The grand illusion

Abstract

We may have powerful intuitions about our own minds, but they must be questioned. Could vision, consciousness, self, and free will all be illusory – meaning that they are not what they seem? This chapter concentrates on whether vision is a ‘grand illusion’. This idea emerged from research on ‘change blindness’, which found that even large changes in an image can go unnoticed if made when the image is moved (to force an eye movement) or a brief flash is inserted (to mimic a blink). In ‘inattentional blindness’, people can miss events they are looking directly at if they are not paying attention. Magicians have long used these effects to trick people. The vexed question of ‘filling-in’ arises when part of an object is obscured by another or when part of the scene falls on our blind spot. Does the brain ‘fill in’ the missing details? Does it need to? Evidence pointing both ways is reviewed and opposing theories are considered, including enactivist and sensorimotor theories, which treat seeing as a form of action. These ideas and discoveries all challenge the intuitive idea that visual consciousness involves building up a rich picture of the world inside our heads.