What is Eye tracking?
Eye tracking is the field of monitoring what people do with their eyes – observing what people choose to look at, how their eyes move, how their visual activities behave. Eye trackers are the instruments that measure our eye behavior. They measure the directions that our eyes are pointed and predict our gaze points, i.e. the locations of the objects in space that we look at.
Many modern eye trackers are based on video cameras that observe our eyes and produce high-resolution images of our irises, pupils, and scleras. Light emitting diodes illuminate the eyes, and these LEDs produce reflections off the corneal surfaces to provide critical geometric information about the orientation of the eyeball.
Behind the cameras that capture the images of the eyes, an essential part of an eye tracker is the image processing function that identifies the eyes within the images, measures the geometric features of the eye elements, and computes the spatial positions and orientations of the eyes. Finally, eye trackers project the spatial locations of the eye’s gaze points. If a person is looking at a computer screen, for example, the gaze point may be expressed in x,y screen coordinates.
Significance of Eye Tracking
Our eyes and vision systems are our brain’s primary tools for gathering current information about our environment. They are the means through which we live the visual dimension of our life experience. At the same time, our eyes can only look one place at a time. Our brains have evolved a highly sophisticated strategy to point our eyes at what we predict will provide the most useful visual information available to us at the time.
With eye trackers researchers can observe what our brains choose to look at. While eyetracking instruments cannot explain why our brain chooses to look at specific things, they do measure and record the sequence of visual pointing decisions the brain ultimately makes. From eye tracking data we can make powerful inferences about what is visually important to people’s underlying cognitive processes.