It’s important to realise that the brain doesn't see the world around it simply as though the scene was projected onto a cinema screen on the inside of your skull. Before a scene can be observed "in your head" it has to be broken down into a number of different components for processing, and these components then have to be recombined into the meaningful form that we call "an image". Amongst other things, the scene is broken down into its different colours — red, green and blue — in a way that's analogous to the manner in which a television image or magazine photograph is broken down into tiny dots of primary colours (which are too small to be noticed individually when we look at them, but which when seen collectively give the impression of a continuous full colour image). However, unlike and magazine images, the image that we see with our eyes is broken down not only into separate colour components but into other components too. It is, rather incredibly, deconstructed into component parts such as horizontal lines, vertical lines, circles and so on. Each of these component parts is sent to a separate area of the brain for processing, with the different components of the scene only merging again when they are unified into what you perceive as the image.