Fixation (visual)

Fixation or visual fixation is the maintaining of the visual gaze on a location. Humans (and other animals with a fovea) typically alternate saccades and visual fixations, the notable exception being in smooth pursuit, controlled by a different set of ocularmotor muscles that appear to have developed for hunting prey.

Reading involves fixating on a successive locations across the page or screen. Visual fixation is never perfectly steady: fixational eye movements occur involuntarily. The term "fixation" can also be used to refer to the point in time and space of focus rather than to the act of fixating; a fixation in this sense is the point between any two saccades, during which the eyes are relatively stationary and virtually all visual input occurs (e.g., Martin 1974).

Fixation is also used in experiments in vision science or neuroscience. Human subjects are often told to fixate on an object on a monitor before any experiment takes place. This serves to direct the person's attention to the point where visual information will be presented. In experiments involving tracking eye movements, fixation serves as a starting point for all subsequent eye movements.