Sunday, March 29, 2015

Blue and Black or White and Gold?

Would you like to have an argument with your colleagues this fine Friday? Just ask them what colour the dress above is. Some people say white and gold, whereas others claim it’s clearly blue and black. This rift in opinions has caused many people to doubt the sanity of themselves and their friends. Excitingly, it also offers some sort of insight into the famous old philosophical question: “is your red the same as my red?” But why are people so divided by this?
It appears to be because of different interpretations of how the scene is illuminated. The brain automatically “processes” visual input before we consciously perceive it. Differences in this processing between people may underlie The Great Dress Debate.
In our everyday lives, there are many changes in the colour of the light illuminating our surroundings. For example, the yellow glow of an incandescent light bulb versus the blue-ish hue of a fluorescent light. The light that an object reflects to the eye is a combination of both the colour of the object itself and the spectrum of the light source, which may vary. The brain is able to disentangle these two things and decide what colour the object is. Simply put, objects appear the same colour even if the light illuminating them changes – a concept known as colour constancy.
So, how does the brain keep colours constant? One way is by using reference points. For example, say you know your mug is white, but the light being reflected from the mug is slightly red. The brain can then discount a certain amount of red tint from the rest of the scene you are seeing. Other contextual knowledge may come into play, for example you are drinking coffee by the window at dawn. It makes sense for the light to be red-tinted as the illumination source is the sunrise. This is known as top-down processing. All of our perceptual experiences are informed by this kind of processing, resulting from context and previous knowledge.
This is possibly something you’ve never thought about or been aware of before - you may well underestimate just how much the lighting in our world changes, because your brain compensates for it so well. This happens automatically without any conscious awareness. But, colour constancy is not perfect. In The Dress photo, there aren’t many cues or reference points to tell us the properties of the light source. This leads to ambiguity and the possibility of different interpretations.
This image is a fascinating example of something on the edge of a perceptual boundary. Some people’s colour constancy is calibrated so that their brains tell them they are seeing gold and white, whereas some are lead to believe they see black and blue. Of course, the colour constancy mechanism is always learning, and due to top-down information (e.g. reading others’ opinions) this calibration could change and lead to another experience. This may be the driving force behind people experiencing a shift from seeing white and gold to blue and black.
Imagine how the world would look without colour constancy; objects would always be changing colour as you walked, say, through your house at different times of the day. I am currently doing research on the development of colour constancy in children within the Sussex Colour Group. Toddlers may experience a lower level of colour constancy than adults, making the world even more confusing for them. It has also been suggestedthat Monet was somehow able to disregard this automatic process in order to paint scenes showing how light progressed over the day. To most of us, the change in the colour of light over the day would be less noticeable.
There now appears to be good evidence that The Dress is in fact blue and black (but it’s always good to keep some scepticism regarding information on the internet). Therefore, arguably, people who originally saw it this way have better colour constancy. They were able to take cues from the background and compensate for the very unnatural illumination. There is evidence that people with good colour constancy also have better working memory (a part of short term memory dedicated to immediate perceptual processing) and that these two processes may be related.
Those who originally saw The Dress as blue and black should not be too smug, though. Some may argue that colour itself is just a construct imposed by the brain to make sense of the world. What enters the eye is just a spectrum of wavelengths of light, we turn that into something with category boundaries and labels and connotations. But one thing’s for certain; The Dress is a brilliant example of how breaking the perceptual system helps us to learn more about how our brains work.
~ The Guardian