HOW OPTICAL ILLUSIONS WORK
WHY DO OUR EYES PLAY TRICKS ON OUR BRAIN?
Some people say that seeing is believing. We expect what we see to exist. When we look at what’s in front of our eyes, each scene comes with masses of information. What do the shapes mean and how do they connect? To make sense of the world around us, we rely on our eyes to provide our brains with accurate visual information – but sometimes our eyes can deceive us. Optical illusions make you see things which aren’t physically there, give motion to shapes that are static and can even make something impossible seem real. Split into three main categories – literal, physiological and cognitive – each has a distinctive way of producing these mystical marvels. Not merely entertaining out-ofthe-ordinary spectacles, visual illusions provide insight into the vital science behind eye-brain interactions. For many of these visual wonders, you need to approach them with some existing knowledge. Take the title of this article as an example. You would have known immediately that you were reading about optical illusions. But how? Illusions can be incorporated into text as well as images. To someone unfamiliar with the shape of letters or the English alphabet, these blocks and shapes would hold no other meaning. For your brain to receive the information, it analysed the shapes and compared them to the knowledge stored in your memory, reading the shapes as letters. Focusing your attention solely on the blocks themselves would leave you with a meaningless pattern. The following illusions will put your eyes and brain to the test. What will your brain be able to comprehend and how will your eyes throw it off track?
Hidden faces
Deception isn’t always carefully planned. Sometimes nature and the everyday muddle your brain too. Nature’s unique shapes and forms can cause you to find new and unusual variations around every unexplored corner. Within the bark of this tree, the growths and dents reveal an imposter. Immediately your eyes are drawn to the shape of a face at the centre, highlighted by the light covering of moss. Your brain is familiar with the form of a human face, as you are likely to see many of them as you go about each day. When presented with this tree, while it is only a tree and not literally a face, your brain recognises both, and it will struggle not to see this familiar fat-lipped figure every time you glance back.