Pupil Dilation and Eye-tracking

A video-based eye-tracker (e.g., the mobile Eyelink II or Eyelink Remote of SR research, Osgoode, Ontario, Canada) uses video cameras to record the eye position of human subjects, and hence, record pupil dilation and eye movements. The eyetracker puts a video cameras and infrared illuminators in front of the eye to record the position of the eye, cornea reflections, and the size of the pupil. Using the movements of one’s pupil (with respect to cornea reflections), the eye-tracker tracks the movement of one’s eyes, which is then mapped into locations on the screen by calibration and adjustments for head movements. With the eyetracker, we can measure gaze locations, the time length of fixations, and pupil dilation. Hence, using the eyetracker, we can investigate how fixations (looking at the same place for a while), saccades (fast eye movements) and pupil dilation responses (changes in pupil sizes) are related to the information on the screen and behavioral choices during an experiment. Understanding the relationship between these observables can help us understand how human behavior in the economy can be affected by what information people acquire, where their attention is focused on, what emotional state they are in, and even what brain activity they are engaged in. This is because fixations and saccades (matched with information shown on screen) indicate how people acquire information (and what they see), time lengths of fixations indicate attention, and pupil dilation responses indicate emotion, arousal, stress, pain, or cognitive load.