What Is Colour?
To understand why some people do not learn what colours are, it is helpful to learn what colour is, beyond the obvious differences in colour of the things in front of us that we take for granted.
Some describe colour as wavelength of light (explained in lesson 3c) - this is one way of thinking of colour, but this does not explain the sensation of colour.
Let us use the example of a carrot.
A carrot is real, you can feel it, and you can eat it, but to understand the idea of colour we need to separate the object that is the carrot, from the colour that we see.
Can you experience a carrot without it being orange?
Try picking a carrot up with your eyes closed, You can feel it, and smell it, but you have to open your eyes to experience its colour.
As explained in Level 1, the only way you can experience the carrot, not just what it looks like but also what it feels like and tastes like, is through your brain.
All 'incoming' information you receive through your senses is experienced in your brain.
For vision, the brain re-creates what you are looking at as a picture in your mind that matches what you are seeing.
The carrot is only orange when you look at it. Close your eyes... you can still feel the carrot, but the colour has gone.
Only your eyes can receive colour and send this information to be processed in your brain.
So what is colour? What is the orange of the carrot? Colour has no form, it has no matter, it has no taste nor smell.
The orange colour of the carrot is completely abstract.
Here's the problem with colour and CVI. For those who don't see things typically, and can't search for things typically, and don't have an age typical understanding of shapes and objects, especially if the CVI has been present since birth, then it does not follow that they will naturally pick up what colours are. They might be able to see them, but they may not always understand what people mean when they talk about colours, by the names of the colours. So they may need to be taught about what colours are in a way they can learn from.
Colour blindness is rarely a cerebral visual impairment (case description at end of page if interested).
Usually though, with colour blindness, certain colours are not processed typically by the eyes, so that some colours are not seen.
The most common form of colour blindness is red / green colour blindness, although there are other combinations.
Around 8% of men but less than 1% of women are colour blind.
If a person appears to not see or recognise colours, it is important to find out whether colour blindness is the cause.
For more information on colour blindness there are many on-line resources, tests and simulators, and your local optometrist can provide further support.
Colours are abstract, but most people quickly learn the names of colours at a young age. For children with CVI, learning can be more difficult for many different reasons.
Consider a simple instruction like, 'pass me the blue cup please'
This requires the child to know:
This knowledge may seem so basic, that it is not explained. It is just assumed the child knows what blue and a cup shape is (and can see as other children do, to look for things).
When the child is unable to find blue things, it may be thought that they can't see blue. Unless the person is colour blind, it is possible but unlikely that they are unable to see the colour, and much more likely that they do not know the colour, because they have yet to learnt what its name is.
Teaching children colour names is relatively straight forward, even for children who do not speak and have complex disabilities, but many approach it the wrong way around. What is this...
If your answer is 'A BLUE CAR' then you are of course correct, but this is why some children do not learn colours.
What is blue? (see What is Colour? above)
To teach colours, it is important to start with the something that is already known, like a car, or maybe the sky, and to begin, say 'car blue' (starting with the known car, then adding the colour blue) rather than blue car. Or sky blue rather then blue sky.
CVI Scotland has developed free computer games (called COOL) to help teach both the concept of colour and colour names.
Some think that children with CVI can see certain colours better than others, particularly reds, yellows and oranges. There is no evidence that any colours are more visible than others, but some do have colour preferences. Colour preferences occur where there is a significant attachment to a colour, and this could be for positive reasons, for example a regular colour worn by a loved person, or negative reasons, like the colour of a toy that makes a lot of noise and is scary.
Contrast, as explained in the previous lesson (Lesson 5c) is key, and a more reflective colour like yellow will be more visible against a background with low reflection like black, but less visible against a highly reflective background like white.
Colours should be clearly named while the child is learning to name colours, in connection with something already known. This is the case whether the child is profoundly disabled or very able.
A favourite toy for example...
Elmo is red.
If difficulties with colour naming are the cause of recognition or learning challenges, this needs to be found out. The simple exercise of asking a person to name the colours of different items can help build up a picture of which colour names are not known.
When a colour's name is not recognised, it can look like something of that colour can't be seen or understood.
Going back to our example, 'Please pass the blue cup' - what would your thoughts be if the child either couldn't do it, refused to do it, or brought you back a different coloured cup or a random object?
Would a lack of ability to understand the concept of colour occur to you, as the reason for not passing you the blue cup, when asked?
Look around you, try to imagine not knowing what colours are? It is almost impossible to imagine what it might be like to not know the names of colours. When describing things or giving directions, we often use colour, assuming both the person sees as we do, and understands as we do. But not everyone does.
Do not assume everyone is able to name and recognise colours as you do, particularly those with CVI.
Little is known about impairment or lack of colour vision brought about by injury to the area V4 of the brain. V4 is part of the occipital lobes (lesson 1b) and serves colour vision. Where there is a partial or total absence of colour vision due to brain injury this is called cerebral achromatopsia, while impairment of colour vision due to brain injury is called cerebral dyschromatopsia. If the condition has been present since birth, it may be difficult to recognise and assess, but will cause difficulties with object recognition and naming colours. Research has found difficulties with colour vision in adults who have suffered cerebral hypoxia from reduced oxygen flow to the brain, called cerebral hypoxia. (For example due to carbon monoxide poisoning). Cerebral hypoxia is one of the most common causes of CVI in children and is an area we believe needs further research to find out whether and how colour vision is affected.
Before you move on to the next lesson, please check you have understood:
Next Lesson Level 6a CVIs Visual Field Impairments - Hemianopia
Further reading is not necessary to move on to the next level, but if interested you may enjoy the following:
COOL (free Colour Concept and Naming Tool):
What Is CVI? - The Image / Colour
CVI Autism Team Blog 1 - explains two boys' strong colour preferences and the causes. One boy loved blue, the other boy's love of purple became an obsession.
There are many on-line resources explaining in more detail how the human eye processes colour.
Case of CVI causing colour blindness.
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