Figure 1. Photographs of the apparatus.

A subject is shown performing the experiment (left) along with a close-up of the goggles with eye tracking camera (right). In use, the head frame is adjusted to the seated height of each subject, and the monitor position adjusted to maintain a consistent distance to each subject's eyes. The base of the head frame is mechanically secured to the desk, but the upper part can be raised or lowered. The camera is mounted on a flexible arm that holds position once adjusted for a close-up view of the subject's eye. Experiment workstations and experimentor controls are not shown.