Equipment

Participants’ eye movements are monitored throughout the trial using a head-mounted eye tracker. (We are currently using the Eyelink II eye tracker, which samples eye coordinates with a frequency of 250 or 500 Hz.) The eye tracker consists of two miniature cameras that record the size of the pupil and the corneal reflection for each eye (which allows us to infer the position of the eye with respect to the head), as well as a camera recording the light reflection on a set of markers positioned on the monitor that displays the visual stimuli. By computing the position of the eyes with respect to the position of the markers, we can infer, in real time, the direction of participant’s eye gaze on a predefined area (the screen on which the visual stimuli are displayed).