By Veronica Wignall, Society of Biology volunteer
Recently a picture of a dress divided the world in an unprecedented debate about its colour: was it white or gold, or blue and black? The neuroscience of visual illusions has been thrown into the spotlight, revealing the tricks our brains play on us – and how they help us to survive.
Which way does the ballerina (below) spin?
Can you make her change direction?
The spinning ballerina test is just one of a myriad of optical illusions, and there is even an Illusion of the Year contest. These provide interesting insights into how our brain stretches visual truths to make the world make sense.
What we might not realise is just how often our brain is dealing with visual illusions, modulating our perception so that we aren’t befuddled by tricks of the light.
When we see a piece of white paper, we know it is white whether we are outside under a blue sky or indoors under infra-red lighting. This is because our brain unconsciously corrects for the colour of the illuminant, or light source. It is this concept that caused the rift in the #dressgate dilemma, neatly explained in New Scientist.
When things are missing, the brain fills them in using surrounding information to complete the picture. That’s why we don’t constantly have a gap in our vision where our blind spot, or scotoma, obscures our visual field. The simple blind spot test shows how important this is.
In the famous Kanizsa Triangle, our brain extrapolates a simple diagram into a 3D image in which a bright white triangle is laid over three black circles, an effect known as an ‘illusory contour’. This works in colour, too.
Our visual perception can even influence our psychology. Colour psychology is regularly used in advertisement and branding. Certain colours are used to make you hungry, while others to give an impression of authority.
Our brains are constantly compensating to make the world a coherent place, filling in the gaps to help us get by. Optical illusions can demonstrate perfectly how we see with our brains, rather than our eyes, a subject that Professor Bruce Hood FSB will canvass during his talk.