Do you see what I see? Probably not…

In my day job I’m an academic psychologist, and one of my favourite areas to teach is perception – how we experience the world around us. It’s endlessly interesting and intriguing, mostly because our brains are cooking up reality for us – what you see is literally a construct of your brain.

Take colour for instance, there is no such thing as colour. Yes, I’m being serious. We have cells in our eyes which are receptive to light waves and can translate them into the electrical signals our brain likes. Our brains then interpret those light waves as colour.

Take this lemon….there is not a single bit of yellow on it. Really.

lemonhttp://www.iflscience.com/editors-blog/not-yellow

Anybody confused yet?!

Are you old enough to remember the old TV sets (the really old, analogue ones with the push buttons and dials!)? Did you look up closely at the TV at all (probably), what you saw was 3 pixels in a little triangle shape, and they were red, blue and green. We couldn’t work out how those 3 colours made all the different colours on screen.

The only thing that has changed was the size of the pixels (they’re now really tiny and called megapixels) – they mimic our light spectrum. There are 3 wavelengths of light – red, green and blue. Those 3 wavelengths of light create our entire colour spectrum. And they’re not even technically red, green and blue, they’re 420nm (blue), 530nm (green), 560 (yellow-green – aka red, yes really).

Actually, there’s technically no such thing as colour. I’m serious, it’s all light at different wavelengths, it’s only processed in a manner that means it can be interpreted as colour because we have evolved cells which translate this light into a signal the brain can recognise. Then we labelled the experience of those signals.

Think of left and right, they’re arbitrary labels even though most of us know which direction them mean instinctively. We learn what the labels are. Colour is the same, we’ve learned what the experience of particular light waves are called because others have taught us – we have learned colour. Really.

When the images of ‘that dress’ hit last year, it was a gift for perceptual scientists, we knew what was happening very quickly, and everyone instantly added it to lectures and talks. It’s a brilliant example of how what we see is influenced by experience.

Contrary to what most of you think, we can’t trust what we see anything like as much as we might like – in fact what we see is a construct of our brain. Yes, our brain is literally cooking up what we see – and this is all based on what we have already experienced. What you experience influences how you see the world around you.

Take this video of girls dancing that went viral a year or so ago – working out whose leg belongs to whom is surprisingly quite tricky, the visual cues keep changing and so as soon as you stabilise the ‘correct’ interpretation they change the dance move and your brain is all scrambled again. The reason we can’t see it correctly for very long is because of something called the law of similarity from the Gestalt School of Psychology.

black and white dancershttp://www.youtube.com/watch?v=44mw37d8LQw

Things that are similar are grouped together by our brains, whether they actually go together or not. It’s how we are able to see objects at strange angles and with parts of them obscured. We see the separate elements as similar so we mentally group them together.

So back to the dress. Here it is:

the dressIs the dress blue and black or is the dress white and gold?

I see it as white and gold….and that will instantly confuse all of you who see it as blue and black. The rest of you are wondering how on earth anyone can be confused by it – clearly gold and white, right?

What those who see it as white and gold were/will be initially a little freaked out about is that the original dress IS blue and black. So…what is the explanation?

There were lots of explanations which went around at the time, sadly many were in techy/science speak and while they did a great job explaining the effect, you needed to have a science background to understand properly. So…for those who pursued other topics of education, I’ll try and phrase it a bit more simply…here we go…

Light hits objects in the world and our eyes interpret these light signals. We have things called cone cells in our eyes – they are on the retina (the bit at the back of the eye that all the light hits) – and have a protein in them called opsin, and it’s this opsin which starts off the translation process of light waves into electrical signals.

pair of eyesSo the light signal is turned into electrical signals which are then interpreted by the brain. This interpretation is based on what we already know about our world – what we’ve seen before, in other words our experiences. Our brains create shortcuts for interpreting light (and everything) because to process everything start to finish every time we see something would require a brain like Marvin the Paranoid Android from Hitchhiker’s Guide to the Galaxy – ‘a brain the size of the universe’. So we create shortcuts, it’s much easier.

marvinNow, there are different amounts of light in different situations (inside/outside is the critical difference for this example). Our brains are designed to account for different levels of lighting, the luminance, and work on the actual amount of light bouncing off the objects in relation to the light around. This means we can see objects as consistent colours whatever changes to the amount or type of light in the environment. So, your blue jumper is always that particular colour of blue whether you’re inside or outside.

Still with me?

Usually this system works fine, we are able to see things consistently with no problem. However, this image of the dress hits what is known as a perceptual boundary. Our brains are hardwired to account for the fact that daylight changes colours slightly, we have evolved with daylight and so our brains can cope with this just fine.

The light colour is important now – daylight is blue/white during the day. Your brain discounts the blue it normally sees, it filters it out so you do not see the world with a hint of blue. Artificial light has a yellow tinge (can you see where I’m going yet?), and we might not have evolved much with artificial light, but we have grown up with it. So your brain is also able to filter out the yellow tinge that everything would otherwise have.

Daylight on the right, artifical light on the left.

Daylight on the right, artifical light on the left.

So your brain filters out the blue in daylight and filters out the yellow in artificial light.

How you see the dress depends on how you interpret where the light in the background is coming from.

*If you see the background as daylight, then you see the dress as gold/white because you’ve filtered out the blue.

*If you see the background as artificial light then you will have filtered out the yellow and will see it as blue/black.

There we go, hope you stayed with me to the end.

There are other examples of this phenomena – this girl’s hair went viral on social networks too, as it went from pink to purple depending on the light it was exposed to, and therefore how it was interpreted by the viewer. It’s the same principle, but it’s not quite as mysterious as the Daily Fail seem to think.

purple pink hairhttp://www.dailymail.co.uk/femail/article-3103225/Video-clip-showing-girl-s-hair-mysteriously-change-purple-pink-walks-house-taken-internet-storm.html

A basic image that can also be used is this one, the standard cubes.

cubesAre the two faces of the cube different shades of grey?

They’re the same shade and they’re interpreted as being different shades because of the backgrounds they’re on – the amount of light that is reflected relative to the background is different. A slightly different variation of this phenomena from the dress but still the same principle. There is a perceptual boundary where knowledge overrides what is actually being seen.

This is my favourite bit of perception – this perceptual boundary when what we know completely overrules what is actually in front of us.

Vx

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