Features Columnist Catherine Heffner takes us down the bright route of colour perception and how the brain works in her latest article.
THIS IS YELLOW.
Or is it? Would it blow your mind if I told you that the colour you’re looking at is actually a fake?
“Real” yellow is what is known as a subtractive colour. Yellow things appear yellow because they absorb all other colours in the spectrum except for certain wavelengths, which are reflected into your retinas and interpreted by your brain as yellow. Well, this being Exeposé Online, I can safely assume you’re reading this on a screen of some sort. But the screen you’re using isn’t emitting any yellow light at all – a screen is purely made up of red, green and blue elements. So how is your brain so easily deceived?
Since yellow falls between red and green on the colour spectrum, your brain perceives yellow by an activation of cells in the eye for both red and green. All your screen has to do is emit the right amount of red and green wavelengths to create a sort of virtual yellow.
Colour can be described as an illusion. Unlike properties of the universe such as gravity, colours are created and interpreted in our own minds. Our brains are able to interpret a certain range of the electromagnetic spectrum into what we know as colour. And it’s impossible to know whether the colours you see appear the same to you as they do to me. Some tests for colour blindness show us that many people experience colours in different ways. In Britain, a staggering 4.5 per cent of the population are colour blind, ranging from those lacking the ability to fully recognise certain colours to those who cannot see any colour at all (monochromatic vision).
These diagnoses come from the results of the colour blindness tests that have been developed over time. But how do we know that there aren’t other differences in the way we perceive colour that cannot be defined by existing tests? How do I know that the blue you see is the same blue that I see? Private, subjective, conscious phenomena such as these are referred to as “qualia”. They also include other sensory experiences such as pain, taste and sound. Philosophers have debated whether the issue of qualia is down to an explanatory gap. Daniel Dennett notes that the difficulty of describing the concept of a fully colourful world to a blind or colour blind person could be down to a failure of our language, rather than a failure of the blind or colour blind person’s understanding.
But colour doesn’t necessarily have to be perceived in one way. Some people have a neurological experience known as synaesthesia whereby stimulation of one sensory pathway initiates stimulation of a second sensory pathway. For instance, people with synaesthesia might associate letters or numbers with particular colours. Neuroimaging studies have identified differences in patterns of their brain activation.
Those of us without synaesthesia can still experience a similar perception of colour. There’s a great video on YouTube by minutephysics that actually shows you the sound of hydrogen. Yep, that’s right – you can hear it. Or at least, you can hear a representation of what hydrogen would sound like if it emitted sound waves instead of light waves, and if the sound was pitch-shifted into the audible human range.
This same concept of turning colour into sound was taken on by artist Neil Harbisson to tnsform himself into what he describes as a human cyborg. Born with achromatopsia (total colour blindness), Harbisson enlisted the help of computer scientists to design an electronic “eye” to allow him to hear colour.
The “eye” he wears is basically a colour sensor that detects colour frequencies from his surroundings and transmits them in the form of sound waves to a chip in the back of his head, which he is able to hear via bone conduction. Initially, Harbisson had to memorize the notes of each colour, but over the eight years he has spent wearing this device, he was able to develop this process into one of perception.
Now he intuitively knows the sound of any given colour. Not only can he effortlessly perceive all degrees of colour in the colour wheel, but he has also extended his perception to colours outside of the visible spectrum for humans such as infrared and UV light. At the point where he began to dream in colour, he realised that the electronics he wears and his brain had become united. He now views the eye as an extension of his mind, and describes himself as a cyborg. Harbisson has since founded the Cyborg Foundation which aims to encourage the development of humans into cyborgs and protect their rights in society.
While we can think of colour as a purely subjective experience, there’s no denying it as a property of the universe.Thanks to today’s telescopes, we’ve all seen those incredible pictures of stars and galaxies and nebulae in wonderfully ethereal looking colours. Well, believe it or not, those colours can actually tell us about the characteristics of space itself. Blue, for instance, indicates a region with many young stars.
Young stars burn very fast, causing them to emit high temperature radiation of a blue colour. A region of old stars, however, will appear red since the high-mass stars emit cooler radiation of a red colour. Looking at light wavelengths outside the visible range such as radio, infrared, UV, x-ray and gamma-ray can also give us more information about the characteristics of the galaxies*. In 2012, astronomers announced that they had determined the exact colour of the Milky Way. Unsurprisingly, the Milky Way is white. But the exact colour can give us a lot of information about our galaxy – how old the stars in our galaxy are, how recently stars have been forming. According to the colours found, the Milky Way is somewhere in between and the old and the new states of a galaxy, with the rate of new star formation declining over time.
Artist Josef Albers put it this way: “every perception of colour is an illusion…we do not see colours as they really are. In our perception they alter one another”. Looking at colours can show us how the line between our observable reality and our inner experience is a blurry one. It’s strange to think how our perceptions are so limited by our senses yet so utterly dependent on them.
* It is worth noting here that sometimes colours we see in astronomical images are not actually the colours we would see with our eyes but are representative of different wavelengths of light used to produce the image. Often images are taken in wavelengths not visible to the human eye, and so colours are used to provide a representation of the different wavelengths that we can’t see.
Catherine Heffner, Online Features Columnistbookmark me