German for gold, green from an old Germanic word of new growth, purple from the Greek for a mollusc that gave the royal dye.

Languages acquire colour words over time. Berlin and Kay examined the history of 110 languages and found that words for colour started with light and dark (not just white and black), followed by red (sometimes used as bright coloured), then green and yellow (sometimes together and then separating), then blue. Other colours where added later brown and orange (together sometimes at first), purple, pink, grey. Then we have many, many subcategories (sky blue, pea green) and border ones (aquamarine/turquoise at the green-blue border). I notice that lately when people list basic colours, they include pink along with the primary colours. This is new and implies that red has split to be red and pink. People do not want to call a pink thing red.

Unless it is very important, it seems that colour can be omitted from a memory. It is surprising how little we remember the colour of things. We can see things every day and not be able to remember their colour. There sometimes is simply no reason to remember.

We cannot know what people experience from looking at the words they have. The ancient Greeks lacked many colour words. But the idea that, “It seemed the Greeks lived in a murky and muddy world, devoid of color, mostly black and white and metallic, with occasional flashes of red or yellow”, is just wrong. Their poetry is not full of colourful images but that does not mean that their live was devoid of colour.