A saccade is a rapid eye movement (a jump) which is usually conjugate (i.e. both eyes move together in the same direction) and under voluntary control. Broadly speaking the purpose of these movements is to bring images of particular areas of the visual world to fall onto the fovea. Saccades are therefore a major instrument of selective visual attention. It is often convenient (but somewhat inaccurate) to consider both that a saccadic eye movement always occurs in a straight line and also that we do not ‘see’ during these movements. We can therefore simply consider that we often see the world by means of a series of saccadic jumps from one area to another, interspersed with fixations. Note, however, that these are oversimplifications.