We rely on our eyes for almost everything we do. In fact, 50% of the brain’s cortex is devoted to vision alone. But our eyes cannot always be relied upon to tell us the truth. Visual, or optical, illusions challenge our minds to interpret distorted information so that it makes sense to us. Thus, what you think you see is often just an assumption rather than reality.
The power of illusion was recognised as far back as ancient Greek times when philosopher Aristotle witnessed motion aftereffect. Whilst looking at a waterfall, he switched his gaze to some rocks and found that the rocks appeared to move in the opposite direction to the flow of water. In his words, “our senses can be trusted, but they can be easily fooled.” But it’s not just motion that can warp our perception of the world around us. The 19th century saw a real boom in the study of illusions. Scientists were keen to discover how patterns and shapes, and even colour, might be interpreted by the brain in certain situations, and created simple visual illusions to get their answers. Well-known examples include the Ebbinghaus illusion, where the brain is found to make judgements on the size of an object by comparing it to adjacent objects. And the Muller-Lyer illusion, where arrows placed at either end of three lines trick the brain into thinking the lines are different lengths when, in fact, they’re all the same.
Fast forward to today, and optical illusions are all around us. They’re even a recognised art form. Advances in science and technology have offered more explanations as to why our brains process certain visual information the way they do, but they are not yet able to decipher all illusions. Perhaps our visual system is simply too limited to tackle all of the information it is presented with? Perhaps it is down to evolution to provide the answers we seek?
Infographic courtesy of Cartridge People.