What You See is Not Always What it SeemsPerhaps the most complex mechanism in your body is your ability to see. However, this also means that errors regularly appear in the process of seeing, although we might never actually notice. Did you know, for example, that when you see, the image displayed in your eyes is upside down? It is your brain that turns everything right-side-up, because it is much easier to navigate in a right-side-up world. If you were to wear a set of contact lenses that turns everything upside down, your brain would automatically turn it right-side-up again after a few days. In truth then, all you see is the result of your brain’s subconscious operation. Your brain constantly attempts to correct images so they look how the brain expects them to look. In fact, this is also how we perceive the world in three dimensions. The image that is displayed on your retina inside your eye is a two-dimensional one, but the brain sees depth and distance. This is apparent in the Ponzo illusion above, where the distance cues provided by the wall tricks our brain to think that the line that is “further away” should be bigger. In the same way, your brain will also adjust colours, for example in accordance with shadows. In the Adelson illusion below, tile A and tile B are the exact same colour. Even when you know this fact, it is nearly impossible to see. No one knows exactly why, but the shadow of the cylinder and the pattern of the surrounding tiles tricks the brain into thinking that tile B must be another colour than tile A.
Sometimes, your brain’s subconscious alterations can result in quite a mess. Take a look at the café wall illusion below, named so after it was discovered by a scientist at a local café. All the horizontal lines are parallel, but your brain is so busy trying to distinct the white squares from the black squares that the horizontal lines are skewed in the process.
Your Brain Assesses Importance and Prioritizes Everything You SenseAnother subliminal process that eludes us all is the brain’s prioritization of importance. Whenever we use our senses, our brains will assess which part of the sensory impression is most important and guide our focus toward it. For example, try reading the following words.
GREEN – RED – ORANGE – RED – PURPLE – GREEN – YELLOW – RED –BLUE – PURPLE – GREEN – REDNow try saying the colours of the words. You will find that it is much harder to say the colours of the words as opposed to just reading them. This is because we do not usually have to pay attention to the colour of words. For that reason, our brains will instinctively rate the meaning of the word as more important than the colour of the word. When we then have to pay attention to the colour of the word, we have to bypass the brain’s prioritization, which is not such an easy thing to do.
In order to understand how often this prioritization of sensory impressions affects us, we can take a look at the Kanisza triangle below. We can all clearly see a white triangle that has its tips inside the black circles, even though the triangle is not actually outlined. However, because our brain is used to seeing full shapes, what we see instinctively is an image of a white triangle on top of another triangle and three circles. Now try to convince yourself that the image is simply three Pacman-shapes and three V-shapes. This simple task is very difficult because our brains keep constructing the white triangle.