sentences:  Eye trackers bounce near infrared light off the interior of the eyeball, and monitor the reflection on the eye to determine gaze location.With this technique, the position of a fixation on a screen can be precisely determined.Wang (2011) mentioned that a video-based eye-tracker which uses video cameras to record the eye position of human subjects—recording pupil dilation and eye movement—can be used to examine how fixations, saccades, and pupil dilation responses are related to the information on the screen and behavioral choices.