Colour - do you see what I see?

Notes on a Horizon Documentary, BBC 2, 8 August 2011

Do we see colour as others do? Yes and no.

• Light exists in the physical world. However, despite appearances, colour does not.
• Rather colour is perception. Perception is personal. 
• We create colour from light according to our past experience. 
• Our past experience is a learned response. I
• t is partly personal, and so unique, and partly cultural, and so common to the society in which we are embedded.

In its raw state the image of what we see on the retina is an ambiguous pattern of light. It is also upside down. Our brain must make sense of this data for us to function. Our brain searches for patterns that it found useful in the past. Using that information, it shapes our response.

To show that colour is perception based on past experience, first look at the two desert scenes below. The colours in each are the same. Now stare at the dot between the red and green squares for at least 60 seconds. Then look back at the dot between the two desert scenes. For most people, the clouds in the left-hand image will turn pink, whilst those on the right will turn green. This occurs because, stimulated by the recent memory of red on the left and green on the right, our brains overlays this memory onto our immediate perception of the desert scenes, at least for a while.

To see the influence of culture on the perception of colour, Dr Beau Lotte, in an experiment undertaken for this documentary, asked a group of 150 British people of different ages, backgrounds, races and sex to associate emotion with colours. He discovered that nearly every adult assigned yellow to happiness, blue to sadness and red to anger (surprise and fear, which are the other two universal emotions, had no obvious colour). While children showed the same trend, their choices were far more mixed and variable.

In another experiment he asked people to put 49 coloured blocks on a surface area of 49 spaces. They had no other instruction. Whilst billions of different combinations of colours were possible, people in the study made patterns that were largely predictable. Most grouped colours in a similar way. Why? Human have an inherent need for structure. Our ordering of colour is no different. Here we often repeat the patterns of colour which we see in our environment to select and combine colour. Sharing the same environment leads to shared perceptions.

One important variation in culture is language. Western languages usually categorise colours into 11 basic categories: red, orange, yellow, green, blue, indigo, violet, pink, brown, black, white and grey. However, in cultures with fewer categories of colour definition, people’s perception of colour differs significantly from our broadly shared western view.