What do we study when we use eye tracking data?

Most eye tracking studies aim to identify and analyze patterns of visual attention of individuals as they perform specific tasks (e.g. reading, searching, scanning an image, driving, etc.). In these studies eye movements are typically analyzed in terms of fixations and saccades. During each saccade visual acuity is suppressed and, as a result, we are unable to see at all. We perceive the world visually only through fixations. The brain virtually integrates the visual images that we acquire through successive fixations into a visual scene or object. Furthermore, we can only combine features into an accurate perception when we fixate and focus our attention on them. The more complicated, confusing or interesting those features are the longer we need to process them and, consequently, more time is spent fixating on them. In most cases we can only perceive and interpret something clearly when we fixate on an object or are very close to it. This eye-mind relationship is what makes it possible to use eye movement measurements to tell us something about human behavior.