By the use of television techniques it is possible to record the position of a man’s gaze upon a picture of the scene at which he is looking. The corneal reflection of a light is picked up by a television camera, which magnifies the movement of the spot about 100 times. The scene at which the man is gazing is provided by a second television camera, and the corneal reflection is superimposed upon another television monitor also showing the same scene. By suitable calibration, this spot can be made to lie upon that part of the scene being regarded and the accuracy with which this can be done is within one or two degrees.Thus it is possible to see where a man is looking at any moment, and simultaneously to record the composite eye-scene picture by means of a motion picture camera. In addition to its practical uses, this method is particularly useful for answering such general questions as whether a subject always sees what he is directly looking at, what kind of cues catch his attention when he is searching, and what sort of changes in a display catch his attention. It is primarily intended for use with a moving display, as it records the point of view directly on to each state of the display. Successive glances therefore indicate the order in which particular parts of complex displays are selected, as well as the exact moment at which the gaze changes to a new position.
J. F. MACKWORTH and N. H. MACKWORTH, "Eye Fixations Recorded on Changing Visual Scenes by the Television Eye-Marker," J. Opt. Soc. Am. 48, 439-444 (1958)