Eye tracking
From Freepedia
Eye tracking is a technique used in cognitive science, psychology (notably psycholinguistics), human-computer interaction (HCI), advertising, medical research, and other areas. A camera focuses on one or both eyes and records their movement as the viewer looks at some kind of stimulus. Most modern eye-trackers use contrast to locate the center of the pupil and use infrared beams to create a corneal reflection, and the triangulation of both to deteremine the fixation point. However, eye tracking setups vary greatly; some are head-mounted, some require the head to be stable (for example, with a chin rest), and some automatically track the head as well. Most use a frequency of at least 30Hz in order to capture the detail of the very rapid eye movements.
Ocular movements are typically divided into fixations and saccades, when the eye gaze pauses in a certain position, and when it moves to another position, respectively. The resulting series of fixations and saccades is called a scanpath. Most information from the eye is made available during a fixation, but not during a saccade. The central one or two degrees of the visual angle (the fovea) provide the bulk of visual information; the input from larger eccentricities (the periphery) is less informative. Hence, the locations of fixations along a scanpath show what information loci on the stimulus were processed during an eye tracking session. Most people cannot make a conscious saccade in less than 200 milliseconds.
Scanpaths are useful for analyzing cognitive intent, interest, and salience. Other biological factors (some as simple as gender) may affect the scanpath as well. Eye tracking in HCI typically investigates the scanpath for usability purposes, or as a method of input in gaze-contingent displays or gaze-based interfaces.
References
Rayner, K. (1998) Eye movements in reading and information processing: 20 years of research. Psychological Bulletin, 124, 372-422.
Duchowski, A. T., "A Breadth-First Survey of Eye Tracking Applications", Behavior Research Methods, Instruments, & Computers (BRMIC), 34(4), November 2002, pp.455-470.
