It has become a truism that the frozen optical diagram representation of vision is the worst possible picture of the way in which we visually interact with the environment. Even apart from our reaction to moving targets by pursuit movements, our visual behaviour can be said to be characterised by eye movements. We sample from our environment in a series of relatively brief fixations which move from one point to another in a series of extremely rapid jerks known as saccades. Many questions arising from this characteristic of vision are explored within this volume, including the question of how...